An Increase in the Requirement of Nutrients - Assignment Example

Answers to questions a. Malnutrition is a of health that arises due to an insufficient calorie intake causing under nutrition or due to insufficient intake of one or more of the essential nutrients like proteins resulting in deficiency. The above two are the primary causes that can lead to Marasmus and Kwashiorkor respectively. The other secondary causes include inadequate absorption or utilization of essential nutrients (malabsorption syndrome) or an increase in the requirement of nutrients due to destruction or excretion that occur secondary in case of diseases. b. Proteins are generally required for growth and maintenance of body weight in humans and they are made up of a simple chemical substance called amino acids, which in turn can be classified as essential and non-essential amino acids. Essential amino acids are those that can only be derived from the diet and non-essential are those that can be synthesized in the body. The essential amino acids contents differ from one protein to another. Hence the nutritional value of dietary foods proteins depends on their essential amino acid content. All protein rich foods like milk, eggs, cereals, fish etc may be rich in only in certain essential amino acids. Hence in order to gain all the essential amino acids a balanced diet of the proteins foods is needed. In case of vegetarians a balanced use of all the cereals is required to gain all the essential amino acids. If any cereal is eliminated in particular it might result in a deficient supply of the essential amino acids present in it, thereby leading to protein deficiency. c. Milk and cereals are generally consumed by vegetarians in their daily diet which are good sources of proteins. 2. a. i) The brain requires a readily available form of sugar and starch would provide the readily required glucose. The mean protein requirement is about 70 g/ day for an adult. The amount of cellulosic fibers required is about 40 g. these are indigestible polysaccharides which do not actually supple calories but they help by delaying the passage of food through the GI tract, stimulate intestinal peristalsis and help prevent constipation. The saturated fat consumption could be lesser when compared to the unsaturated fat content as the dietary fat intake should ideally not be more then 80 g/day. The calcium intake is ideal. ii) Fat content in the diet should generally be less especially in case of sedentary and obese people. An increase in fat content, especially saturated fat, may lead to an increase in serum cholesterol levels and thereby fat deposition in arteries resulting in atherosclerotic conditions. The type of fat taken in the diet should also be considered. Unsaturated fat and triglycerols have better digestibility and these are also better absorbed by the human intestinal tract. A good amount of essential fatty acids should also be taken which help reduce the cholesterol levels in the blood. b. i) Starch is an easily digestible macromolecule and these contribute to the major calories burnt. About 60% of total calories come from starches. These on digestion gives rise to simple sugars like glucose which is a major source of energy to the brain. The simple sugars got from starch digestion are generally not present in the feces as they are effectively absorbed. On the other hand dietary fiber, mainly obtained from plant-material, contributes to the bulk of the stool as they are less effectively digested and thereby act as a vehicle for fecal water and increase fecal bacterial volume. Cellulose is one such less fermentable dietary fiber. The digestion of fiber takes place in the colon by bacteria and the extent if digestion depends on the physical and chemical nature of the fiber. In general the fiber constituents of fruits and vegetables are more easily digestible than those fibers that are contained in bran’s and such food stuffs. Cellulose is not digested by the human colonic bacteria. The average stool weight in populations that consume a fiber rich diet is about 300g. ii. Cellulose like polysaccharides contributes to the bulk of the stool. They do not contribute any calories but are required for normal digestion and excretion process. The hydration capacity of such fibers also causes an induction of bacterial growth. Its use in cases of constipation and diverticular diseases is well established as it increases the frequency and urgency of defecation and also decreases colonic pressure. By shortening the transit time it has also been proposed that fiber protects against cancer of the colon. And ingestion of a fiber rich diet causes a decrease in secondary bile acids in stools. In addition they also lower plasma cholesterol levels that ay result in lower incidence of atherosclerotic heart diseases. c. Intake of Vitamin D will improve the efficiency of Calcium intake. 