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BZYCT-135: Physiology and Biochemistry

BZYCT-135: Physiology and Biochemistry

IGNOU Solved Assignment Solution for 2023

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Assignment Code: BZYCT-135/TMA/2023

Course Code: BZYCT-135

Assignment Name: Physiology and Biochemistry

Year: 2023

Verification Status: Verified by Professor


Note: Attempt all questions. The marks for each question are indicated against it.




Q1i) What prevents the epithelial lining of the walls of the stomach of animals from being digested by the HCI secreted by it? (5)

Ans) The stomach is an organ that stores food and breaks it down mechanically and chemically. Hydrochloric acid (HCl), pepsinogen, mucus, and bicarbonate are some of the things the stomach makes to do these things. The parietal cells of the gastric glands make HCl, which has a pH of about 2. This low pH is needed for pepsinogen to turn into the active enzyme pepsin, which is what breaks down proteins into smaller pieces called peptides.


The mucous cells, parietal cells, and chief cells make up the epithelial lining of the stomach. Several things protect the epithelial lining from the acidic environment of the stomach. Among these tools are:

  1. Mucus Secretion: Mucus cells in the stomach make a thick, sticky mucus that coats the epithelial lining and protects it. This layer of mucus helps to balance out the acidic environment and keeps the acid from touching the epithelial cells directly.

  2. Bicarbonate Secretion: Bicarbonate ions are released by the pancreas into the duodenum. These ions help neutralise the acidic chyme as it leaves the stomach. The bicarbonate ions also move back into the stomach and help neutralise the acid near the epithelial lining.

  3. Tight Junctions: The stomach's epithelial cells are close together and make a barrier that keeps the acid from getting to the tissues below.

  4. Rapid Epithelial Cell Turnover: The stomach's epithelial cells are close together and make a barrier that keeps the acid from getting to the tissues below.

  5. Parietal Cell Regulation: Several hormones, such as gastrin, somatostatin, and histamine, control how the parietal cells of the stomach work. These hormones help control how much HCl is made and stop the body from making too much acid.


But sometimes, the stomach's defences can't keep up, and the epithelial lining can get hurt. This can lead to problems like gastritis, peptic ulcers, and even cancer of the stomach. Infections with Helicobacter pylori, taking nonsteroidal anti-inflammatory drugs (NSAIDs), drinking too much alcohol, and smoking all put you at risk for these conditions.

Q1ii) What are the end-products of food that can be absorbed by the body? Explain how absorption of fats differs from absorption of proteins and sugars. (5)

Ans) Simple sugars, amino acids, fatty acids, glycerol, vitamins, minerals, and water are the end products of food that the body can use. These molecules are made when digestive enzymes in the digestive tract break down carbohydrates, proteins, and fats. Getting rid of these waste products is important for keeping the body's metabolism and other systems working well.


Taking in fats is different from taking in proteins and sugars in many ways. Fats are hydrophobic, which means they don't mix well with water. Proteins and sugars, on the other hand, are hydrophilic and can dissolve in the blood. So, fats must go through a process before they can be taken in by the body.


The first step in getting fat into the body is for bile salts, which are made by the liver and stored in the gallbladder, to break up large fat droplets into smaller ones. This makes the surface area of fat droplets bigger, so pancreatic lipases can work on them. These enzymes turn fats into fatty acids and glycerol, which the cells that line the small intestine, called enterocytes, can take in.

After fats are broken down, fatty acids, glycerol, and bile salts are sent to the enterocyte

membrane, where they are turned back into triglycerides. Then, these triglycerides combine with proteins to make chylomicrons, which are carried to the lymphatic system by lacteals, which are small lymphatic vessels in the villi of the small intestine. The chylomicrons are then sent into the bloodstream, where they are used by cells for energy or stored in adipose tissue.


