Metabolism PDF

Cell METABOLISM  The term metabolism refers to all of the biochemical reactions by which complex molecules taken into an organism are broken down to produce energy. Energy is used to build up new compounds.  All metabolic reactions fall into one of two gen...

Cell METABOLISM  The term metabolism refers to all of the biochemical reactions by which complex molecules taken into an organism are broken down to produce energy. Energy is used to build up new compounds.  All metabolic reactions fall into one of two general categories: Catabolic Reactions Anabolic Reactions  1- Catabolism It is a metabolic process occurring in living cells by which complex molecules are broken down to produce small and usable amount of energy to sustain life. Releasing energy is exergonic process.  Catabolic pathway is the type of a metabolic pathway in which oxidative breakdown of larger complex molecules generates a huge amount of energy. Releasing energy is exergonic process.  2- Anabolism It is a metabolic process wherby energy is consumed to synthesize amino group substances acids transformation into protein. Anabolism is the building-up aspect of metabolism. Processes of catabolism and anabolism  ATP & Metabolism  The amount of free energy in the third and second phosphate of high energy bonds /mole of ATP is 8000 cal. under standard condition.  Released and Reform Energy Released Energy ATP – 8000 cal ADP – 8000 cal AMP Reform Energy ATP + 8000 cal ADP + 8000 cal AMP + PO4 + PO4  Synthesis Of ATP ATP is manufactured in the mitochondria during aerobic respiration process. So, mitochondria are also called the powerhouses of the cell.  Basal Metabolic Rate (BMR) It is the mimimal caloric requirement needed to sustain life in a resting state i.e. amount of energy of body would burn if you slept all day (24 hours). Physiological Factors That Affect BMR Age: In youth, BMR is higher, age slows BMR. Height: Tall, thin people have higher BMR. Growth: Children and pregnant have higher BMR. Body composition: The more lean tissue, the higher BMR, more fat tissue, the lower BMR.  Fever: Fever can rise BMR. Stress: Stress hormone can rise the BMR. Envivonmental temperture: Both the heat and cold raise BMR. Fasting / starvation : Fasting /Starvation lower BMR. Malnutrition: It lowers the BMR. Thyroxin: The thyriod hormone is key BMR regulator, more thyroxin, the higher BMR. Sympathetic stimulation: Liberation of norepinephrine and epinephrine increase the metabolic rate. These hormones directly affect cells to cause glycogenolysis.  Calculation of BMR Either by: General calculation or Harris-Benedict calculation  1- General Calculation BMR=Body weight in lbs x10 kcal/lb Ex.Ahmed weighs 150 lbs. BMR = 150 x 10 kcal/lb = 1500 kcals.  2- The Harris-Benedict Equation: Males: 66+(13.7x W) + (5 x H) - (6.8 x A) Females: 655+ (9.6 x W)+(1.7 x H) - (4.7 x A) W = weight in kg (weight in lb/2.2 lb/ kg. H = height in cm (height in inches x 2.54 cm/in). A = age in years. Ex. Ahmed weighs 150 lbs, stands 56”, and is 21 years old. 150lbs/2.2lb/kg = 68kg. and stands is 56''=56 inches x 2.54 cm=168cm BMR=66+(13.7x 68)+ (5x 168)–(6.8 x 21) BMR = 66 + 932 + 840 - 143 = 1695 kcals/day.  Energy Expenditure Energy expenditure shows approximate energy during performance at various physical activities. i.e. how many hours you spent walkings, standing, running, exercising, sleeping and so on.  For example: Let’s say that Ali spent 10 hours sitting, 3 hours walking, 1 hrs standing, 3 hrs studying, 1 hrs of running at 7.5mph, and 6 hrs of sleeping. This is Hassan’s activty record for that day. Now we can use the following charts to calculate how much energy burned per day.  charts 1.1Kcals/minute burned during sleep i.e 1.1 ×360 minutes (6 hours) = 369 kcals. 1.7 kcals /minute burned during studying i.e 1.7× 130 minute (3 hours) = 306 Kcals. 2.5 kcals /mintues burned during walking at 3.5 mph i.e. 2.5× 180 (3 hours) = 936 Kcals. 14.1 Kcals/minutes burned during running at 7.5 mph i.e. 14.1 × 60 (1 hour) = 846 Kcals. 2.5 /kcals /mintues burned during standing i.e. 2.5× 60 (1 hours) = 150 Kcals. 1.5 kcals /mintues burned during sitting i.e. 1.5× 60 minute (10 hours) = 900 Kcals.  Energy expenditure = 396 + 306 + 936 + 846 + 150 + 900 = 3534 Kcals during this day. Ali needs to consume this much in his diet to maintain his body weight. If he wanted to gain weight, he would have to eat more. If he wanted to lose weight, he would have to expend more energy with exercise and partially cut his food intake.  