METABOLISM AND FACTORS AFFECTING METABOLIC RATE CONCEPT OF METABOLISM

                     

METABOLISM AND FACTORS AFFECTING METABOLIC RATE

CONCEPT OF METABOLISM- Metabolism is a term that is used to describe all chemical reactions involved in maintaining the living state of the cells and organism.

It is commonly used to specifically to the breakdown  of food and its transportation into energy. Metabolism can  be conveniently be divided into categories, which are;

(1)                    Catabolism – The breakdown  of molecules to obtain energy.

(2)                    Anabolism – The synthesis of all compound needed by the cells.

Metabolism  is closely linked to nutrition and the availability of nutrient.

NUTRITION , METABOLISM AND ENERGY

Nutrition is the key to metabolism. The pathway of metabolism rely upon nutrients that they breakdown in order  to produce energy. This energy in turn is required by the body to synthesize new protein, nucleic acids ( DNA AND RNA ) e.t.c

Essential nutrient  supply energy and supply the necessary chemicals which the body itself cannot synthesize. The diet need essential nutrient like carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, and around 20 other inorganic element. The major elements are supplied in carbohydrates, lipids and protein. In addition, vitamins, minerals and water are necessary.

CARBOHDRATES IN METABOLISM

Foods supply carbohydrates in three forms; sugar, starch and cellulose ( fibres ). Starches and sugar form major and essential source energy for humans. Fibres contribute to bulk in diet. Body tissues depend on glucose for all activities, carbohydrate and sugar yield glucose by digestion or metabolism.

 PROTEIN METABOLISM

Protein are the main tissue builders in the body. They are part of every cell the body. It help in cell structure, fuctions, haemoglobin formation to carry oxygen, enzymes to carry out vital reactions and a myriad of other functions in the body. Proteins are vital in supplying nitrogen for dna and rna genetic material and energy production.

Proteins are necessary for nutrition because they contain amino acid, the human body is unable to synthesize and these are called essential amino acids. The essential amino acids include;

(i)            Lysine

(ii)        Tryptophan

(iii)     Methionine

(iv)     Leucine

(v)         Isoleucine

(vi)     Isoleucine

(vii)  Phenylalanine

(viii)                                                                                     Valine

(ix)     Threonine

FATS IN METABOLISM

Fats are concentrated sources of energy. They produce twice as much energy as either carbohydrates of protein on a weight basis. The function of fats include;

(i)            Providing a reserve storage for energy.

(ii)        Helpd to absorb fat soluble vitamins

(iii)     Helping to form the cellular structure

(iv)     Forming a protective cushion and insulation around vital organs.

Essential fatty acid include unsaturated fatty acid like linole, linolinic  and arachidonic acids. These need to be taken in our diet. Saturated fats along with cholesterol have been implicated in arteriosclerosis and heart disease.

MINERALS AND VITAMINS IN METABOLISM

The minerals in foods do not contribute directy to energy but are important as body regulators and play a role in metabolic pathway of the body . important minerals includes calcium, iron, sodium, potassium, copper, zinc, fluorine, magnesium e.t.c

Vitamins are essential organic compounds that the human body cannot synthesize by itself and must therefore be present in the diet.

Vitamins particularly important in metabolism include; vitamin a, niacin or nicotinic acidl pantothenic acid etc

METABOLISM PATHWAYS

The chemical reactions of metabolism are organized into metabolic pathways. These allow the basic chemicals from nutrition to be transformed through  a series of steps into another chemical by a sequence of enzymes.

Enzymes are crucial to metabolism because they allow organism to derive desirable reaction that require energy. These reactions also ar coupled with those that release energy. As enzymes act as catalysts they allow these reaction to proceed quickly and efficiently.

METABOLISM CONTROL

The metabolic pathways are complex and interdependent with the changing enviroments , the reaction of metabolism must be finely regulated to maintain a constand set of conditions with cells , a condition called homeostasis . control of metabolic pathways also allow organism to respond to signal interact actively with their environment.

CONCEPT OF CONTROL AND REGULATION

Regulation of metabolic pathways includes regulation of an enzyme in a pathway by increasing or decreasing its response to signal. Control involves monitoring the effect that these changes in an enzymes activity have on the overall rate of the pathway for example, an enzyme may show large changes in activity being highly regulated but if these changes have little effect on the flux of a metabolic pathway then this enzyme is not involved in the control the pathway.

