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BZYCT-135: Physiology and Biochemistry

BZYCT-135: Physiology and Biochemistry

IGNOU Solved Assignment Solution for 2021-22

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Assignment Code: BZYCT-135/TMA/2021-2022

Course Code: BZYCT-135

Assignment Name: Physiology and Biochemistry

Year: 2021-2022 (1st July 2021 to 30th June 2022)

Verification Status: Verified by Professor

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

Part-A Maximum Marks: 50

Q1) a) 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) The small intestine absorbs digestive waste after the duodenum (amino acids, simple sugars, fatty acids, glycerol, and nucleotides). They take in the most water, vitamins, and dissolved mineral ions. The type of nutrient absorption across epithelial cells of the small intestine varies. Active transport and the sodium-dependent ATPase pump

Absorption of Fats

Intestinal cells reassemble fatty acids into small fats and pack them inside carrier proteins. Carriers’ proteins deposit fat into cells for energy or storage. Fat digestion takes longer than carbohydrate digestion.

Absorption of Protein

Dietary proteins are three-dimensional chains of amino acids. It allows proteins to enter the bloodstream and reach the cells. Gastric acid relaxes the protein molecule, and a preliminary digestive enzyme breaks it down. Additional enzymes prep specific amino acids for absorption in the small intestine. Faster than protein or fat, carbohydrates are the body's main energy source. Protein digests faster than fat. Some carbs, like sugars and starches, digest faster than others, while others, like fibre, do not.

Enzymes and hormones work together to break down foods into smaller components. For example, eating causes a hormone to release acid and start protein digestion. When food enters the small intestine, it causes the pancreas to release digestive enzymes and the stomach to stop producing acid. These steps combine to break down food and absorb its nutrients.

Q1) b) How is carbon dioxide transported when it is released by the tissues into the blood in mammals? What is the role of carbonic anhydrase? (5)

Ans) Inhalation (breathing) is used in mammals to supply pulmonary ventilation (infoldings of the throat or body surface that enclose respiratory surfaces). Air enters the body during inhalation through the nasal cavity. The nasal cavity warms and humidifies the air as it passes through. Respiratory tissues are protected from direct air contact by mucus. Mucus is very wet. Aeration picks up water from the mucous membrane surfaces. By adjusting the air to the body's needs, these processes help reduce damage from cold, dry air. Mucus and cilia remove particulate matter from the air in the nose. The trachea and lungs are protected by warming, humidifying, and removing particles. Aside from supplying oxygen to the respiratory system, inhalation serves other functions.

Role of carbonic anhydrase

  1. Carbonic anhydrase is an enzyme found in red blood cells, gastric mucosa, pancreatic cells, and renal tubules (H2CO3). Carbonic anhydrase regulates CO2 transport in the blood and is involved in respiration. The enzyme helps the stomach produce hydrochloric acid.

  2. Carbonic anhydrases (CAs) catalyse the bidirectional conversion of CO2 and H2O into bicarbonate (HCO3-) and protons (H+). These enzymes influence many physiological processes within and across the body's many compartments. CAs promote H+ buffering and thus pH-sensitive process stability within compartments. CAs facilitate the exchange of H+, CO2, HCO3-, and related species. This traffic is important for respiration, digestion, and pH regulation.

  3. They are a family of enzymes that catalyse the conversion of carbon dioxide and water to dissociated carbonic acid ions (i.e., bicarbonate and hydrogen ions). Most carbonic anhydrases have a zinc ion active site. They are metalloenzymes. The enzyme regulates pH and transports CO2.

  4. Carbonic anhydrase regulates pH and fluid balance. The enzyme's role varies depending on its location. Carbonic anhydrase, for example, produces stomach acid. The control of bicarbonate ions in the kidney affects cell water content. Controlling bicarbonate ions also affects eye water content. Carbonic anhydrase inhibitors are used to treat glaucoma, or excessive eye water. By inhibiting this enzyme, the patient's fluid balance shifts, reducing pressure.

