METABOLISM

EXSCHANGE OF MATERIALS. INTENSITY OF METABOLISM IN ORGANISM. PHYSIOLOGYCAL BASES OF RATIONAL NUTRITION.

 

 

Metabolism is the sum total of all chemical reactions involved in maintaining the living state of the cells, and thus the organism. In general metabolism may be divided into two categories: catabolism or the break down of molecules to obtain energy; and anabolism or the synthesis of all compounds needed by the cells (examples are DNA, RNA, an protein synthesis). The diagram on the left contains a summary of all the types of metabolism that will be examined. In this module, the electron transport chain is examined.

Bioenergetics is a term which describes the biochemical or metabolic pathways by which the cell ultimately obtains energy.

Nutrition is a science that deals with the relation of food substance to living things. In the study of nutrition, the following items must be considered:

a) bodily requirement for various substances;

b) function in body;

c) amount needed;

d) level below which poor health results.

Essential foods supply energy (calories) and supply the necessary chemicals which the body itself cannot synthesize. Food provides a variety of substances that are essential for the building, upkeep, and repair of body tissues, and for the efficient functioning of the body.

A complete diet must supply the elements; carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, and at least 18 other inorganic elements. The major elements are supplied in carbohydrates, lipids, and protein. In addition, at least 17 vitamins and water are necessary. If an essential nutrient is omitted from the diet, certain deficiency symptoms appear.

 

 

From the moment a bite of food enters the mouth, each morsel of nutrition within starts to be broken down for use by the body. So begins the process of metabolism, the series of chemical reactions that transform food into components that can be used for the body’s basic processes. Proteins, carbohydrates, and fats move along intersecting sets of metabolic pathways that are unique to each major nutrient. Fundamentally—if all three nutrients are abundant in the diet—carbohydrates and fats will be used primarily for energy while proteins provide the raw materials for making hormones, muscle, and other essential biological equipment.

 

 

Nutrients

         fuel for energy supply

         energy storages

Energy Systems

Energy transfer

High energy phosphates

         ATP

         ATP utilization

         other high energy phosphates

         ways to produce ATP

Electron transfer

         reduction equivalents

 

 

Energy supply for the body

Nutrients: Fuels for the body

There are different nutrients used to produce energy for the metabolism

 

         Carbohydrates:               16 kJ/g

         Fat:                                37 kJ/g

         Protein:                          17 kJ/g

Carbohydrates (CHO) can be metabolised under aerobic and anaerobic conditions

Proteins and fat require oxygen to be metabolised

Storing energy

The body gains ‘energy sources’ by the all day dietary uptake

…but the body even stores energy for times of starvation

         Fat                       79%

         Protein                  20%

         Carbohydrates      1%

most energy is stored as fat

Most of the energy used comes from CHO

 

 

Proteins in food are broken down into pieces (called amino acids) that are then used to build new proteins with specific functions, such as catalyzing chemical reactions, facilitating communication between different cells, or transporting biological molecules from here to there. When there is a shortage of fats or carbohydrates, proteins can also yield energy.

Fats typically provide more than half of the body’s energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty acids that aren’t needed right away are packaged in bundles called triglycerides and stored in fat cells, which have unlimited capacity. “We are really good at storing fat,” says Judith Wylie-Rosett, EdD, RD

Carbohydrates, on the other hand, can only be stored in limited quantities, so the body is eager to use them for energy. “We think of carbs as the [nutrient] that’s used first,” says Eric Westman, MD, MHS, director of the Lifestyle Medicine Clinic at Duke University Medical Center. “We can only store a day or two of carbs.” The carbohydrates in food are digested into small pieces—either glucose or a sugar that is easily converted to glucose—that can be absorbed through the small intestine’s walls. After a quick stop in the liver, glucose enters the circulatory system, causing blood glucose levels to rise. The body’s cells gobble up this mealtime bounty of glucose more readily than fat, says Wylie-Rosett.

 

 

1.                The catabolism of proteins, carbohydrates, and fats

Energy can be extracted from molecules more complex than glucose such as proteins, carbohydrates and fats. These complex molecules are broken down into monomers, which then enter glycolysis or the citric acid cycle at various positions.

·                     Disaccharides and polysaccharides are broken down into glucose for glycolysis; other molecules may require more processing.

·                     Proteins are broken down into amino acids, which are used by the cell to make new proteins; excess amino acids are converted for use in glycolysis or the citric acid cycle following deamination.

·                     Fats are broken down into glycerol and fatty acids. Fatty acids contain most of the energy in fats. Fats store almost twice as much energy as carbohydrates.

·                     Amino acids are used directly to create new proteins.

Energy supply for the body

Catabolic and anabolic metabolism

Catabolic metabolism is the break down or oxidation of nutrients

it releases energy

it produces intermediates that are useful for the metabolism

Once the cells have had their fill of glucose, the liver stores some of the excess for distribution between meals should blood glucose levels fall below a certain threshold. If there is leftover glucose beyond what the liver can hold, it can be turned into fat for long-term storage so none is wasted. When carbohydrates are scarce, the body runs mainly on fats. If energy needs exceed those provided by fats in the diet, the body must liquidate some of its fat tissue for energy.

While these fats are a welcome source of energy for most of the body, a few types of cells, such as brain cells, have special needs. These cells could easily run on glucose from the diet, but they can’t run on fatty acids directly. So under low-carbohydrate conditions, these finicky cells need the body to make fat-like molecules called ketone bodies. This is why a very-low-carbohydrate diet is sometimes called “ketogenic.” (Ketone bodies are also related to a dangerous diabetic complication called ketoacidosis, which can occur if insulin levels are far too low.) Ketone bodies could alone provide enough energy for the parts of the body that can’t metabolize fatty acids, but some tissues still require at least some glucose, which isn’t normally made from fat. Instead, glucose can be made in the liver and kidneys using protein from elsewhere in the body. But take care: If not enough protein is provided by the diet, the body starts chewing on muscle cells.

Anabolic metabolism produces or synthesises new components or substances i.e. enzymes, fat, hormones…

         This consumes energy

         It requires different precursors

Energy of the catabolic metabolism is used for the anabolic metabolism

Synthesized end products

Catabolic metabolism is the break down or oxidation of nutrients

it releases energy

it produces intermediates that are useful for the metabolism

Anabolic metabolism produces or synthesises new components or substances i.e. enzymes, fat, hormones…

         This consumes energy

         It requires different precursors

Energy of the catabolic metabolism is used for the anabolic metabolism

Synthesized end products       CHO, fats, proteins + O2

Catabolic metabolism of fats, proteins and carbohydrates can provide glucose for use in cellular respiration wheeeded. Glucose can be extracted from a variety of organic molecules.

Complex carbohydrates (polysaccharides and starches) are usually taken into cells once they have been digested into monosaccharides (primarily glucose and fructose). Once inside the cell, they can be converted to glucose (if necessary) and/or shuttled directly into glycolysis.

Proteins are digested into amino acids and simple derivative compounds outside the cell. Once the amino acids enter the cell, they typically are used for rebuilding other proteins, but amino acids can be deaminated (nitrogen group removed) and converted to glucose for entry into glycolysis when the cell has an excess of amino acids or a deficiency of available glucose.

Fats are catabolized by hydrolysis to free fatty acids and glycerol. The glycerol is converted into glyceraldehyde three-phosphate and enters glycolysis at the end of phase one. The fatty acids are broken down by beta oxidation to release acetyl-CoA, which then is fed into the citric acid cycle. Beta oxidation, which breaks fats into two-carbon fragments, also produces NADH and FADH_2, which can be used in the electron transport chain. Fatty acids release more energy (almost twice as much) upon oxidation than carbohydrates because carbohydrates contain more oxygen in their structures so they are already partially oxidized.