Proteins and sugars, on the other hand, are taken in by simple diffusion or facilitated diffusion. Proteases break down proteins into amino acids, which are then taken in by the enterocytes through active transport. In the same way, carbohydrases break down sugars into monosaccharides, which are then taken in by the enterocytes through facilitated diffusion.

Once absorbed, the hepatic portal vein takes these end-products to the liver, where they are processed and sent to the rest of the body. The liver is important for controlling how these waste products are broken down, keeping glucose levels stable, and making bile to help digest fat.


Q2a) How is carbon dioxide transported when it is released by the tissues into the blood in mammals? What is the role of carbonic anhydrase? (6)

Ans) Carbon dioxide (CO2) is a waste product produced during cellular respiration in tissues. It diffuses out of the cells and enters the bloodstream where it is transported to the lungs for elimination. In mammals, carbon dioxide is transported in three ways: as dissolved CO2, as bicarbonate (HCO3-) ions, and as carbaminohaemoglobin (HbCO2).


The majority of CO2 (about 70%) is transported in the form of bicarbonate ions. In red blood cells, carbonic anhydrase (CA) catalyses the reaction between carbon dioxide and water to form carbonic acid (H2CO3), which then dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+):


CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+


Bicarbonate ions are transported from the red blood cells to the plasma, where they are replaced by chloride ions (Cl-) in a process called the chloride shift. The bicarbonate ions are transported in the plasma to the lungs, where they are converted back into carbon dioxide through the reverse reaction of the above equation.


Another way that carbon dioxide is transported in the blood is as carbaminohaemoglobin. Carbon dioxide binds to haemoglobin (Hb) in red blood cells to form carbaminohaemoglobin (HbCO2). This process occurs primarily in the tissues where there is a high concentration of CO2. At the lungs, CO2 is released from HbCO2 and is exhaled.


Carbonic anhydrase plays a crucial role in the transport of CO2 in the blood. It is an enzyme found in red blood cells that speeds up the reaction between CO2 and water to form H2CO3. Without carbonic anhydrase, the reaction would be too slow to maintain the necessary equilibrium between CO2, H2CO3, HCO3-, and H+ ions. The absence of carbonic anhydrase can lead to a buildup of CO2 in the blood, a condition known as hypercapnia, which can be life-threatening.


Proteins, carbohydrates, and fats are absorbed differently. Hydrophobic fats make blood transfer difficult. The small intestine breaks them into fatty acids and glycerol. Intestinal epithelium cells rearrange these molecules into triglycerides. Triglycerides, proteins, and phospholipids create chylomicrons, blood-transportable lipoprotein particles. Chylomicrons enter the bloodstream surrounding the heart via the lymphatic system because they are too large for capillaries. Lipoprotein lipase in the blood breaks down chylomicron triglycerides into free fatty acids and glycerol for energy and storage.  Hydrophilic proteins and carbohydrates can circulate without lipoprotein particles. Specialized transporters transfer amino acids into intestinal epithelial cells and the blood from the small intestine. Specialized transporters carry monosaccharides from the small intestine to the circulation.


Q2b) Select the four true statements: (4)

i) Arteries generally have a larger diameter than veins.

Ans) False.


ii) Capillaries are made up of a single layer of endothelial cells surrounded by a basal membrane.

Ans) True.


iii) The arteries near the heart are more elastic and dampen the oscillation in blood flow.

Ans) True.


iv) Whole blood is more viscous than plasma because of the presence of blood cells.

Ans) True.


v) The maximum pressure during a heartbeat is systolic pressure.

Ans) True.

vi) The maximum pressure during a heartbeat is known as diastolic pressure.

Ans) False.


Q3i) Write short notes on: (5)

a) green gland of crustaceans

Ans) The green gland is an organ that many crustaceans, like crabs, lobsters, and crayfish, use to get rid of waste. It is on either side of the cephalothorax, which is the part of the animal where the head and torso are joined.


The green gland gets its name from the fact that it is green. This colour comes from a pigment called coelenterazine, which is found in the gland. This colour is made by coelomocytes, which are specialised cells in the gland.