3. a. Vitamins are organic nutrients that are required in small quantities for many different biochemical functions. These accessory factors are found in natural products and are generally not synthesized in the body. A constant supply of vitamins is absolutely necessary for health and growth and absence of which results in a deficiency disorder. b. Name of the vitamin or element Origin (important source) One major biochemical reason for importance to organism Calcium Milk, egg-yolk, cheese, beans Calcification of bone and teeth Iodine Sea-foods Needed to form part of molecule of hormone tyroxine Iron Meat, egg-yolk, fish, green leafy vegetables Transport of gases. And participation in cellular oxidation mechanism Vitamin A Fish liver oil, egg-yolk, butter and milk Precursor of rhodopsin molecule in retina cells D Egg-yolk and fish liver oils, cod liver oil. Absorption, retentiona dn utilization of calcium and phosphorous for mineralization of bones Riboflavin Leafy vegetables and eggs Needed to form coenzyme FAD in respiration. K Green leafy vegetables Synthesis of prothrombin 4. The ileum has a number of structural features that significantly increase the surface area which makes it well adapted for absorption. a. The length of the ileum is very long – about 6 meters in adult humans. The mucous internal lining of the ileum is thrown into folds that increase the surface area and on the folds are numerous finger like projections called villi. These have the form of a finger of a glove. These are most numerous in the upper part of the small intestine. Each villus contains a single lacteal tube, which may be two in case of the larger villi. They also contain capillary vessels near its surface. In addition the villi also contain several muscular fiber cells capable of contraction and extension. This aids in the absorption process. The epithelial cells that cover the extremities of the villi play a major role in the selection and absorption process and then delivering them to the lacteals of the villi, from where they are delivered to the circulation. b. the stomach has a muscular wall that helps it to churn and mix the food with the gastric juice. c. there are glands in the stomach wall that secrete a healthy mucous that acts as a barrier to prevent harmful bacteria from attaching the intestinal wall. d. the same mucous that lines the stomach wall protects it from the harsh chemicals and digestive enzymes. 5. a. Mastication, otherwise called chewing is the first step in the breakdown of complex food stuffs. It breaks the larger food pieces into smaller pieces, thereby increasing the surface area giving way for the digestive enzymes to work. It also helps in softening the food and softening it into a size conducive for swallowing. It also helps to lubricate the food by impregnation with saliva. Digestion: the process of digestion prepares the food for its entrance into the blood stream. The process of chewing and absorption, though closely connected with digestion, are not really implied as many animals that do not chew or have absorbent vessels, digest food. Digestion simple involves two processes, the mechanical process such as maceration which involves reducing the food to a pulp; and the chemical process of decomposition and transformation. b. i) Absorption of sugars: the absorption of the principle sugar glucose and galactose takes place through active transport. A carrier macromolecule is present at the outer surface of the brush border of the intestine which has specific binding sites for the sugars and also Na+ , which increases the affinity of the carrier molecule to the sugar. The carrier molecule after binding moves across the brush border cell membrane and liberates glucose. The energy for this process is supplied by ATP. Absorption of amino acids: this also occurs by a Na+ dependent active transport process mediated by a carrier molecule, similar to glucose absorption. Absorption of lipids: Most of the lipids are absorbed in the small intestine, wgere the lipid emulsion is stabilized by bile salts that coat the emulsion to prevent it from coalescing. This is followed by binding of pancreatic enzymes to the emulsions which digest the lipids. The products of digestion are then incorporated into micelles which are absorbed at the luminal surface of the brush border membrane by simple diffusion ii) the absorbed sugars enters into the capillaries from the intestinal cell lumen through the process of passive diffusion. Once the amino acids are inside the enterocytes they are hydrolyzed and pass into the portal circulation as free amino acids. The digested lipids once inside the enterocytes, are resynthesized into triglycerides and the cholesterol is estrerified. These aggregate to form lipid droplets in the enterocyte cytoplasm. A layer of phopholipid and protein is added to form chylomicrons which enter into the lymphatics. 6. a. the liver is supplied by two large blood vessels : i) the portal vein, which supplies about two thirds of the blood. It brigs with it oxygen and nutrients from intestine. ii) the hepatic artery, providing the rest. It provides oxygen rich blood from the heart. b. i) Liver plays a major role in lipid metabolism. Some fatty acids are synthesized in the liver itself. Those fatty acids derived from the diet or adipose tissue are esterified in the liver, converted to triglycerol, incorporated into phospholipids, or oxidized to carbon dioxide or ketone bodies. Apoproteins that are required for the secretion of triglycerides are also synthesized by the liver. Under conditions of starvation, metabolic breakdown of lipids takes place in the liver, with the production of ketone bodies. Liver is also the principle organ for in vivo cholesterol biosynthesis. Liver also contains a part of enzymes that esterify cholesterol. ii) Amino acids got from the degradation of proteins in the gastrointestinal tract; reach the liver through the portal vein. Most of these amino acids are catabolized to urea synthesis of which takes place in the liver. These amino acids are also used for the syntheses of liver intracellular proteins. Transamination which is an important process in the metabolism of amino acids takes place in the liver. Various intracellular proteins and export proteins are