Green plants, algae and some bacteria are autotrophs, or “self-feeders.” Most of them use the energy of sunlight to assemble inorganic precursors, chiefly carbon dioxide and water, into the array of organic macromolecules of which they are made. The process is photosynthesis. Photosynthesis makes the ATP needed for the anabolic reactions in the cell.

All other organisms, including humans, are heterotrophs. They secure all their energy from organic molecules taken in from their surroundings (“food”). Although heterotrophs may feed partially (as most humans do), or exclusively on other heterotrophs, all the food molecules come ultimately from autotrophs. We may eat beef, but the steer had eaten grass.

Heterotrophs degrade some of the organic molecules they take in (catabolism) to make the ATP that they need to synthesize the others into the macromolecules of which they are made (anabolism). Anabolic processes use the organic molecules from food ingestion to build other molecules needed by the cell. For example, amino acids are used as monomers to create new proteins.

Complex carbohydrates and fats also are assembled from monosaccharides and fatty acids, respectively. Intermediate compounds from glycolysis and the citric acid cycle can be diverted into fat or carbohydrate building within the cell. These processes are endergonic, in that they consume ATP rather than generate it, but they also store energy in the chemical bonds created.

Energy systems

Main systems are:

Glycolysis

TCA- or Krebs-Cycle

Electron transport chain and oxidative phosphorylation

The systems are not isolated

They work together and parallel to each other

Energy systems

The different energy systems of the human body are used regarding to different energetic demands

 

The choice of the energy system is influence by the

 

         Supply velocity

         availability

         oxygen supply     

 

Energy transfer

Metabolic energy is generated by oxidizing different nutrients

Principally oxidation is similar to a combustion

C6H1206 + 6O2 à 6 CO2 + 6 H2O

This formula describes the over all reaction when the body ‘burns’ Glucose by aerobic glycolysis

The same formula can be used to describe the reaction when wood is burned in a fire

 

Energy transfer

In the cell the energy is released in many single portions

Controlled enzymatic reactions are used to convert and transfer the chemical energy of the oxidation to make it utilizable for the metabolism

 

High energy phosphates

Adenosine triphosphate

Energy of food oxidation is used to produce ATP that is used as a universal cellular energy ‘currency

High energy phosphates

ATP – Hydroysation

In the metabolism transfer of phosphate residues or hydrolysation of phosphate bonds is used to store, transfer and utilize   chemical energy

ATPase

ATP            ADP + Pi + energy

               work

mechanical                                   synthesis

                        transport                    

High energy phosphates

Myokinase reaction

ADP is still a ‘high energy phosphate’

It has…

         less energy than ATP

         but more than AMP

This fact is used by tissues with a high energy turnover like skeletal muscle

2 ADP                           ATP + AMP

From 2 ADP which cannot be used by the muscle                    (myosin ATPase)

1 ATP is produced that can be used!

Other high energetic phosphates

Beside ATP the other nucleotide triphosphates are used:

         GTP, UTP, CTP there are other high energy phosphates:

intermediates of the Glycolysis

         1,3-diphosphoglycerate

         phosphoenol pyruvate

Creatine-Phosphate as energy reservoir in the skeletal muscle (phosphagen system

Creatine phosphate: the phosphagen system

The working skelketal muscle has a very high ATP turn over

The phosphagen or creatine kinase system enables the fast regeneration of ATP from Creatine phosphate and ADP in situations with an exceeding ATP demand

CrP + ADP           Cr + ATP

Under resting condition Creatine phosphate is regenerated by the reverse reaction

 

 

Production of ATP

There are two different ways to produce ATP from ADP and Pi

Substrate level phosphorylation

energy of the oxidation is directly converted by transferring a phosphate (Pi) from an intermediate (Phosphoenol pyruvate) to ADP

(Glycolysis and Citric acid cycle)

Oxidative phosphorylation

Energy of oxidation is used to produce reduction equivalents these are oxidized in the mitochondria by oxygen

This energy is indirectly used to produce ATP

 

Electron transfer

Oxidation/Reduction

Reduction equivalents are the ‘second energy currency’ of the cell

They are used to transport electrons (e-) from the nutrient to the final oxidizing agents (in human O2)

The most important reduction equivalents are

         NAD+

         FAD

         NADP+

The electron from NADPH + H+  reduction are not used to produce ATP but for the anabolic metabolism

Conclusions

Carbohydrates, fat or proteins are used to generate metabolic energy

Different systems work together to guarantee sufficient energy supply under different physiological conditions

Nutrients are oxidized and the energy is used to produce ATP and or other high energy phosphates

ATP can be produced by substrate level phosphorylation or by oxidative phosphorylation

Electron transport especially to the electron transport chain is important for energy utilisation

1. Metabolism of proteins

a) Physiological meaning of proteins (1. All enzymes are protein. 2. All moving in organism provide with cooperation of contractive proteins. 3. Proteins have plastic and energy function. 4. Proteins enter to hormones composition. 5. Proteins enter to the cells’ membrane structure.).

b) Transformation of proteins in human organism (Protein enter to our organism with food. Then they pass through digestive tract, absorbed in blood in amino acids case. Some quantity goes to the cells of different tissues, other to liver. In liver from it synthesis enzymes and protein of blood plasma. It is pereamine processes; by way of desaminate formed ammonium (NH₃) and ketonic acids. From ammonium formed urea and then urine acid. It and proteins of tissues formed blood rest nitrogen, which go to kidney and excreted in case of urine nitrogen. Ketonic acids oxide and from them synthesize glycogen and fat acids.)

c) Nitrogen balance (Iorm quantity of nitrogen which come to organism (with proteins) must be equal quantity of nitrogen, which go out from organism (with urine, feces and perspiration. Nitrogen balance is the ratio of nitrogen quantity, which enters in organism with food and distinguished by kidney, digestive tract, glands. In protein is 16 % of nitrogen. One gram of nitrogen is present in 6,25 gram of protein. In adult iorm must be nitrogen balance.).

d) Minimum of proteins, optimum of proteins, biological value of proteins (Minimum of proteins is minimal quantity of protein in which save nitrogen balance; It daily quantity is near 50 gram of protein. Optimum of proteins is a quantity of protein in food, which completely secure necessity of organism. It is 80-100 grams of protein. Biological value of proteins: one gram of protein gives to organism 4,1 kcal of energy. In daily quantity must be including amino acids, which are do not syntheses in organism.).

e) Regulation of proteins metabolism (Central mechanism of regulation act on hypothalamus. It activates pituitary gland, they produce growth hormone; activate thyroid glands and adrenal glands. Hypothalamus has parasympathetic and sympathetic centers. Parasympathetic influences, growth hormone, insulin, thyroid hormones, glucocorticoids (in liver) have anabolic effect. Sympathetic influences, glucocorticoids (in muscles, lymph tissues) have katabolic effect.)

All life requires protein since it is the chief tissue builder and part of every cell in the body. Among other functions, proteins help to: make hemoglobin in the blood that carries oxygen to the cells; form anti-bodies that fight infection; supply nitrogen for DNA and RNA genetic material; and supply energy.

Proteins are necessary for nutrition because they contain amino acids. Among the 20 or more amino acids, the human body is unable to synthesize 8, therefore, these amino acids are called essential amino acids. A food containing protein may be of poor biological value if it is deficient in one or more of the 8 essential amino acids: lysine, tryptophan, methionine, leucine, isoleucine, phenylalanine, valine, and threonine. Proteins of animal origin have the highest biological value because they contain a greater amount of the essential amino acids. Foods with the best quality protein are listed in diminishing quality order: whole eggs, milk, soybeans, meats, vegetables, and grains.

Proteins contain carbon, hydrogen, oxygen, nitrogen, and sometimes other atoms. They form the cellular structural elements, are biochemical catalysts, and are important regulators of gene expression. Nitrogen is essential to the formation of twenty different amino acids, the building blocks of all body cells. Amino acids are characterized by the presence of a terminal carboxyl group and an amino group in the alpha position, and they are connected by peptide bonds.