Q2. a) Describe in brief the cardiac conduction pathway and cardiac cycle. (5)

Ans) The cardiac conduction system is made up of nodes and specialised conduction cells that control and initiate heart muscle contractions. It consists of the following components:

  1. Sinoatrial node

  2. Atrioventricular node

  3. Atrioventricular bundle (bundle of His)

  4. Purkinje fibres.

The sequence of electrical events during one full contraction of the heart muscle:

  1. An excitation signal (an action potential) is created by the sinoatrial (SA) node.

  2. The wave of excitation spreads across the atria, causing them to contract.

  3. Upon reaching the atrioventricular (AV) node, the signal is delayed.

  4. It is then conducted into the bundle of His, down the interventricular septum.

  5. The bundle of His and the Purkinje fibres spread the wave impulses along the ventricles, causing them to contract.

The Cardiac Cycle

The cardiac cycle describes the human heart's activity from the start of one heartbeat to the start of the next. It is divided into two parts: diastole, when the heart muscle relaxes and fills with blood, and systole, when the heart muscle contracts and pumps blood vigorously. The heart relaxes and expands after emptying to receive another influx of blood returning from the lungs and other body systems, before contracting again to pump blood to the lungs and those systems. Before a heart that is normally functioning can pump efficiently again, it must be fully expanded. Each cardiac cycle, or heartbeat, takes about 0.8 seconds to complete assuming a healthy heart and a typical rate of 70 to 75 beats per minute.

Q2) b) Differentiate between artery and vein. (5)

Ans) Arteries are blood vessels that transport oxygen-rich blood from the heart to the rest of the body. Veins are blood vessels that transport oxygen-depleted blood from the body to the heart for reoxygenation. Your arteries transport oxygen-rich blood from your heart to the rest of your body. They branch out into a slew of smaller arteries throughout your body. The aorta is your largest artery. After receiving new oxygen from your lungs, your blood travels through this artery for the first time. The aorta is a blood vessel that runs from your heart to your neck. The aorta branches into smaller arteries that travel up to your head.

As your blood travels through your arteries, it loses oxygen. The blood is carried back to your heart by veins, which allows it to absorb more oxygen. About 75% of the blood that flows through your body is held in your veins. The superior and inferior vena cava are your largest veins. The superior vena cava is a vein that runs from your upper body to your heart. Your inferior vena cava transports blood from all over your body to your heart. These two veins, like arteries, branch off into numerous other veins throughout your body.

Veins, unlike arteries, must generally work against gravity to return blood to the heart. The valves in veins help with this. Inside a vein, these are one-way pairs of flaps. They open to allow blood to flow upwards toward the heart and close to prevent blood from returning downwards. The majority of your body's veins are surrounded by muscle. When you walk, run, or use your muscles in any other way, they squeeze. The blood is forced upwards toward your heart by these squeezes, which push against the vein.

Q3. a) Draw a diagram showing the urine concentration in the nephron. (5)

Ans) The diagram showing the urine concentration in the nephron is shown below:

Q3) b) Explain briefly the role of myosin in muscle contraction. (5)

Ans) Myosin’s are a group of motor proteins that play a key role in muscle contraction and a variety of other eukaryotic motility processes. They are ATP-dependent and are in charge of motility based on actin. Originally, the term was used to describe a group of ATPases found in the cells of both striated and smooth muscle tissue.

The majority of animals use muscular movement as the primary mechanism for a variety of movements. Muscle contraction refers to the ability of muscle to exert force by shortening. This force is the foundation of all internal and external movements in animals. Individual cells move as well: their internal movement is called cytoplasmic streaming, and their external locomotion is caused by amoeboid movement (which gets its name from Amoeba locomotion), cilia, and flagella. Cilia can be found in all animal phyla and are used for a variety of purposes. Cilia (single: cilium) allow entire cells to move in water, as seen in the movement of a single celled paramecium and create currents that move water through the water vascular systems of various invertebrates, including echinoderms.