synthesized in the liver. One such important protein is albumin involved in the transport of many substances such as fatty acids and hormones. Blood clotting factors such as prothrombin and fibrinogen are also synthesized by the liver. iii) the regulation of blood sugar levels is needed to ensure a constant supply of glucose to organs like the brain and the erythrocytes which utilize it as the prime source of energy. The entry of glucose into liver cells is not insulin dependent. When the blood glucose level increases, liver increases the glucose utilization for glycogen and fat formation. Likewise when the blood glucose level falls from normal, liver raises the blood sugar level by activating glycogenolysis and gluconeogenesis. All these are mediated through hormones. During starvation liver converts alanine derived from the breakdown of muscle protein to glucose. 7. a. When there is a chemical reaction between two compounds, a minimum amount of excess energy is required to convert the molecules to the reactive state thereby leading to product formation. This energy is called as the activation energy. When the reaction is catalyzed by an inorganic catalyst, the activation energy is decreased. Enzymes are organic catalysts and these further decreases the activation energy compared to organic catalysts. For example the decomposition of H2O2 requires activation energy of about 18,000 cal/mol; this is lowered to 11,700 when colloidal platinum acts as a catalyst. When an enzyme, catalase, catalyses this reaction the activation energy is further lowered to 2000. Hence an enzyme functions to hasten the rate of as chemical reaction. b. i) Most of the enzymes are specific in their action. Each enzyme in their structure possesses an active site that determines the substrate binding capacity of the enzyme. The configuration of the active site is the key for enzyme substrate interaction as it is there that the substrate is converted to the product. Depending on the active site the enzyme may either act on: - one specific type of substrate molecule. - a group of structurally related compounds - on only one of the two optical isomers of a compound - on only one of the geometrical isomers. ii) The active site of the enzyme determines its specificity. 7. a. i) Temperature: enzymes being proteinaceous in nature, the rate of an enzyme catalyzed reaction increases with rise in temperature. For a rise in 10oC, the rate can increase 2 to 3 times. Above a temperature of 60o , enzymes undergo an irreversible change in their structure and hence coagulate. Decreasing temperatures also inactivate the enzyme but this is an irreversible type of change and the enzyme will gain its activity once the temperature is increased. ii) pH: pH is the negative log of H+ ion concentration. The state of ionization of the enzyme protein is also a major determinant of its activity. A change in the pH value of the medium is related to the degree of dissociation; to the electric charge of the enzyme and by this the formation of the enzyme-substrate complex. An enzyme is thus best active at a certain pH value. The activity of the enzyme is affected above or below this pH. iii) Enzyme concentration. In the presence of sufficient substrate the available enzymes will form the enzyme-substrate complex. A higher concentration of enzyme will increase the rate of the reaction until the substrate is completely exhausted, beyond which it has no effect on the rate. However if the enzyme concentration is less, the rate decreases irrespective of the concentration of the substrate. iv) Substrate concentration: increasing substrate concentrations increase the rate of a reaction, until the available enzymes have been saturated with the substrate. Further increase of the substrate, will not affect the rate of the reaction. Reaction rate is slow at low substrate concentrations. b. Competitive or substrate analogue inhibition. In this type of inhibition there is a close structural resemblance between the inhibitor and the substrate. The inhibitor may thus compete with the substrate to combine with the enzyme to form an enzyme-inhibitor complex. The degree of inhibition depends on the relative concentration of the enzyme and substrate. Hence the rate of eh reaction is decreased in the presence of a high concentration of the inhibitor. In Noncompetitive inhibition, there is no competition between the substrate and the inhibitor as the inhibitor has no structural resemblance with the substrate. It instead binds to the enzyme at a site different from the substrate binding site. As a result formation of enzyme-substrate and enzyme-inhibitor complexes occur. But the binding of the inhibitor may alter the configuration of the active site of the enzyme that binds the substrate, thereby affecting the affinity of the enzyme to the substrate and vice versa. Hence the overall rate would depend on the concentration of both substrate and inhibitor. 