Digestion breaks protein down to amino acids. If amino acids are in excess of the body’s biological requirements, they are metabolized to glycogen or fat and subsequently used for energy metabolism. If amino acids are to be used for energy their carbon skeletons are converted to acetyl CoA, which enters the Krebs cycle for oxidation, producing ATP. The final products of protein catabolism include carbon dioxide, water, ATP, urea, and ammonia.

Vitamin B₆ is involved in the metabolism (especially catabolism) of amino acids, as a cofactor in transamination reactions that transfer the nitrogen from one keto acid (an acid containing a keto group ‘-CO-’ in addition to the acid group) to another. This is the last step in the synthesis of nonessential amino acids and the first step in amino acid catabolism. Transamination converts amino acids to L-glutamate, which undergoes oxidative deamination to form ammonia, used for the synthesis of urea. Urea is transferred through the blood to the kidneys and excreted in the urine.

The glucose-alanine cycle is the main pathway by which amino groups from muscle amino acids are transported to the liver for conversion to glucose. The liver is the main site of catabolism for all essential amino acids, except the branched-chain amino acids, which are catabolized mainly by muscle and the kidneys. Plasma amino-acid levels are affected by dietary carbohydrate through the action of insulin, which lowers plasma amino-acid levels (particularly the branched-chain amino acids) by promoting their entry into the muscle.

Body proteins are broken down when dietary supply of energy is inadequate during illness or prolonged starvation. The proteins in the liver are utilized in preference to those of other tissues such as the brain. The gluconeogenesis pathway is present only in liver cells and in certain kidney cells.

Disorders of amino acid metabolism include phe-nylketonuria, albinism, alkaptonuria, type 1 tyrosi-naemia, nonketotic hyperglycinaemia, histidinaemia, homocystinuria, and maple syrup urine disease.

The 20 Amino Acids and What They Do!

 

 

 

 Metabolism of fats

Fats contain mostly carbon and hydrogen, some oxygen, and sometimes other atoms. The three main forms of fat found in food are glycerides (principally triacylglycerol ‘triglyceride’, the form in which fat is stored for fuel), the phospholipids, and the sterols (principally cholesterol). Fats provide 9 kilocalories per gram (kcal/g), compared with 4 kcal/g for carbohydrate and protein. Triacylglycerol, whether in the form of chylomicrons (microscopic lipid particles) or other lipoproteins, is not taken up directly by any tissue, but must be hydrolyzed outside the cell to fatty acids and glycerol, which can then enter the cell.

Fatty acids come from the diet, adipocytes (fat cells), carbohydrate, and some amino acids. After digestion, most of the fats are carried in the blood as chylomicrons. The main pathways of lipid metabolism are lipolysis, betaoxidation, ketosis, and lipogenesis.

Lipolysis (fat breakdown) and beta-oxidation occurs in the mitochondria. It is a cyclical process in which two carbons are removed from the fatty acid per cycle in the form of acetyl CoA, which proceeds through the Krebs cycle to produce ATP, CO₂, and water.

Ketosis occurs when the rate of formation of ketones by the liver is greater than the ability of tissues to oxidize them. It occurs during prolonged starvation and when large amounts of fat are eaten in the absence of carbohydrate.

Fats are concentrated sources of energy because they give twice as much energy as either carbohydrates or protein on a weight basis. The functions of fats are to: make up part of the structure of cells, form a protective cushion and heat insulation around vital organs, carry fat soluble vitamins, and provide a reserve storage for energy.

Three unsaturated fatty acids which are essential include: linoleic, linolinic, and arachidonic and have 2, 3, and 4 double bonds respectively. Saturated fats, along with cholesterol, have been implicated in arteriosclerosis, “hardening of the arteries”. For this reason, the diet should be decreased in saturated fats (animal) and increased in unsaturated fat (vegetable).

Cholesterol Metabolism

Cholesterol is either obtained from the diet or synthesized in a variety of tissues, including the liver, adrenal cortex, skin, intestine, testes, and aorta. High dietary cholesterol suppresses synthesis in the liver but not in other tissues.

Carbohydrate is converted to triglyceride utilizing glycerol phosphate and acetyl CoA obtained from glycolysis. Ketogenic amino acids, which are metabolized to acetyl CoA, may be used for synthesis of triglycerides. The fatty acids cannot fully prevent protein breakdown, because only the glycerol portion of the triglycerides can contribute to gluconeogenesis. Glycerol is only 5% of the triglyceride carbon.

Most of the major tissues (e.g., muscle, liver, kidney) are able to convert glucose, fatty acids, and amino acids to acetyl-CoA. However, brain and nervous tissue—in the fed state and in the early stages of starvation—depend almost exclusively on glucose. Not all tissues obtain the major part of their ATP requirements from the Krebs cycle. Red blood cells, tissues of the eye, and the kidney medulla gain most of their energy from the anaerobic conversion of glucose to lactate.

a) Physiological meaning of fats (1. Fat enter to the cells’ membrane structure. 2. Fat necessary to the structure of steroid hormones. 3. Fats is a spring of energy.).

b) Transformation of fats in human organism (Fats enter in our organism with food (threeglycerides). It absorbed in case of fat acids with short and long chains and glycerin from digestive tract. Fat acids with short chain and glycerin go in blood, then to fat depo, heart, liver. Fat acids with long chain go into mucus shell of intestine, where threeglycerides absorbed in chilimicrones case. Then they go to lymph and blood.)

c) Regulation of fats metabolism (Central mechanism of regulation act on hypothalamus. It is activate hypophysis, which produce growth hormone; activate thyroid glands and adrenal glands. Hypothalamus has parasympathetic and sympathetic centers. Parasympathetic influences, insulin, glucocorticoids have anabolic effect. Sympathetic influences, thyroid hormones, glukagon, epinephrine, growth hormone have katabolic effect.)

3. Metabolism of carbohydrates

Foods supply carbohydrates in three forms: starch, sugar, and cellulose (fiber). Starch and sugar are major and essential sources of energy for humans. A lack of carbohydrates in the diet would probably result in an insufficient number of calories in the diet. Cellulose furnishes bulk in the diet.

Since the tissues of the body need glucose at all times, the diet must contain substances such as carbohydrates or substances which will yield glucose by digestion or metabolism. For the majority of the people in the world, more than half of the diet consists of carbohydrates from rice, wheat, bread, potatoes, macaroni.

 

Carbohydrates made up of carbon, hydrogen, and oxygen atoms are classified as mono-, di-, and poly-saccharides, depending on the number of sugar units they contain. The monosaccharides—glucose, galactose, and fructose—obtained from the digestion of food are transported from the intestinal mucosa via the portal vein to the liver. They may be utilized directly for energy by all tissues; temporarily stored as glycogen in the liver or in muscle; or converted to fat, amino acids, and other biological compounds.

Carbohydrate metabolism plays an important role in both types of diabetes mellitus. The entry of glucose into most tissues—including heart, muscle, and adipose tissue—is dependent upon the presence of the hormone insulin. Insulin controls the uptake and metabolism of glucose in these cells and plays a major role in regulating the blood glucose concentration. The reactions of carbohydrate metabolism cannot take place without the presence of the B vitamins, which function as coenzymes. Phosphorous, magnesium, iron, copper, manganese, zinc, and chromium are also necessary as cofactors.

Carbohydrate metabolism begins with glycolysis, which releases energy from glucose or glycogen to form two molecules of pyruvate, which enter the Krebs cycle (or citric acid cycle), an oxygen-requiring process, through which they are completely oxidized. Before the Krebs cycle can begin, pyruvate loses a carbon dioxide group to form acetyl coenzyme A (acetyl-CoA). This reaction is irreversible and has important metabolic consequences. The conversion of pyruvate to acetyl-CoA requires the B vitamins.

The hydrogen in carbohydrate is carried to the electron transport chain, where the energy is conserved in ATP molecules. Metabolism of one molecule of glucose yields thirty-one molecules of ATP. The energy released from ATP through hydrolysis (a chemical reaction with water) can then be used for biological work.