The green gland's main job is to get rid of metabolic waste from the hemolymph, which is the fluid that moves through the body of crustaceans. This is done by a process called ultrafiltration, which is like how blood is filtered by the kidneys of mammals.


The filtered fluid, called primary urine, then goes through a process in the gland called reabsorption and secretion, which makes final urine. The animal then gets rid of the last bit of urine through a hole at the base of its antennae.


In addition to helping the body get rid of waste, the green gland also helps the body keep the right balance of salt and water. This is called osmoregulation. This is especially important for crustaceans that live in places like estuaries or tidal pools where the salt levels change.


b) Molluscan kidney

Ans) Molluscs are a group of animals that do not have backbones. They include snails, clams, squid, and octopuses, among others. The molluscs kidney, also called the nephridium, is the main organ that these animals use to get rid of waste. Its job is to get rid of waste from the blood and to keep the animal's osmotic balance in check.


Molluscs kidneys are made up of two tubes that run along the length of the body. These tubes are called metanephridia. Nephrocytes are specialised cells that line the metanephridia. They filter the blood and get rid of waste. The body then gets rid of the waste products through urine.


Molluscs urine is made up of different things depending on the species and where the animal lives. Some species' urine is mostly made up of ammonia, while other species' urine is mostly made up of urea. The type of waste product made by a mollusc’s kidney depends on where it lives and how much water is available.

Q3ii) Diagrammatically explain the biochemical pathways that produce ATP for vertebrate muscle contraction. (5)

Ans) The process of ATP production for vertebrate muscle contraction involves a complex interplay of biochemical pathways. There are three primary pathways involved in ATP production: creatine phosphate, anaerobic glycolysis, and aerobic respiration. These pathways are shown in the diagram below.


Creatine Phosphate: The creatine phosphate pathway (also known as the phosphagen system) is the fastest and most immediate means of ATP production. This pathway relies on the availability of creatine phosphate (CP) stored in the muscles. When energy demand increases, creatine kinase catalyses the transfer of a phosphate group from CP to ADP, forming ATP. This reaction is reversible and allows for the rapid regeneration of ATP during short, intense bursts of activity.


Anaerobic Glycolysis: The anaerobic glycolysis pathway is another means of ATP production. This pathway involves the breakdown of glucose to produce ATP in the absence of oxygen. During glycolysis, glucose is converted into pyruvate, which is then converted into lactate. This process produces a net of two ATP molecules. Although the energy yield of anaerobic glycolysis is low, it can produce ATP rapidly and is therefore important for short, high-intensity exercise.


Aerobic Respiration: The aerobic respiration pathway is the most efficient means of ATP production. This pathway involves the breakdown of glucose and other fuels in the presence of oxygen. The products of aerobic respiration are carbon dioxide, water, and ATP. This process yields a net of 36-38 ATP molecules per glucose molecule. Although aerobic respiration is slower than anaerobic glycolysis and the creatine phosphate pathway, it can sustain ATP production for prolonged periods and is therefore important for endurance activities.


The diagram shows how these three pathways interconnect to produce ATP for vertebrate muscle contraction. During short, intense bursts of activity, the creatine phosphate and anaerobic glycolysis pathways are primarily responsible for ATP production. As the duration of exercise increases, the contribution of aerobic respiration to ATP production becomes more significant. The diagram also shows the importance of the electron transport chain in ATP production.


The electron transport chain is the final stage of aerobic respiration and involves the transfer of electrons from NADH and FADH2 to oxygen, forming water. This process generates a proton gradient across the mitochondrial membrane, which drives the production of ATP-by-ATP synthase. ATP synthase is an enzyme that catalyses the phosphorylation of ADP to form ATP. This process is known as oxidative phosphorylation and is responsible for the majority of ATP production during aerobic respiration.