Q4) a) Explain why an action potential is all-or-none event. (5)

Ans) Because the neuron always depolarizes completely once the threshold potential is reached, action potentials are referred to as "all-or-nothing" events. After depolarization, the cell must "reset" its membrane voltage to the resting potential. In order to accomplish this, the Na+channels close and cannot be opened. Due to a blockage in the sodium channels, the neuron enters its refractory period, during which it is unable to generate another action potential.

K+ channels that are voltage-gated open at the same time, allowing K+ to leave the cell. As K+ ions leave the cell, the membrane potential returns to a negative state. Hyperpolarization occurs when K+ diffuses out of the cell, causing the membrane potential to become more negative than the cell's normal resting potential. At this point, the sodium channels will return to their resting state, meaning they will be ready to open again if the membrane potential rises above the threshold potential. The extra K+ ions eventually leak out of the cell through potassium leakage channels, restoring the hyperpolarized cell to its resting membrane potential.

Q4) b) i) If a new compound is used that binds to membrane receptors by blocking them which hormones action will be blocked as a result? (1)

Ans) G proteins (an enzyme complex linked to a membrane receptor), and protein kinases are both linked to cell surface receptors. Surface receptors can be either stimulatory or inhibitory, and they can bind to G proteins that are either stimulatory or inhibitory. When activated, G proteins bind to guanosine triphosphate (GTP) and can either activate or inhibit adenylyl cyclase, another membrane-bound enzyme.

Q4) ii) If cAMP formation is inhibited in the cell, then what step in the hormone action will be affected? (1)

Ans) When cAMP production is inhibited in a cell, the hormone's action suppresses innate immune functions such as the production of inflammatory mediators and the phagocytosis and killing of microbes.

Q4) iii) How can hormones mediate changes in the cell’s function? (2)

Ans) Hormones bind to specific hormone receptors and cause changes in target cells. Cellular activity is reduced when the number of receptors decreases in response to rising hormone levels, a process known as down-regulation. When a cell expresses a specific receptor for a hormone, it responds to it.

Q4) iv) What is the role of calcium ion as a second messenger? (1)

Ans)  The role of calcium ion as a second messenger is depicted in this image. Calcium ions (Ca2+) play a role in the physiology and biochemistry of cells in living organisms. They are involved in signal transduction pathways, where they act as a second messenger, neurotransmitter release from neurons, all muscle cell contractions, and fertilisation.

Q5) With the help of a flow diagram, explain the function of female hormones in humans. How is it regulated? (10)

Ans) Females naturally produce and secrete a number of hormones, which are controlled by the endocrine system, which includes progesterone and oestrogen. Female hormones, such as oestrogen and progesterone, are secreted by the body to have an impact on a woman's reproductive health. These hormones are referred to as female hormones. Aside from these, the ovaries (the female reproductive organ) also produce testosterone hormones, which are normally considered to be the male hormone. However, these hormones are produced in very small amounts.

Hormones have a variety of important effects on women's health, including their role in fertility and the fact that female hormones are more dominant in women than in men. Hormones have a variety of important effects on women's health, including their role in fertility.

Part-B Maximum Marks: 50

Q6. a) Describe the proteins in terms of levels of organization in primary, secondary, tertiary and quaternary structures. (5)

Ans) The proteins in terms of levels of organization in primary, secondary, tertiary and quaternary structures are as follows:

Primary Structure

Primary structure, the most basic level of protein structure, is simply the sequence of amino acids in a polypeptide chain. Insulin, for example, is made up of two polypeptide chains, A and B. Each chain has its own set of amino acids, which are put together in a specific order. For example, the A chain's sequence differs from the B chains in that it starts with glycine at the N-terminus and ends with asparagine at the C-terminus.

Secondary Structure

Secondary structure, the next level of protein structure, refers to local folded structures that form within a polypeptide as a result of interactions between backbone atoms. (Secondary structure does not involve R group atoms, and the backbone simply refers to the polypeptide chain apart from the R groups.) The helix and the pleated sheet are the two most common secondary structures. Hydrogen bonds form between the carbonyl O of one amino acid and the amino H of another, holding both structures together.