Only a few cells, such as liver and kidney cells, can produce their own glucose from amino acids, and only liver and muscle cells store glucose in the form of glycogen. Other body cells must obtain glucose from the bloodstream.

Glycogenesis is the conversion of excess glucose to glycogen. Glycogenolysis is the conversion of glycogen to glucose (which could occur several hours after a meal or overnight) in the liver or, in the absence of glucose-6-phosphate in the muscle, to lactate. Gluco-neogenesis is the formation of glucose from noncarbo-hydrate sources, such as certain amino acids and the glycerol fraction of fats when carbohydrate intake is limited. Liver is the main site for gluconeogenesis, except during starvation, when the kidney becomes important in the process. Disorders of carbohydrate metabolism include diabetes mellitus, lactose intolerance, and galactosemia.

As already mentioned, metabolism refers to the chemical reactions carried out inside of the cell. The major metabolic reactions which we will study are those involving catabolism which is the breakdown of larger molecules to extract energy. We will focus our discussion on the individual steps in the metabolic reactions where energy is produced. Some attention will also be given to the synthesis of other biomolecules.

The overall reaction for the combustion of glucose is written:

C₆H₁₂O₆ + 6 O₂ —–> 6 CO₂ + 6 H₂O + energy

Although the above equation represents the overall metabolic reaction for carbohydrates, there are actually over thirty individual reactions. Each reaction is controlled by a different enzyme. The failure of an enzyme to function may have serious and possibly fatal consequences. Slightly less than half of the 686 kcal/mole of the energy produced by combustion is available for storage and use by the cell with the remaining amount dissipated as heat.

Metabolism will be studied in various parts. Interrelationships will be pointed out as they are encountered. Just as there are three basic biomolecules – carbohydrates, lipids, and proteins, the metabolism of each of these will be studied individually. The interrelationships of the major components in metabolism are diagramed in Figure 1. At the end of the study of metabolism, you may be asked to diagram portions of it from memory.

 

 

 

a) Physiological meaning of carbohydrates (1. Carbohydrates are a main spring of energy. 2. Carbohydrates are the part of some enzymes.).

 

b) Transformation of carbohydrates in human organism (Carbohydrates enter in our organism with food. It absorbed in case of glucose from digestive tract. Glucose goes in blood, then in brain, liver and muscles. Depo of glycogen are in liver and muscles in rest condition. In working muscles they divide to lactic acid, water and CO₂.).

 

c) Regulation of carbohydrates metabolism (Central mechanism of regulation act on hypothalamus. It is activate hypophysis, which produce growth hormone; activate thyroid glands and adrenal glands. Hypothalamus has parasympathetic and sympathetic centers. Parasympathetic influences, insulin has anabolic effect. Sympathetic influences, growth hormone, glucocorticoids, thyroid hormones, glukagon, epinephrine have katabolic effect.)

Regulation of metabolism is ultimately regulation of the enzyme catalysts in

pathways.

There are various kinds of regulation to be considered, all of which are

important and often interact in intermediary metabolism.

First, the amount of an enzyme can be increased or decreased, by changing its rate of synthesis at the transcriptional, translational, or post-translational stage, or its rate of degradation.

Second, changes in the concentration of the substrate (provided it is at or below the KM) can affect the rate of the reaction.

Third, an enzyme can be regulated by metabolites that are inhibitors or activators binding to its catalytic or allosteric/regulatory sites.

Fourth, an enzyme can be inhibited or activated by covalent modification, in particular by phosphorylation by protein kinases, some of which mediate hormonal actions. In addition, the importance of other types of covalent modification, such as acetylation, acylation, adenylylation, and methylation, is increasingly recognized.

Fifth, an enzyme can be inhibited or activated by protein–protein interactions with specific protein regulators.

Sixth, an enzyme’s functional activity can be affected by compartmentation within the cell and thus controlled by translocation from one area to another. Finally, different tissues may exhibit differences in metabolism despite identical or nearly identical pathways, because of the presence of isozymes, that is, enzymes that catalyze the same reaction but are different proteins and thus can have different kinetic and regulatory properties, due to differences in the catalytic site and in regulatory sites for noncovalent and covalent regulation. Nutritional and hormonal states are intertwined in affecting intermediary metabolism. Food intake raises the level of the key peptide hormone insulin, which is synthesized in and secreted from the b-cells of the pancreatic islets primarily in response to glucose. However, fatty acids and some amino acids can potentiate the secretory response, as can certain gut hormones such as glucagon-like peptide (GLP)-1.

Insulin is the primary regulator of whole body carbohydrate metabolism. Increases in its concentration activate glucose uptake in muscle and fat cells, inhibit glucose synthesis (gluconeogenesis) and glucose output by the liver, and stimulate glucose storage into glycogen, whereas decreases in its concentration have the opposite effect.

In addition, insulin promotes other kinds of fuel storage, by stimulating triglyceride synthesis and inhibiting lipolysis (triglyceride breakdown) and by similar effects on protein synthesis and degradation. A number of counterregulatory hormones oppose the action of insulin, including the peptide hormone glucagon, which is secreted from the a-cells of the pancreatic islets in response to low blood glucose and promotes hepatic glycogen breakdown and gluconeogenesis as well as adipose tissue lipolysis, and the catecholamine epinephrine (adrenaline), which is secreted from the adrenal glands in response to various excitatory stimuli and promotes glycogen breakdown and lipolysis. In subjects with diabetes, a lack of insulin or resistance to its action leads to high blood glucose levels due to impaired glucose disposal (primarily into muscle glycogen) and unrestrained hepatic glucose output.

Also contributing to these abnormalities are excessive lipolysis and hence circulating fatty acid levels and increased protein

Vitamins

Vitamins and minerals make people’s bodies work properly. Although you get vitamins and minerals from the foods you eat every day, some foods have more vitamins and minerals than others.

Vitamins fall into two categories: fat soluble and water soluble. The fat-soluble vitamins — A, D, E, and K — dissolve in fat and can be stored in your body. The water-soluble vitamins — C and the B-complex vitamins (such as vitamins B6, B12, niacin, riboflavin, and folate) — need to dissolve in water before your body can absorb them. Because of this, your body can’t store these vitamins. Any vitamin C or B that your body doesn’t use as it passes through your system is lost (mostly when you pee). So you need a fresh supply of these vitamins every day.

Whereas vitamins are organic substances (made by plants or animals), minerals are inorganic elements that come from the soil and water and are absorbed by plants or eaten by animals. Your body needs larger amounts of some minerals, such as calcium, to grow and stay healthy. Other minerals like chromium, copper, iodine, iron, selenium, and zinc are called trace minerals because you only need very small amounts of them each day.

Vitamins and minerals boost the immune system, support normal growth and development, and help cells and organs do their jobs. For example, you’ve probably heard that carrots are good for your eyes. It’s true! Carrots are full of substances called carotenoids that your body converts into vitamin A, which helps prevent eye problems.

Another vitamin, vitamin K, helps blood to clot (so cuts and scrapes stop bleeding quickly). You’ll find vitamin K in green leafy vegetables, broccoli, and soybeans. And to have strong bones, you need to eat foods such as milk, yogurt, and green leafy vegetables, which are rich in the mineral calcium.

People go through a lot of physical changes — including growth and puberty — during their teenage years. Eating right during this time is especially important because the body needs a variety of vitamins and minerals to grow, develop, and stay healthy.

Eating a variety of foods is the best way to get all the vitamins and minerals you need each day, as well as the right balance of carbohydrates, proteins, fats, and calories. Whole or unprocessed foods — like fresh fruits and vegetables, whole grains, low-fat dairy products, lean meats, fish, and poultry — are the best choices for providing the nutrients your body needs to stay healthy and grow properly.

It’s OK to eat foods like potato chips and cookies once in a while, but you don’t want to overdo high-calorie foods like these that offer little nutritionally.