Q4a) If a new compound is used that binds to membrane receptors by blocking them which hormone action will be blocked as a result? (2)

Ans) Depending on the type of receptor and the hormone it interacts with, a compound that binds to and blocks membrane receptors will stop a certain hormone action. Hormones attach to certain receptors on the outside of the cell membrane. This sets off a chain reaction inside the cell that leads to the cellular response.


For example, if the compound binds to insulin receptors in cell membranes, it could stop insulin from working in the body. Insulin is a hormone that controls how much sugar is in the blood by making it easier for cells to take in glucose. If the cells' insulin receptors are blocked, they will not respond to insulin and won't be able to take in as much glucose.


In the same way, if the compound binds to adrenaline or epinephrine receptors, it may stop these hormones from working in the body. Adrenaline and epinephrine are hormones that trigger the "fight or flight" response. This response raises the heart rate, blood pressure, and does other things to the body. If these hormones' receptors are blocked, the body will not be able to handle stress as well as it should.


Q4b) If cAMP formation is inhibited in the cell, then what step in the hormone action will be affected? (2)

Ans) Cyclic AMP (cAMP) is a key second messenger that is involved in many ways that hormones send messages. It is made by the enzyme adenylate cyclase when transmembrane receptors for hormones and neurotransmitters called G protein-coupled receptors (GPCRs) are turned on.

When cAMP formation in a cell is stopped or slowed down, this means that cAMP is not being made. This can happen when the enzyme adenylates cyclase, which makes cAMP, is stopped from doing its job. Because of this, the signalling processes that depend on cAMP will be changed.


The adrenaline pathway is an example of a hormone signalling pathway that depends on cAMP (epinephrine). Adrenaline binds to beta-adrenergic receptors on the surface of cells. This turns on G proteins, which in turn stimulate adenylate cyclase to make cAMP. The protein kinase A (PKA) is then turned on by the cAMP. The PKA phosphorylates target proteins to get a response from the cell.  This route stops cAMP synthesis, slowing or stopping PKA activation. Adrenaline will affect cells less. This can affect different tissues and cells in different ways. Less cAMP in the heart can reduce its pace and contractability. It slows liver glucose release.


Q4c) How can hormones mediate changes in the cell’s function? (2)

Ans) Hormones are chemical signals that play a key role in controlling many of the body's functions. Hormones change how a cell works by attaching to certain receptors on the cell's surface or inside the cell. When the hormone binds to its receptor, it sets off a chain of events that eventually change how the cell works.


When a hormone binds to its receptor on the cell surface, it starts a signal transduction pathway. This can involve the activation of different intracellular signalling molecules, such as cyclic AMP (cAMP), calcium ions (Ca2+), protein kinase C (PKC), or mitogen-activated protein kinase (MAPK) (MAPK). Different enzymes, ion channels, or transcription factors can then be turned on or off by these signalling pathways. This changes how the cell works.


Hormones can also bind to intracellular receptors, which are found inside the cell. Most of the time, these receptors are in the cytoplasm or nucleus. When they bind to a hormone, they move to the nucleus and bind to specific DNA sequences. This controls how genes are expressed. This can cause the cell to make new proteins or change proteins it already has, which can change the way the cell works.


Q4d) What is the role of calcium ion as a second messenger? (4)

Ans) Calcium ion is an especially important part of intracellular signalling pathways because it acts as a second messenger. Calcium ions are important second messengers because they can move quickly and easily through a cell's cytoplasm. This lets them control a wide range of cellular processes. Calcium ions are stored in organelles like the endoplasmic reticulum and the mitochondria. When certain signals happen, like when a hormone binds to a receptor on the cell surface or when a G protein-coupled receptor is turned on, calcium ions are released into the cytoplasm Once calcium ions are released into the cytoplasm, they bind to and activate effector molecules like calmodulin and protein kinase C, which control a wide range of cellular processes like muscle contraction, neurotransmitter release, enzyme activity, gene expression, and cell division. Calcium ions are also an important part of how neurons send messages to each other. Calcium ions are needed for neurotransmitters to be released from the presynaptic terminal and for the strength of synaptic connections between neurons to be controlled.