Carbohydrate Metabolism Carbohydrate catabolism is the breakdown of carbohydrates into monosaccharide. Monosaccharide (glucose, fructose and galactose) are absorbed through portal vein into liver and carried to the cells of the body by circulation.  Phosphorylation of Monosaccharides Glucose +ATP Glucokinase Glucose -6-P Fructose +ATP Fructokinase Fructose -6- P Galactose +ATP Galactokinase Galactose -6-P  The phosphorylation of monosaccharides is completely irreversible except  Except in liver cells, renal tublar and intestinal cells, in which specific phosphatases are available for reversing manner.  Glycolysis Glycolysis is the process in which glucose is broken down to produce energy. It produces two molecules of pyruvate, ATP, NADH and water. The process takes place in the cytoplasm of a cell and does not require oxygen. It occurs in both aerobic and anaerobic organisms. Glycolysis  By complete catabolism of one molecule of glucose by glycolysis and TCA cycle, 36 molecules of adenosine triphosphate (ATP) are formed.  Glycogenesis It is the process of glycogen formation. Lactic acid, glycerol, pyruvic acid and some deaminated amino acid can converted into glucose and thereby into glycogen.  Glycogenolysis It is the process of glycogen breakdown. Glycogenolysis does not occure by reversal chemical reactions as that manner to form glycogen, but each glucose molecule on branch of glycogen is split away by phosphorylase enzyme i.e. several enzymes split glycogen.  Gluconeogenesis Glucose can be formed from amino acids and from glycerol portion of fat.  (A) Aerobic Glycolysis Aerobic glycolysis of glucose to pyruvate, requires 2 ATP to activate the process, with the production of 4 ATP and 2 NADH. The 2 Pyruvic Acid are converted into 2 Acetyl CoA.  By complete catabolism of one molecule of glucose by glycolysis and TCA cycle, 36 molecules of adenosine triphosphate (ATP) are formed. Tricarboxylic acid (TCA) cycle is an aerobic oxidative metabolism whereas glycolysis is anaerobic oxidative metabolism.  (B) Anaerobic Glycolysis On, oxygen become insufficient, cellular oxidation connot take palce. The glycolytic breakdown of glucose to pyruvic acid do not require oxygen. Pyruvic acid does not enter the Kreb's cycle but is reduced to lactic acid producing little energy as following: Glucose +2ATP anaerobically 2Lactic acid+4ATP  Lactic Acid Cycle ( Cori Cycle ) It is pathway by which muscle lactate contributes to blood glucose. Lactate formed in muscle by glycolysis is transported to the liver and resynthesized to glucose there. Glycogen Glycogen Cori Cycle  Lipid Metabolism There are three families of lipids: (1) fats (“triglyceride”). (2) phospholipids, These are major components of the plasma membrane. (3) steroids are synthesized in the adrenal cortex, the gonads, and the placenta.  Neutral Fat ( Triglyceride ) They are used in the body mainly to provide energy for different metabolic processes. Triglyceride is formed of three long chain fatty acids bound with one molecule of glycerol: Triglyceride Glycerol + 3Fatty A.  Fat Depots Fats or triglycerides are stored in two major tissues of the body, the adipose tissue and liver and used for energy. Fat cells can also synthesize fatty acids and triglycerides from carbohydrates.  Triglycerides and Energy The first stage of triglyceride utilization for energy is hydrolysis of triglyceride into fatty acids and glycerol. Both products of hydrolysis are transported to the active tissues where they are oxidized to give energy. Almost all cells with except of brain tissue can use fatty acids for energy.  Oxidation of Glycerol Glycerol is converted to α - glycerol phosphate by glycerophosphokinase Glycerol glycerophosphokinase α-glycerol-P ATP ADP  By NAD- dependent enzyme α -glycerol phosphate dihydroxy acetone- P Dihydroxy acetone phosphate enters glycolysis to be reduced by enzyme to lactate under anaerobic conditions (1ATP) or to CO2 and H2O under aerobic condition (19 ATP).  Oxidation of Fatty acids The degradation and oxidation of fatty acids occur only in the mitochondria. The entrance of fatty acid into mitochondria catalyzed by carnitine enzyme as a carrier substance. Inside mitochondria, the fatty acid splits away from carnitine and is then oxidized degraded into Acetyl CoA fragments.  