To choose healthy foods, check food labels and pick items that are high in vitamins and minerals. For example, if you’re choosing beverages, you’ll find that a glass of milk is a good source of vitamin D and the minerals calcium, phosphorous, and potassium. A glass of soda, on the other hand, offers very few vitamins or minerals — if any.

You can also satisfy your taste buds without sacrificing nutrition while eating out: Vegetable pizzas or fajitas, sandwiches with lean cuts of meat, fresh salads, and baked potatoes are just a few delicious, nutritious choices.

If you’re a vegetarian, you’ll need to plan carefully for a diet that offers the vitamins and minerals found primarily in meats. The best sources for the minerals zinc and iron are meats, fish, and poultry. However, you can get zinc and iron in dried beans, seeds, nuts, and leafy green vegetables like kale.

Vitamin B12, which is important for manufacturing red blood cells, is not found in plant foods. If you don’t eat meat, you can find vitamin B12 in eggs, milk and other dairy foods, and fortified breakfast cereals. Vegans (vegetarians who eat no animal products at all, including dairy products) may need to take vitamin supplements. If you’re thinking about becoming a vegetarian, talk to your doctor or a registered dietitian about how to plan a healthy, balanced diet.

Micronutrients with a big role in the body

Vitamins and minerals are often called micronutrients because your body needs only tiny amounts of them. Yet failing to get even those small quantities virtually guarantees disease. Here are a few examples of diseases that can result from vitamin deficiencies:

·                     Scurvy. Old-time sailors learned that living for months without fresh fruits or vegetables — the main sources of vitamin C — causes the bleeding gums and listlessness of scurvy.

·                     Blindness. In some developing countries, people still become blind from vitamin A deficiency.

·                     Rickets. A deficiency in vitamin D can cause rickets, a condition marked by soft, weak bones that can lead to skeletal deformities such as bowed legs. Partly to combat rickets, the U.S. has fortified milk with vitamin D since the 1930s.

Just as a lack of key micronutrients can cause substantial harm to your body, getting sufficient quantities can provide a substantial benefit. Some examples of these benefits:

·                     Strong bones. A combination of calcium, vitamin D, vitamin K, magnesium, and phosphorus protects your bones against fractures.

·                     Prevents birth defects. Taking folic acid supplements early in pregnancy helps prevent brain and spinal birth defects in offspring.

·                     Healthy teeth. The mineral fluoride not only helps bone formation but also keeps dental cavities from starting or worsening.

The difference between vitamins and minerals

Although they are all considered micronutrients, vitamins and minerals differ in basic ways. Vitamins are organic and can be broken down by heat, air, or acid. Minerals are inorganic and hold on to their chemical structure.

So why does this matter? It means the minerals in soil and water easily find their way into your body through the plants, fish, animals, and fluids you consume. But it’s tougher to shuttle vitamins from food and other sources into your body because cooking, storage, and simple exposure to air can inactivate these more fragile compounds.

Vitamins

Vitamins are organic compounds that are essential for our body to function properly. Most vitamins are obtained from what you consume, because the body is unable to manufacture most of the essential vitamins that you need to survive. Here are types of vitamins and their roles:

 

a)    Physiological meaning of water-solution vitamins

Vitamin C take place in oxygen-reducing metabolic processes in organism, develop of kolagen of blood vessels’ wall, increase antitoxic function of liver. Vitamin B₁ takes place in metabolism of carbohydrates, protein and fats, secure normal growth, increases motor and secretor function of stomach, normalized heart activity. Vitamin B₂ takes place in growth and development of fetus and child. Vitamin B₆ takes place in protein metabolism, fat metabolism, influence on development of blood component

Food sources: Good sources of vitamin B6 include fortified cereals, beans, poultry, fish, and some vegetables and fruits, especially dark leafy greens, papayas, oranges, and cantaloupe.

In 1968, a Boston pathologist investigated the deaths of two children from massive strokes. Both had inherited conditions that caused them to have extremely high levels of a protein breakdown product in their blood, and both had arteries as clogged with cholesterol as those of a 65-year-old fast-food addict. Putting one and one together, he hypothesized that lower, but still elevated levels of this breakdown product—called homocysteine—would contribute to the artery-clogging process of atherosclerosis.

Folate, vitamin B6, and vitamin B12 play key roles in converting homocysteine into methionine, one of the 20 or so building blocks from which the body builds new proteins. Without enough folate, vitamin B6, and vitamin B12, this conversion process becomes inefficient and homocysteine levels increase. In turn, increasing intake of folate, vitamin B6, and vitamin B12 decreases homocysteine levels.

Since these early observations about homocysteine, most but not all studies have linked high levels of homocysteine with a modest increase in risk of heart disease and stroke. And some but not all observational studies, including the Nurses’ Health Study, show lower risks of cardiovascular disease, stroke, and hypertension among people with higher intakes of folate, those who use multivitamin supplements, or those with higher levels of serum folate (the form of folate found in the body). But linking higher homocysteine levels—and lower folate levels—with heart disease risk does not necessarily mean that lowering homocysteine by taking folate and other B vitamins will lower risk. Ideally, this would be tested in randomized trials.

Several large randomized trials of B vitamins to lower homocysteine and prevent heart disease and stroke have failed to find any benefit. These trials had similar designs: Adults who had a history of heart disease or stroke, or who were at a very high risk of heart disease were given a pill containing high doses of vitamins B6, B12, and folic acid or a placebo. The studies found that taking high doses of the three B vitamins lowered homocysteine levels but did not lead to a reduction in coronary heart events.

But looking at cardiovascular disease as a whole may have obscured a potential benefit of at least one of the B vitamins, and studying people who already have advanced vascular disease may be too late in the process: The most recent analysis of multiple studies suggests that folic acid supplements can reduce the risk of stroke in people who have not already suffered a stroke, but they do not reduce the risk of second stroke in people who have already had one. Folic acid supplements were most protective in studies that lasted at least three years and that combined folic acid with vitamins B6 and B12. Trials that enrolled more men than women also showed more of a benefit, perhaps because men are at higher risk of stroke in general.

. Vitamin B₁₂ necessary for hemopoiesis.).

b)    Physiological action of fat-solution vitamins

Vitamin A secure normal growth and development, take place in vision pigment synthesis, secure adaptation of eyes to light.

 

Vitamin A does much more than help you see in the dark. It stimulates the production and activity of white blood cells, takes part in remodeling bone, helps maintain the health of endothelial cells (those lining the body’s interior surfaces), and regulates cell growth and division. This latter role had researchers exploring for years the relationship between vitamin A and cancer. Specifically, researchers looked at whether people could reduce their cancer risk by taking supplements of beta-carotene, one of several precursor compounds that the body can transform into vitamin A, or by taking the active form of vitamin A (also called retinol or preformed vitamin A). Several studies and randomized trials have dashed this hypothesis.

The Institute of Medicine’scurrent recommended intake of vitamin A is 900 micrograms of retinolfor men (equivalent to 3,000 IU) and 700 micrograms of retinol forwomen (equivalent to 2,333 IU). The upper limit for vitamin A intake from retinol is 3,000 micrograms, but intakes this high may increase the risk of hip fracture or interfere with the beneficial actions of vitamin D.

Food sources: Many breakfast cereals, juices, dairy products, and other foods arefortified with retinol (also known as preformed vitamin A). Many fruits and vegetables, andsome supplements, also contain beta-carotene and other vitamin Aprecursors, which the body can turn into vitamin A. It’s best to choose a multivitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene.

Although it’s possible to get too little vitamin A, it’s easy to get too much preformed vitamin A (retinol) from supplements. Intake of up to 3,000 micrograms of preformed vitamin A, more than three times the current recommended daily level, is thought to be safe. However, there is some evidence that this much preformed vitamin A might increase the risk of hip fracture or some birth defects. Another reason to avoid too much preformed vitamin A is that it may interfere with the beneficial actions of vitamin D.