Q5i) Write the term used for the following: (5)


a) Female reproductive stem cell.

Ans) Oogonium.


b) Mature follicle containing fluid filled spaces.

Ans) Graafian follicle.


c) A soluble polypeptide hormone synthesized by ovary during pregnancy.

Ans) Human chorionic Gonadotropin (hCG).


d) C-21 steroid hormones having basic structure of pregnant nucleus.

Ans) Progestogens


e) Luteotropic hormone of pituitary.

Ans) Luteinizing hormone (LH).


Q5ii) Draw a labelled diagram of a cross section through the mammalian seminiferous tubule. (5)



Q6a) Do as directed. (5)

i) D-Mannose is a ketotriose (True/ False).

Ans) False.


ii) Ribulose is ketopentose or aldopentose (Pick one option)

Ans) Ribulose is an aldopentose.


iii) Molecule with ‘n’ chiral centers has how many stereoisomers?

Ans) A molecule with 'n' chiral centers has 2^n stereoisomers.


iv) D form of carbohydrates is more abundant than L form (True/ False).

Ans) False.


v) Enantiomers are pair of chiral molecules with non-superimposable mirror images (True/ False).

Ans) True.


Q6b) Describe the role of enzymes in lowering the activation energy and in coupled reactions. (5)

Ans) Enzymes are biological catalysts that speed up biochemical reactions by lowering the activation energy needed for the reaction to happen. They do this by giving the reaction another way to go that has a lower activation energy than the way it would go without the catalyst. Enzymes are specific and can only speed up one or a small number of related chemical reactions.


One of the most important things enzymes do is lower the amount of energy a reaction needs to start. In a chemical reaction, the activation energy is the amount of energy needed to get to the transition state, where bonds are breaking and making new ones. By making the transition state more stable, enzymes lower the activation energy and make it easier for the reaction to happen. Enzymes do this by making short-term bonds with the reactants. This brings the reactants closer together and makes it easier for them to react.


Coupled reactions, in which the energy released by one reaction is used to drive another reaction, can also be sped up by enzymes. For example, when the enzyme hexokinase is present, the breakdown of glucose is linked to the making of ATP, which is the cell's energy currency. The breakdown of glucose is an exergonic reaction that releases energy. This energy is then used to phosphorylate ADP to make ATP, which is an endergonic reaction that needs energy input.

Enzymes are a key part of metabolic pathways, which are chains of chemical reactions that make up complex biochemical networks. There are many ways to control how metabolic pathways work. One of these is feedback inhibition, which is when the product of a pathway blocks an earlier step in the pathway to keep the product from being made too much.


Enzymes are also important in a lot of industrial and medical processes. Enzymes, for example, are used to make a lot of different things, like food additives, medicines, and biofuels. Enzymes are also used in tests to find diseases and see how well treatment is working.


Q7i) Derive Michaelis-Menten equation. (5)

Ans) The Michaelis-Menten equation is a mathematical model that describes the relationship between the rate of an enzyme-catalysed reaction and the concentration of substrate. The equation is as follows:


V = (Vmax [S]) / (Km + [S])


where V is the initial velocity of the reaction, [S] is the substrate concentration, Vmax is the maximum velocity of the reaction, and Km is the Michaelis constant, which represents the substrate concentration at which the reaction velocity is half of Vmax.


The derivation of the Michaelis-Menten equation starts with the assumption that the enzyme-substrate complex (ES) is formed reversibly from the enzyme (E) and substrate (S), and that the reaction follows first-order kinetics.


The rate equation for the formation of ES is given by:


d[ES]/dt = k1[E][S] - k-1[ES]


where k1 is the rate constant for the forward reaction and k-1 is the rate constant for the reverse reaction.