Complete oxidation of one palmitate molecule (fatty acid containing 16 carbons) generates 129 ATP molecules. Protein Metabolism  Transamination The removal of the amino groups of amino acids begins with the transfer of amino groups to just one amino acid - glutamic acid (or glutamate ion). This is catalysed by transaminase enzymes which transfer the amino group from amino acids to alpha- ketoglutarate. The product is an alpha-keto acid formed from the amino acid and glutamate (formed from the addition of the amino group to alpha- ketoglutarate. transaminase enzyme  Transamination is one of the major degradation pathways which convert essential amino acids to non- essential amino acids (amino acids that can be synthesized de novo by the organism).  Deamination Most of our nitrogenous waste comes from the breakdown of amino acids. This occurs by deamination. Deamination of amino acids results in the production of ammonia (NH3).  Urea Formation Urea is the chief nitrogenous waste of mammals. Ammonia is an extremely toxic base and its accumulation in the body would quickly be fatal. However, the liver contains a system of carrier molecules and enzymes which quickly converts the ammonia (and carbon dioxide) into urea.  One Turn Of Cycle Consumes 2 molecules of ammonia Consumes 1 molecule of carbon dioxide Creates 1 molecule of urea (NH2)2CO Regenerates a molecule of ornithine for another turn. Although our bodies cannot tolerate high concentrations of urea but, it is much less poisonous than ammonia. Urea is removed efficiently by the kidneys.  Ornithine transcarbamylase enzyme Metabolism & Hormones  1- Growth Hormone Stimulates protein synthesis and strength of bone. Release of growth hormone from the pituitary gland in the brain is increased with increasing aerobic exercise time.  2- Endorphins An endogenous opioid from the pituitary gland that blocks pain, decreases appetite, creates a feeling of euphoria and reduces tension and anxiety. Endorphins that are produced from exercise tend to stay in your blood for a longer period of time. This makes longer duration exercise easier (you’re feeling no pain).  3- Testosterone An important hormone in both males and females for maintaining muscle tone/volume/strength, increasing basal metabolic rate (metabolism), decreasing body fat, and feeling self-confident. It’s produced by the ovaries in females and by the testes in males. Females have only about one tenth the amount of testosterone that males do, but even at that level in females it also plays a role in libido and intensity of orgasms.  4- Estrogen The most biologically active estrogen, 17 beta estradiol, increases fat breakdown from body fat stores so that it can be used and fuel, increases basal metabolic rate (metabolism), elevates your mood, and increases libido. The amount of 17 beta estradiol secreted by the ovaries increases with exercise, and blood levels may remain elevated for one to four hours after exercise.  5- Thyroxine A hormone produced by the thyroid gland, Thyroxine raises the metabolic rate of almost all cells in the body. This increase in “metabolism” helps you to feel more energetic and also causes you to expend more calories, and thus is important in weight loss. Blood levels of thyroxine increase during exercise.  6- Epinephrine A hormone produced primarily by the adrenal medulla that increases the amount of blood the heart pumps and directs blood flow to where it’s needed. Stimulates breakdown of glycogen (stored carbohydrate) in the active muscles and liver to use as fuel. It also stimulates the breakdown of fat (in stored fat and in active muscles) to use as fuel. The amount of epinephrine released from the adrenal medulla is proportional to the intensity and duration of exercise.  7- Insulin An important hormone in regulating (decreasing) blood levels of glucose and in directing glucose, fatty acids, and amino acids into the cells. Insulin secretion is increased in response to a rise in blood sugar. Blood levels of insulin begin to decrease about 10 minutes into an aerobic exercise session and continue to decrease through about 70 minutes of exercise.  8- Glucagon It is secreted by the pancreas, It raises blood levels of glucose. It causes stored carbohydrate (glycogen) in the liver to be released into the blood stream to raise blood sugar to a normal level. It also causes the breakdown of ( used as fuel ). Glucagon typically begins to be secreted beyond 30 minutes of exercise when blood glucose levels may begin to decrease.