In contrast to preformed vitamin A, beta-carotene is not toxic even at high levels of intake. The body can form vitamin A from beta-carotene as needed, and there is no need to monitor intake levels, as there is with preformed vitamin A. Therefore, it is preferable to choose a multivitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene; many multivitamin manufacturers have already reduced the amount of preformed vitamin A in their products. Smokers should avoid high-dose single supplements of beta-carotene, since some randomized trials in smokers have linked high dose supplementation with increased lung cancer risk. (5-7) There is no strong reason for anyone to take separate beta-carotene supplements.

 Vitamin D regulate metabolism of calcium and phosphorus. Vitamin E has antitoxic effect on cells lipids. Vitamin K secures normal hemostasis processes.).

Rather than slipping easily into the bloodstream like most water-soluble vitamins, fat-soluble vitamins gain entry to the blood via lymph channels in the intestinal wall (see illustration). Many fat-soluble vitamins travel through the body only under escort by proteins that act as carriers.

Absorption of fat-soluble vitamins

1.                 Food containing fat-soluble vitamins is ingested.

2.                 The food is digested by stomach acid and then travels to the small intestine, where it is digested further. Bile is needed for the absorption of fat-soluble vitamins. This substance, which is produced in the liver, flows into the small intestine, where it breaks down fats. Nutrients are then absorbed through the wall of the small intestine.

3.                 Upon absorption, the fat-soluble vitamins enter the lymph vessels before making their way into the bloodstream. In most cases, fat-soluble vitamins must be coupled with a protein in order to travel through the body.

4.                 These vitamins are used throughout the body, but excesses are stored in the liver and fat tissues.

5.                 As additional amounts of these vitamins are needed, your body taps into the reserves, releasing them into the bloodstream from the liver.

Fatty foods and oils are reservoirs for the four fat-soluble vitamins. Within your body, fat tissues and the liver act as the main holding pens for these vitamins and release them as needed.

To some extent, you can think of these vitamins as time-release micronutrients. It’s possible to consume them every now and again, perhaps in doses weeks or months apart rather than daily, and still get your fill. Your body squirrels away the excess and doles it out gradually to meet your needs.

Minerals

Minerals are atoms of certain chemical elements that are essential for body processes. Minerals are inorganic, meaning that they do not contain the element carbon. They are either produced by our body, or we obtain them by eating certain foods that contain them. They are ions found in blood plasma and cell cytoplasm, such as sodium, potassium, and chloride. In addition, minerals represent much of the chemical composition of bones (calcium, phosphorus, oxygen). They also contribute to nerve and muscle activity (sodium, potassium, calcium). Minerals serve several many other functions as well. There are 21 minerals considered essential for our bodies. Nine of the essential minerals in the body account for less than .01% of your body weight. Because of the small amount of these minerals that our body needs, we call them trace minerals. The 12 most important minerals and their functions are listed below:

 

 

Methods of studying organisms’ energy expenditure

a)              Method of direct calorimetry

The energy released by combustion of foodstuffs outside the body can be measured directly by oxidizing the compounds in an apparatus such as a bomb calorimeter, a metal vessel surrounded by water inside an insulated container. The food is ignited by an electric spark. The change in the temperature of the water is a measure of the calories produced. Similar measurements of the energy released by combustion of compounds in humans are much more complex, but calorimeters have been constructed that can physically accommodate human beings. The heat produced by their bodies is measured by the change in temperature of the water circulating through the calorimeter.

 

Calorimeter

 

 

 

b) Meaning of “respiratory quotient” (RQ), “caloric equivalent of oxygen” (The respiratory quotient is the ratio of the volume of CO₂ produced to the volume of O₂ consumed per unit of time. The RQ of carbohydrate is 1,00; for fat is about 0,7; for protein is about 0,8. Caloric equivalent of oxygen is a quantity of heat, which are take out after consuming of one liter of oxygen.)

A method of determining a respiratory parameter for a subject using an indirect calorimeter is provided. The indirect calorimeter includes a respiratory connector for passing inhaled and exhaled gases, a flow pathway operable to receive and pass inhaled and exhaled gases having a flow tube within the flow pathway through which the inhaled and exhaled gases pass, a flow meter for determining an instantaneous flow volume of the inhaled and exhaled gases, a component gas concentration sensor for determining an instantaneous fraction of a predetermined component gas and a computation unit having a processor and a memory. The method includes the steps of initializing the indirect calorimeter and the subject breathing into the respiratory connector if the indirect calorimeter is initialized, sensing the flow volume of the inhaled and exhaled gases passing through the flow pathway using the flow meter and transmitting a signal representing the sensed flow volume to the computation unit. The method also includes the steps of sensing a concentration of a predetermined component gas as the inhaled and exhaled gases pass through the flow pathway using the component gas sensor, and transmitting a signal representing the sensed concentration of the predetermined component gas to the computation unit. The method further includes the steps of calculating at least one respiratory parameter for the subject as the subject breathes through the calorimeter using the sensed flow volume and the sensed concentration of the predetermined component gas, and providing the subject with the at least one respiratory parameter.

 

b)    Method of indirect calorimetry with the complete gas analyses

Energy production can also be calculated by measuring the products of the energy-producting biologic oxidations – the CO₂, H₂O, the end products of protein catabolism produced or by measuring the O₂ consumed. When we measurement of O₂ consumption and of CO₂ distinguished it is the method of indirect calorimetry with the complete gas analyses. This is Duglas method.).

The present invention is a method for using an indirect calorimeter for measuring the metabolic rate of a subject. The calorimeter includes a respiratory connector configured to be supported in contact with the subject so as to pass inhaled and exhaled gases as the subject breathes. A flow pathway is operable to receive and pass inhaled and exhaled gases. A first end of the flow pathway is in fluid communication with the respiratory connector and a second end is in fluid communication with a source and sink for respiratory gases which may be either the ambient atmosphere, a mechanical ventilator, or other gas mixture source. A flow meter generates electrical signals as a function of the instantaneous flow volume of inhaled and exhaled gases passing through the flow pathway.

A component gas concentration sensor generates electrical signals as a function of the instantaneous fraction of a predetermined component gas in the inhaled and/or exhaled gases as the gases pass through the flow pathway. A computation unit receives the electrical signals from the flow meter and the component gas concentration sensor and calculates at least one respiratory parameter for the subject as the subject breathes through the calorimeter.

A method of determining a respiratory parameter for a subject using an indirect calorimeter includes the steps of initializing the indirect calorimeter and the subject breathing into the respiratory connector if the indirect calorimeter is initialized, sensing the flow volume of the inhaled and exhaled gases passing through the flow pathway using the flow meter and transmitting a signal representing the sensed flow volume to the computation unit. The method also includes the steps of sensing a concentration of a predetermined component gas as the inhaled and exhaled gases pass through the flow pathway using the component gas sensor, and transmitting a signal representing the sensed concentration of the predetermined component gas to the computation unit. The method further includes the steps of calculating at least one respiratory parameter for the subject as the subject breathes through the calorimeter using the sensed flow volume and the sensed concentration of the predetermined component gas, and providing the subject with the at least one respiratory parameter.

In some embodiments, the flow pathway includes a flow tube through which the inhaled and exhaled gases pass and a chamber disposed between the first end of the pathway and the flow tube. The chamber surrounds one end of the flow tube and forms a concentric chamber.

In other embodiments, a flow tube forms part of the flow pathway and is disposed between the two ends of the pathway. The first end of the pathway takes the form of an inlet conduit that extends perpendicularly to the flow tube.

In some embodiments, the flow pathway includes an elongated flow tube through which inhalation and exhalation gases pass. The flow meter is an ultrasonic flow meter and includes two spaced apart ultrasonic transducers. The transducers are each aligned with the elongated flow tube such that ultrasonic pulses transmitted between the transducers travel in a path that is generally parallel to the flow of fluid in the flow tube.