The rate equation for the breakdown of ES into product (P) and enzyme is given by:


d[P]/dt = k2[ES]


where k2 is the rate constant for the breakdown of ES.


At steady state, the rate of formation of ES is equal to the rate of breakdown of ES:


k1[E][S] - k-1[ES] = k2[ES]


Rearranging this equation gives:


[ES] = ([E][S]) / (Km + [S])


where Km = (k-1 + k2) / k1 is the Michaelis constant.


The rate of formation of product (P) is given by:

d[P]/dt = k2[ES]


Substituting [ES] from the steady state equation into this equation gives:


d[P]/dt = (k2Vmax[S]) / (Km + [S])


where Vmax = k2[E] is the maximum velocity of the reaction.


Finally, the initial velocity of the reaction (V) is defined as the rate of formation of product (P) at the beginning of the reaction when [S] is much smaller than Km:


V = d[P]/dt ≈ (k2Vmax[S]) / Km


This equation can be rearranged to give the Michaelis-Menten equation:


V = (Vmax [S]) / (Km + [S])


Thus, the Michaelis-Menten equation relates the initial velocity of an enzyme-catalysed reaction to the substrate concentration and the kinetic parameters Vmax and Km. The equation is widely used in enzyme kinetics to determine the kinetic properties of enzymes and to analyse the mechanisms of enzyme-catalysed reactions.


Q7ii) Draw Lineweaver-Burk plot. 5)

Ans) This is known as Lineweaver-Burk plot or double reciprocal plot.


Q8i) List the Antioxidant vitamins and their roles. (5)

Ans) Antioxidants are substances that can protect cells from the harmful effects of reactive oxygen species (ROS), which are made by the body's normal metabolic processes. Antioxidants stop ROS from hurting cells, DNA, and other parts of cells by getting rid of them. Vitamins are some of the most well-known antioxidants, and many vitamins help protect cells from oxidative stress in important ways. Here are some of the most important antioxidant vitamins and what they do:


Vitamin C: Vitamin C is a water-soluble vitamin that is also called ascorbic acid. It is found in many fruits and vegetables. Vitamin C is a powerful antioxidant because it gives up electrons to neutralise free radicals and keep cells from getting hurt by oxidation. It also makes other antioxidants, like vitamin E, and helps make collagen, keep the immune system working, and take in iron.


Vitamin E: Vitamin E is found in nuts, seeds, and vegetable oils because it dissolves in fat. It works by getting rid of free radicals and stopping lipid peroxidation, which is when lipids get oxidised and damage cell membranes. Vitamin E also helps the immune system work and keeps blood from clotting.


Beta-carotene: Beta-carotene is a provitamin A carotenoid that is found in many fruits and vegetables, especially those that are orange or red. Beta-carotene works as an antioxidant by getting rid of free radicals and stopping cells from being damaged by oxidation. It also helps keep your skin, eyes, and immune system in good shape.


Vitamin A: Vitamin A is a fat-soluble vitamin that can be found in liver, egg yolks, and some plant foods like sweet potatoes and carrots. As an antioxidant, vitamin A gets rid of free radicals and keeps cells from getting hurt by oxidation. It also helps your eyes see, your immune system work, and your skin and mucous membranes stay healthy.


Vitamin D: Vitamin D is a fat-soluble vitamin that is made when the skin is exposed to sunlight. It can also be found in foods like fatty fish and dairy products that have been fortified. Vitamin D is an antioxidant that protects cells from damage caused by free radicals. It has also been shown to reduce inflammation. It also helps keep bones healthy and keeps the immune system working well.


Q8ii) Discuss the consequences of free radical interaction with macromolecules. (5)

Ans) Free radicals are chemical species that have an outer shell electron that is not paired with another electron. When these radicals interact with macromolecules like proteins, lipids, and DNA, they can damage cells, which can lead to several diseases. In this answer, we'll talk about what happens when free radicals meet macromolecules.