REGULATION OF CARBOHYDRATE METABOLISM

Glucose homeostasis is a complicated interaction of metabolic pathway. It is vital for living organism. These process either increase or derease the blood glucose concentration but the work together  in order to maintain an optimal level. Glucose is derived from carbohydrate taken in the diet. Rising level of glucose is the blood stimulate the releaseof insulin from the cells of the islets of Langerhans in the pancreas.

Insulin is the only hormone that reduces  blood glucose levels and it dose this by activating the glucose transport mechanism and glucose utilizing metabolic pathway in different tissues of the body. Thus insulin down regulate glucose forming pathways.

Insulin stimulates;

(i)            Uptake of glucose by muscle and adipose tissue

(ii)        Glycogenesis (formation of glycogen from free glucose )

(iii)     Protein

Disturbed glucose homostasis is vital in causation of diseases like diabetes.

LIBERATIONN OF ENERGY THROUGH INTERNAL RESPIRATION

Liberation of energy through cellular or internal respiration occurs in two main stages involving series of chemical reaction and respiratory enzymes.

The first stage of internal respiration – glycolysis- takes place anaerobically. Glucose molecule is first phosphorylated by the adition of a phosphate group to become glucose phosphate. Through series oxidative enzymes, the glucose phosphate is converted to two molecules of triose sugar, this triose sugar is then converted to pyrvic acid by the removal of four atoms of hydrogen the co-enzyme called nicotinamide adenine dinucleotide ( NAD) with the formation of two ATP.

The second stage of internal respiration takes place aerobically aerobically in the mitochondria, if sufficient oxygen is available each molecule of pyruvic acid is oxidized to remove one molecule of carbon dioxide ( decarboxylation ) and two atoms of hydrogen (dehydrogenation) forming cne molecule of acetic acid, a two carbon sugar.  Carbon dioxide  is released.

KREPS’ CIRCLE  OR CITRIC ACID CIRCLE

The acetic acid enters into a krebs (krebs circle) where it is joined to a four carbon acid ( oxaloacetic acid) present in the mitochondria to form citric acid ( a six carbon acid )

One molecule of carbon atom in the form of carbon dioxide and one atom of hydrogen is removed by oxidative decarboxylation and nicotinamide adenine dinucleotide to one molecule of ketoglutaric acid ( a 5 carbon sugar ). Another molecule of carbon dioxide and one atom of hydrogen is removed from ketoglutaric acid to per a 4-carbon succinic acid .One atom of hydrogen is removed from succinic acid to form a four malic acid. Again another hydrogen atom is removed from malic acid to form a 4-carbon oxaloactic acid. The oxaloactic acid then combines with the acetic acid again with the circle is repeated. The hydrogen atom is removed in successive stages combine with molecular oxygen to form water. The overall reaction of glycolysis and krebs' cycle gives 38 ATP.

FACTORS AFFECTING METABOLISM

1. Muscle  mass:  the amount of muscle tissue  on one’s body greatly affects the rate of metabolism, the more the muscle tissue a body possesses the more the  energy to sustain it, resulting in higher metabolic rate and vise versa.

2.  Age: as ones ages the body looses muscle and several hormonal changes in the system leading to low metabolism, during the early stage of life, there are higher rate of metabolism to ensure growth and developmet.

3. Gender : the gender of an individual also determines the rate of metabolism,  males tend to have higher metabolic rate than female individuals.

4. Genetics : genetics of an individual also determines also determines the rate of metabolic, tabnormal genetic make up of an individual can make the metabolic of an individual to be too slow or too fast.

5. Physical activity: physical activity of an individual  affect his/her metabolic rate. Physical activity increases the rate of metabolism and vise versa.

6. Health: the health of an individual determines the metabolic rate of an individual, generally ill health slows down metabolic rate while good health ensures optimum metabolic rate.

7. Drugs : use of certain drugs affect the rate of metabolism. The use of caffine and nicotine can increase metabolic rate, so also do anti-depressant drug decrease metabolic rate.

8. Diet: the type of diet which an individual takes also affects his/her metabolic rate to a great a extent. Diet rich in carbohydrate and fat provide material for higher metabolism and vise- versa.