Yet other embodiments of the present invention are also disclosed in the following description and the accompanying figures.

The body’s generation of heat is known as thermogenesis and it can be measured to determine the amount of energy expended. BMR generally decreases with age and with the decrease in lean body mass (as may happen with aging). Increasing muscle mass increases BMR, although the effect is not significant enough to act as a weight-loss method. Aerobic fitness level, a product of cardiovascular exercise, while previously thought to have effect on BMR, has been shown in the 1990s not to correlate with BMR, when fat-free body mass was adjusted for. New research has, however, come to light that suggests anaerobic exercise does increase resting energy consumption (see “Aerobic vs. anaerobic exercise“). Illness, previously consumed food and beverages, environmental temperature, and stress levels can affect one’s overall energy expenditure as well as one’s BMR.

 

Indirect calorimetry laboratory with canopy hood (dilution technique)

BMR is measured under very restrictive circumstances when a person is awake. An accurate BMR measurement requires that the person’s sympathetic nervous system not be stimulated, a condition which requires complete rest. A more common and closely related measurement, used under less strict conditions, is resting metabolic rate (RMR).

BMR and RMR are measured by gas analysis through either direct or indirect calorimetry, though a rough estimation can be acquired through an equation using age, sex, height, and weight. Studies of energy metabolism using both methods provide convincing evidence for the validity of the respiratory quotient (R.Q.), which measures the inherent composition and utilization of carbohydrates, fats and proteins as they are converted to energy substrate units that can be used by the body as energy.

 

c)     Method of indirect calorimetry with the incomplete gas analyses

 

It is difficult to measure all of the end products, but measurement of O₂ consumption is relatively easy. Since O₂ is not stored and since its consumption, except when an O₂ debt is being incurred or repaid, always keeps pace with immediate needs, the amount of O₂ consumed per unit of time is proportionate to the energy liberated. Method of indirect calorimetry with the incomplete gas analyses includes determining only the quantity of oxygen consumed per unit of time from spirograph. Then we may calculate the quantity of daily O₂ consuming and value metabolic processes.).

State of metabolic processes (The amount of energy liberated by the catabolism of food in the body is the same as the amount liberated when food is burned outside the body. The amount of energy liberated per unit of time is the metabolic rate.)

a) Definition of the basal metabolic rate (In order to make possible a compareson of the metabolic rates of different individuals and different species, metabolic rates are usually determined at as complete mental and physical rest as possible, in a room at a comfortable temperature, 12-14 hours after the last meal. The metabolic rate determined under these conditions is called the basal metabolic rate.)

Both basal metabolic rate and resting metabolic rate are usually expressed in terms of daily rates of energy expenditure. The early work of the scientists J. Arthur Harris and Francis G. Benedict showed that approximate values could be derived using body surface area (computed from height and weight), age, and sex, along with the oxygen and carbon dioxide measures taken from calorimetry. Studies also showed that by eliminating the sex differences that occur with the accumulation of adipose tissue by expressing metabolic rate per unit of “fat-free” or lean body mass, the values between sexes for basal metabolism are essentially the same. Exercise physiology textbooks have tables to show the conversion of height and body surface area as they relate to weight and basal metabolic values.

The primary organ responsible for regulating metabolism is the hypothalamus. The hypothalamus is located on the diencephalon and forms the floor and part of the lateral walls of the third ventricle of the cerebrum. The chief functions of the hypothalamus are:

control and integration of activities of the autonomic nervous system (ANS)

The ANS regulates contraction of smooth muscle and cardiac muscle, along with secretions of many endocrine organs such as the thyroid gland (associated with many metabolic disorders).

Through the ANS, the hypothalamus is the main regulator of visceral activities, such as heart rate, movement of food through the gastrointestinal tract, and contraction of the urinary bladder.

production and regulation of feelings of rage and aggression

regulation of body temperature

regulation of food intake, through two centers:

The feeding center or hunger center is responsible for the sensations that cause us to seek food. When sufficient food or substrates have been received and leptin is high, then the satiety center is stimulated and sends impulses that inhibit the feeding center. When insufficient food is present in the stomach and ghrelin levels are high, receptors in the hypothalamus initiate the sense of hunger.

The thirst center operates similarly when certain cells in the hypothalamus are stimulated by the rising osmotic pressure of the extracellular fluid. If thirst is satisfied, osmotic pressure decreases.

All of these functions taken together form a survival mechanism that causes us to sustain the body processes that BMR and RMR measure.

Causes of individual differences in BMR

The basal metabolic rate varies between individuals. One study of 150 adults representative of the population in Scotland reported basal metabolic rates from as low as 1027 kcal per day (4301 kJ/day) to as high as 2499 kcal/day (10455 kJ/day); with a mean BMR of 1500 kcal/day (6279 kJ/day). Statistically, the researchers calculated that 62.3% of this variation was explained by differences in fat free mass. Other factors explaining the variation included fat mass (6.7%), age (1.7%), and experimental error including within-subject difference (2%). The rest of the variation (26.7%) was unexplained. This remaining difference was not explained by sex nor by differing tissue sized of highly energetic organs such as the brain.

Thus there are differences in BMR even when comparing two subjects with the same lean body mass. The top 5% of people are metabolizing energy 28-32% faster than individuals with the lowest 5% BMR. For instance, one study reported an extreme case where two individuals with the same lean body mass of 43 kg had BMRs of 1075 kcal/day (4.5 MJ/day) and 1790 kcal/day (7.5 MJ/day). This difference of 715 kcal/day (67%) is equivalent to one of the individuals completing a 10 kilometer run every day.

 

b) Factors which influence on basal metabolic rate (Intensity of metabolic processes depend on muscular exertion, recent ingestion of food, high or low environmental temperature, height, weight, and surface area, sex, age, emotional state, climate, body temperature, pregnancy or menstruation, circulating level of thyroid hormones, circulating epinephrine and norepinephrine levels, condition of inner organs. In females, the basal metabolic rate at all ages is slightly lower than in males. The rate is high in children and declines with age. Apathetic, depressive persons may have low basal metabolic rate.).

c) Specific dynamic action of food (SDAF)

Recently ingested foods also increase the metabolic rate because of their specific dynamic action. The specific dynamic action of a food is the obligatory energy expenditure that occurs during its assimilation into the body. An amount of protein sufficient to provide 100 kcal increases the metabolic rate a total of 30 kcal; a similar amount of carbohydrate increase it 6 kcal; a similar amount of fat increase it 4 kcal. This means that the amount of calories available from 3 foods is in effect reduced by this amount; the energy used in their assimilation must come from the food itself or the body energy stores.

Energetic expenditure in the different functional activity

a) Characteristic of I professional group

These are the person, whose work do not connect with the spend on physical work or do not need essential physical effort. Common daily expenditure of energy is 2200-3300 kcal..

b) Characteristic of II professional group

Worker of mechanical work and sphere of service, which work does not need a big physical effort. Common daily expenditure of energy is 2350-3500 kcal..

c) Characteristic of III professional group

Worker of mechanical work and sphere of service, which work connects with the considerable physical efforts. Common daily expenditure of energy is 2500-3700 kcal..

d) Characteristic of IV professional group

Worker of do not mechanical work or partly mechanical work with a big and middle heavility. Common daily expenditure of energy is 2900-4200 kcal.

e) Characteristic of V professional group

Worker of do not mechanical work with a big heavility. Common daily expenditure of energy is more than 4200 kcal.

Calculation of metabolism by the method of indirect calorimetry with the incomplete gas analyses

 

The usage of the oxygen we can count on the rejection of the spirogramm from the basic level for a minute. While the oxygen is absorbed from the breathing bag of spirograph and the spirogramm goes up (compensation of the oxygen is not needed because the carbon dyoxyde that breathes out connects with some chemical substance). Distance AB shows the amount of oxygen that is absorbed by the organism of the human being for minute. If you want to determine the amount of minute absorption of oxygen, you have to multiply the rejection of notation on 20. Normally for one minute is 200-300 ml of oxygen.