Lipid peroxidation: Lipids become peroxidised when free radicals mix with the unsaturated fatty acids in the cell membrane. This causes lipid peroxides to form, which are highly reactive molecules that can start a chain reaction that damages more cells. Lipid peroxidation can cause membranes to become less stable, and a buildup of damaged lipids can lead to the development of long-term diseases like atherosclerosis.


Protein oxidation: Protein oxidation can also be caused by free radicals reacting with amino acid residues. This can change how the protein is made and how it works, which can lead to cellular dysfunction. Protein oxidation has been linked to the development of several diseases, such as Alzheimer's and Parkinson's.


DNA damage: When they come in contact with DNA, free radicals can cause damage to the molecule. This can lead to cancer and other genetic illnesses by causing mutations, chromosomal alterations, and breaks in DNA strands. All of these things can be caused by this.


Inflammation: Inflammation can also be caused by free radicals because they stimulate the production of cytokines and chemokines, which both serve to exacerbate existing inflammation. This can result in damage to the tissues and can lead to chronic diseases such as arthritis in the long run.


Aging: There is a correlation between damage caused by free radicals and getting older. The accumulation of damage caused by free radicals over time can contribute to cellular senescence. When this happens, cells stop operating as efficiently, and the likelihood of being ill increases dramatically.


Q9a) What is glycogenesis? Explain the steps involved in the process of glycogenesis. (5)

Ans) Glycogenesis is the process by which glucose molecules are changed into glycogen and stored in the liver and muscles. This process happens in the fed state when blood glucose levels are high and extra glucose needs to be taken out of the blood and stored for later use. Here are the steps that make up the process of glycogenesis:

  1. Glucose Uptake: The liver or muscle cells take glucose out of the blood and put it into their cells. This is the first step in glycogenesis. The glucose transporter GLUT4 oversees this process.

  2. Conversion of Glucose to Glucose-6-phosphate: Once glucose is inside a cell, the enzyme hexokinase changes it into glucose-6-phosphate (G6P). This reaction cannot be turned back on itself, and it needs ATP to happen.

  3. Conversion of Glucose-6-phosphate to Glucose-1-phosphate: The enzyme phosphoglucomutase then changes G6P to G1P, which is glucose-1-phosphate.

  4. Formation of UDP-glucose: UDP-glucose pyro phosphorylase is the enzyme that changes G1P into UDP-glucose. UDP-glucose is an intermediate that has a lot of energy and is used to make glycogen.

  5. Glycogen Synthesis: The enzyme glycogen synthase then adds UDP-glucose to a growing chain of glycogen, making -1,4-glycosidic bonds. The glycogen branching enzyme then adds -1,6-glycosidic bonds to the glycogen molecule to make branches.

  6. Glycogen Storage: The new glycogen molecule is then put into granules and stored in the liver or muscle cells.


A number of hormones and enzymes are responsible for regulating the glycogenesis process. Insulin facilitates glycogenesis by increasing the amount of glucose that is taken into the body and the amount of glycogen that is produced. Glucagon, on the other hand, inhibits glycogenesis by promoting the breakdown of glycogen, which in turn results in the release of glucose. The phosphorylation and dephosphorylation of glycogen synthase are under the control of the enzyme’s glycogen synthase kinase and protein phosphatase 1, respectively. Because of this, the function of glycogen synthase is altered

Q9b) Explain how is fatty acid synthesis regulated? (5)

Ans) Fatty acid synthesis is a complicated process that is controlled by hormones, enzymes, and the availability of substrates, among other things. Controlling fatty acid synthesis is important for keeping energy balance and making sure cells have enough fatty acids for making membranes and storing energy. In this answer, we will talk about the main things that control fatty acid synthesis, such as hormones, enzyme activity, and the availability of substrates.