9. a. Aerobic and anaerobic respiration Aerobic respiration is the oxidation of molecules in the presence of oxygen, and if respiration occurs in the absence of oxygen, it is referred to as anaerobic respiration. For example in humans, Glycolysis is the central pathway of glucose catabolism, the end product of which is pyruvate. The pyruvate can in turn be metabolized to harness energy either aerobically or anaerobically. In aerobic organisms, the pyruvate enters the Kreb’s cycle in the mitochondria and gets completely oxidized to carbon-dioxide and water with the intervention of molecular oxygen.Hence the glucose is completely catabolized to give energy. In case of insufficient supply of oxygen, as in case of vigorously contracting muscles, the pyruvate formed cannot be oxidized further due to lack of oxygen. Under such conditions it is reduced to lactate. The amount of energy gained during such a process is less due to incomplete oxidation of the molecule. b. Aerobic respiration: takes place in the mitochondria. Anaerobic respiration: takes place in tissues like the vigorously contracting skeletal muscles. c. ATP yield: taking the example of glucose oxidation, aerobic respiration that involves oxidation of glucose to 2 molecules of pyruvate, a transition reaction where pyruvate is converted to acetyl – CoA, and then the oxidation of acetyl-CoA through the Kreb’s Cycle and the electron transport chain, would give total of 38 ATP’s. While the anaerobic pathway, which stops with the reduction of pyruvate to lactate will yield only 2 ATP’s. 10. a. Glycolysis It is the central pathway of glucose catabolism. It is the starting point of the catabolism. It is a sequence of 10 enzyme-catalyzed reactions that converts a molecule of glucose to 2 molecules of pyruvate, with the simultaneous production of ATP. A total of 8 ATP’s (2 ATP’s got through substrate level phosphorylation, 6 ATP’s from oxidation of 2 NADH molecules through the electron transport chain)are obtained for every molecule of glucose oxidized through the glycolytic pathway. b. Kreb’s cycle The pyruvate formed in the glycolytic pathway has 2 fates in humans, in the presence of oxygen it can undergo further oxidation through the Kreb’s cycle and form carbon-di-oxide and water or in the absence of oxygen it can get reduced to lactate. In case of aerobic conditions, before it enters the Kreb’s cycle, the two pyruvate molecules undergo oxidative decarboxylation to give 2 acetyl CoA, which enters the Kreb’s cycle. This step is also energy yielding as a total of 6 ATP’s is produced through electron transport system. The Kreb’s cycle consists of 8 enzyme catalysed reaction steps leading to the formation of water and carbon- di-oxide. There is an ATP yield via the electron transport chain, of 12 for one molecule of acetyl-CoA, giving a total of 24 ATP’s. Hence this cycle yields a total of 30 ATP’s. c. Electron transport Chain: In both the above processes, the NADH and FADH molecules produced during the course of the pathway get oxidized back to NAD and FAD to re-enter the pathways, via the electron transport chain. This chain consists of a flow of electrons from organic substrates to oxygen with the simultaneous release of energy for generation of ATP molecules. NADH upon oxidation yields 3 ATP molecules and FADH yields 2 ATP molecules. Hence the complete oxidation of one molecule of glucose through all these pathways will yield. A total of 38 ATP’s b. cellular respiration provides energy in the form of high energy molecules like ATP. And ATP is involved in several cellular processes, especially as a coenzyme for several enzymes. These enzymes may also be involved in the production of macromolecules. Therefore cellular respiration is required to facilitate macromolecule production. 11. a. A = Adenine B = Ribose sugar C= Triphosphate b. The three process are active transport of molecules across cells, muscle contraction, chromatin assembly uses ATP. c. i) True ii) False iii) False iv) True v) False d. the transport of electrons in the electron transport chain releases a lot of energy which is harnessed by the oxidative phosphorylation process, where ADP +pi gives rise to ATP. It is used because it is the most widely distributed high energy compound in the human body, due to the presence of high energy phosphate groups. Hence it is used widely by all organisms as the primary energy currency. e. Most of the ATP in animal cells is generated within the mitochondria. 12. a. Pyruvate b. the reduced NADH is oxidized back to NAD through the electron transport chain. Specific dehydrogenases catalyze the oxidation of NADH back to NAD in the electron transport chain. The process also converts the energy associated with reduced electrons, liberated in the conversion of NADH to NAD. c. Ethanol and Carbon di-oxide d. Reduced NAD, NADH enters the electron transport chain, and gets oxidized to NAD with the concomitant formation of ATP by the process of oxidative phosphorylation using the energy liberated during the oxidation process. . a. Oxidative phosphorylation b. Kreb’s cycle does not directly require oxygen, however it depends on the by-products on the electron transport chain such as oxidized NAD and FAD. This process is aerobic, therefore Kreb’s cycle is an aerobic process. 13 a. The egg-white is a rich source of albumin b. To facilitate a better reaction with the solutions c. It is used as a control d. The overall volume in each tube should be 20 e. 1. In the presence of HCl, pepsin changes into its active form pepsinogen, which digests the albumin. 2. The presence of sodium carbonate does not facilitate the digestion of albumin by pepsin. There will be least digestion in this tube. f. It serves as a control for tube B. it is just to see whether the HCl used is working or not. g. It is produced in the stonmach. 14. a. plot a graph b. i) there is a steady increase in the rate of the reaction with every 10 degree rise in temperature. ii) a decline in the rate of the reaction is seen between these temperatures. c. the optimum temperature is at 45oC d. The pH of the reaction should be kept constant. e. In vitro conditions varies from the in vivo conditions. f. a protein analysis could be done. Read More