 

Estimination of normal amounts of basal metabolism

Studying the normal weight and high with the help of first table we can find out general surface of the body. Then, taking into consideration sex and age (table 2), we can find the standard of basic exchange on 1 m² body’s surface per hour.

Normal amounts of basic exchange in this case will be equal to multiply of founded quantities, uncounted on 24 hours.

 

Table. Standard of basic exchange

 

 

characteristic of physiological value of maiutritive products

a) Milk and sour milk products

Milk is one of the most valuable products of feed. It has all necessary substances for normal growth and development of organism. Milk has near 100 different components, and near 20 amino acids. Milk fat has a lot of high insatiable fat acids, vitamins. It is in emulsification case. Milk has cholesterol and lecetin, which are in good balance condition. In milk present milk sugar – lactose, which help mastering of calcium. Milk has different mineral substances, the optimal concentration of calcium and phosphorus. In milk present vitamins A, D, B₂, B₆. Sour milk products are cream, sour cream, cheese, yoghurt. It is mastering better than milk (after one hour mastering 91 % of sour milk products and only 32 % of milk.

Meat and meat products

In food use meet of cattle, live-stock, pigs, rabbits, birds, meat products. It is the main source of proteins, it has fats, extractive and mineral substances, vitamins. Boiled meat has a better effect on digestive organs than grilled and stew. Veal, beef, rabbit, chicken, turkey digestive better than meat from pig, goose, duck.

 

 Grain products (grain, bread)

Cereals make from grain-crops. It has a lot of carbohydrates, some quantity of proteins, and small quantity of fats. Cereals has phosphor and calcium, iron, magnesium, vitamins of B group.

 

There are rise, oats, millet, buckwheat, barley cereals. Bread has 40-50 % of carbohydrates, 5-8 % of protein. In bread are present proteins. Brown bread has more influence on stomach secretion than white bread; fresh bread has more influence on stomach secretion than stale bread and piece of dried bread.

 Vegetables, fruits and small fruits (berries)

Vegetables is the main source of carbohydrates in a case of sugar, starch, pectin. In carrot is present near 6 % of carbohydrates, in beetroot present near 8 % of carbohydrates. There is 75-95 % of water in vegetables. Vitamins and mineral substances are present in a big quantity in vegetables too. Vegetables stimulated stomach secretion, motor function of digestive tract, production of bile. It is help to mastering proteins, fats, carbohydrates and vitamins. Fruits and small fruits (berries) have a lot of vitamins, mineral salts. There are near 85 % of water in fruits and small fruits (berries). It has organic substances, pectin.

 

Acquiring of food

Mastering of food is a ratio between quantity of nutrition which are master by organism to common quantity of food which we eat. Near 95 % of animal products are mastering, near 80 % of plant products are mastering, near 82-90 % of mix products are mastering. Mastering of protein from animal products is 97 %, from plant is 85 %, and from mix food is 92 %. Food must be good chew; it must be good surrounding condition for eating.

 Isodynamic of nutritious substances, their caloric coefficient

We eat protein, carbohydrates, fats. Products of it hydrolyzing go into energy of organism. Amino acids, fat acids, monosaccharides connect in energy metabolism. It all has own energy value. Caloric coefficient of fat is 9,0 kcal/g, protein is 4,0 kcal/g, carbohydrates is 3,75 kcal/g. But we must remember, that we must eat fats, protein, carbohydrates, because in this case, when we eat only one products, may be only energy substitution and our organism need all nutrition for vital activity.

Principles of putting of nutritive rations

a) Accordance of calorific value of day ration to energy loss

Caloricity of daily ration must be equal to energy spend of organism. Person of I professional group need 40 kcal/kg of weight; person of II professional group need 43 kcal/kg of weight; person of III professional group need 46 kcal/kg of weight; person of IV professional group need 53 kcal/kg of weight; person of V professional group need 61 kcal/kg of weight.

b) Regime of nutrition

If we eat 4 times per day: breakfast must have 25-30 % of daily caloricity, lunch (after dinner eating) or before supper eating must have 10-15 %, dinner must have 40-45 % daily caloricity, supper must have 20 % of daily caloricity. If we eat 3 times per day: breakfast must have 30 % of daily caloricity, dinner must have 45-50 % daily caloricity, and supper must have 20-25 % of daily caloricity. Time between breakfast and dinner must be to 5-6 hours; time between dinner and supper must be 6-7 hours. Optimal duration between eating is 4-5 hours, at night is 8-10 hours.

c) Completeness and coordinateness of ration

Our food must have optimal ratio of protein, fats, carbohydrates, vitamins, mineral substances. Optimal norm of protein is 1,5 g/kg of weigh per day. Protein must give 14-15 % of daily caloricity. Optimal norm of fat is 1,5 g/kg of weigh per day. Fat must give 28-30 % of daily caloricity. Average norm of carbohydrates is 400-500 gram per day. They provide 50-60 % of daily caloricity. Ratio of protein : fat : carbohydrates is 1 : 0,8 : 3 or 1 : 1 : 4 for peoples, which has high mental activity; 1 : 1 : 5 for peoples with physical activity.

 

 

d) Individual-physiologic peculiarities of organism into consideration Breakfast must begin from salad, which activate digestive secretion. Then must be food with the main source of energy and nutrition’s, on the end must be tonic drink (tea, coffee, cacao). Dinner must begin from salad (when you have less of appetite). We must remember than dinner does not begin from food, which decrease stomach secretion. Supper must consist food which good digest (fish, milk, and eggs), drinks, which do not stimulate central nerve system.

 

State the value of metabolism

1. With the food was eat 98 g of protein. With the urine was excreted 12 g of nitrogen, with the sweat – 0,5 g. How many protein was break up in the organism?

2. How many proteins was break up in the organism when we know that with the urine was excreted 13,1 g of nitrogen?

3. With the urine was excreted 14,2 g of nitrogen. How many proteins was break up in the organism?

4. With the food was eat 100 g of protein, with the urine was excreted 8 g of nitrogen. State the value of nitrogen balance.

5. With the food was eat 50 g of protein, with the urine was excreted 12 g of nitrogen. What is the nitrogen balance?

6. With the food person was eat 85 g of protein. With the urine was excreted 10 g of nitrogen, with the sweat – 0,25 g. State the value of nitrogen balance.

7. How many proteins was break up in the organism when we know that with the urine was excreted 12,7 g of nitrogen?

8. In mans organism with the weight of 80 kg index of “wear” in the rest position is 0,035 g/kg/day. How many protein he spend per day? What hormons are regulates intensity of protein metabolism?

9. To define the day spending of protein in the rest position in the human with weight of 70 kg, if you know that index of “wear” is 0,05 g of nitrogen per 1 kg of weight per day.

10. The man of mental work with the food eat 120 g of plants origin protein only. Is there the protein short-coming?

11. Thirteen-year boy with the food was eat 75 g of protein, 75-year man –54 g. With the urine was excreted 7 g of nitrogen in boy, 12 g of nitrogen in the old man. To compare the nitrogen balance and explain the cause of this condition.

 

Creating the food allowance

During the lesson student should get an individual task from the teacher to create the food allowance, which should be given as a table:

 

Nutrition regime and appropriate energetic value of food taking (kcal)	Name of the dishes and products	Chemical structure and energetic value of the products						Actual calorie content of the food (kcal)
		protein		carbohyd-rates		fats
		gram	kcal	gram	kcal	gram	kcal
Breakfast
Lunch
Dinner
Supper
Total per day

 

References:

1. Review of Medical Physiology // W.F.Ganong. – 24th edition, 2012.

2. Textbook of Medical Physiology // A.C.Guyton, J.E.Hall. – Eleventh edition, 2005.

3. The human organs by Russell Myles DeCoursey, Mc Graw-Hill book company. – New York and etc., Editor 3^th .