Hormonal regulation: Fatty acid synthesis is controlled in a big way by how hormones work. One of the hormones that controls this process is insulin. When blood glucose levels are high, the pancreas releases insulin, which tells cells, such as those in the liver and fat, to take in glucose. Once glucose gets into the cells, it is broken down into pyruvate, which is then turned into acetyl-CoA through a series of chemical reactions. Acetyl-CoA is the building block for making fatty acids, and insulin makes the enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase work faster (FAS). Insulin also stops hormone-sensitive lipase (HSL) from making free fatty acids by breaking down stored triglycerides.


Enzyme regulation: Another important thing that controls fatty acid synthesis is the activity of enzymes. Acetyl-CoA carboxylase (ACC) and fatty acid synthase are two enzymes that are very important to this process (FAS). ACC helps turn acetyl-CoA into malonyl-CoA, which is a key regulatory step in the process of making fatty acids. Malonyl-CoA stops long-chain fatty acids from getting into mitochondria, which slows down their oxidation and speeds up their addition to triglycerides. FAS is in charge of speeding up the process of adding two-carbon units to acetyl-CoA in order to make palmitic acid, which is the building block for fatty acids with longer chains. FAS is controlled by insulin, malonyl-CoA, and phosphorylation, among other things.


Substrate availability: The availability of substrates, such as acetyl-CoA and NADPH, is also a critical factor in the regulation of fatty acid synthesis. Acetyl-CoA is generated by the breakdown of carbohydrates, fatty acids, and amino acids, and its availability is regulated by a variety of factors, including hormonal control and metabolic pathways. NADPH is generated by the pentose phosphate pathway and other metabolic pathways, and it is a critical cofactor for the reductive reactions involved in fatty acid synthesis.


Q10i) Choose the correct answer from the parentheses. (6)


a) (Creatinine/Urea) …………… is the main nitrogenous compound in urine.

Ans) Urea is the main nitrogenous compound in urine.


b) Transamination reaction in amino acid synthesis is catalysed by enzyme ……………. (Decarboxylase/Transaminase).

Ans) Transamination reaction in amino acid synthesis is catalysed by enzyme transaminase.


c) Urea cycle is also referred to as …………. (Krebs-Henseleit/Krebs) cycle.

Ans) Urea cycle is also referred to as Krebs-Henseleit cycle.

d) In deamination, amino acid is converted into ………….(keto acid/ carboxylic acid).

Ans) In deamination, an amino acid is converted into a keto acid.


e) Process of breakdown of amino acids to α keto acids is called …………. (Cis amination/transamination).

Ans) Process of breakdown of amino acids to α keto acids is called transamination.


f) The alpha amino groups of all the amino acids is finally channelised to …………. (glutamate/alanine).

Ans) The alpha amino groups of all the amino acids is finally channelized to glutamate.


Q10ii) Answer in 1-2 lines: (4)


a) Define deamination.

Ans) Deamination is a biochemical process in which an amino group (-NH2) is removed from an amino acid or other nitrogen-containing compound. This makes a corresponding keto acid and ammonia. This process is important for breaking down amino acids and making amino acids that are not needed.


b) Give glutamate dehydrogenase reaction (GDH Reaction).

Ans) Glutamate dehydrogenase helps the oxidative deamination of glutamate into -ketoglutarate and ammonia, which can happen in both directions. Here is how the response is written:


Glutamate + NAD(P)+ + H2O ↔ α-Ketoglutarate + NH4+ + NAD(P)H


c) Name the major transport form of ammonia.

Ans) glutamine is the main way that the body gets rid of ammonia. When different metabolic processes produce ammonia, it is quickly turned into glutamine in high-energy-metabolizing tissues like the liver, brain, and muscle. It is then moved to other tissues where it can be released and used for different things.


d) Defect/deficiency in which enzyme of the urea cycle causes hyperammonaemia?

Ans) Hyperammonaemia can be caused by a problem with any of the six enzymes or two transporters in the urea cycle. The most common problems are with the ornithine transcarbamylase (OTC) and carbamoyl phosphate synthase 1 (CPS1) enzymes.

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