Tertiary Structure

The tertiary structure of a polypeptide refers to its overall three-dimensional structure. Interactions between the R groups of the amino acids that make up the protein are primarily responsible for the tertiary structure.

Quaternary Structure

Many proteins have only three levels of structure and are made up of a single polypeptide chain. Some proteins, however, are made up of multiple polypeptide chains, which are referred to as subunits. When these subunits come together, they form the quaternary structure of the protein.

Q6. b) How temperature and pH affect the rate of enzyme action? (5)

Ans) Temperature, pH, and concentration are all factors that can influence enzyme activity.

Enzymes work best in specific temperature and pH ranges, and they can lose their ability to bind to a substrate if the conditions aren't right.

  1. Temperature: Increasing the temperature of a reaction speeds it up, while decreasing the temperature slows it down. Extremely high temperatures, on the other hand, can cause an enzyme to lose its shape (denature) and cease to function.

  2. pH: Each enzyme has a specific pH range that it prefers. Enzyme activity will be slowed if the pH is changed outside of this range. Enzymes can denature if the pH is too high.

  3. Increased enzyme concentration speeds up the reaction as long as there is a substrate to bind to. The reaction will no longer speed up once all of the substrate has been bound, as there will be nothing for additional enzymes to bind to.

  4. Substrate Concentration: Increasing the substrate concentration speeds up the reaction to a point. Any increase in substrate will have no effect on the rate of reaction once all of the enzymes have bound, as the available enzymes will be saturated and working at their maximum rate.

Q7) a) How a value for Km can be obtained from the vo vs S graph when vo = 1/2 Vmax? (5)

Ans) The substrate concentration that allows the enzyme to achieve half of Vmax is known as the Km or Michaelis constant (maximal velocity). Furthermore, Km has concentration units, but it is unaffected by the concentration of the enzyme or the concentration of the substrate. The inverse of affinity is measured by Km. The affinity of the enzyme for the substrate is measured by the substrate concentration (Km) required to transfer half of the enzyme molecules into the ES complex. Low Km values indicate that the enzyme has a high affinity for the substrate. High Km values, on the other hand, indicate that the enzyme requires relatively high levels of substrate concentration to reach saturation, implying that the enzyme has a low affinity for the substrate.

Km and Vmax are both kinetic variables. When the enzyme is fully saturated with substrate molecules, the rate of reaction reaches its maximum, which is denoted by Vmax. Find the maximum velocity on the graph and divide it in half, i.e., Vmax 1/ 2. Draw a horizontal line from this point to the corresponding point on the graph and read the substrate concentration at that point. The value of Km will be determined as a result of this.

The rate of enzyme activity is calculated as 1/Vo = Km/Vmax (1/[S]) + 1/Vmax, where Vo is the initial rate, Km is the substrate-enzyme dissociation constant, Vmax is the maximum rate, and S is the substrate concentration.

Q7) b) Explain coenzymes and their roles in metabolism. (5)

Ans) A coenzyme is an organic non-protein molecule that connects enzymes. It is an enzyme cofactor that is not a permanent part of the enzyme structure. Cosubstrates are substrates that are loosely bound to the enzyme. ATP and coenzyme A are used in group transfer reactions, while NAD+ and coenzyme Q10 are used in oxidation-reduction reactions. Consumption and recycling of coenzymes an enzyme continuously adds and removes chemical groups. ATP synthase phosphorylates and converts ADP to ATP, while Kinase dephosphorylates ATP back to ADP. Vitamins provide most coenzyme molecules. Adenosine triphosphate and coenzyme A are common sources.

Coenzyme Role as Metabolism

An organic compound that works as a cofactor with enzymes to promote a variety of metabolic reactions. To restore coenzymes to their original state, an enzyme-mediated catalysis reaction is required. NAD accepts hydrogen (and gives it up in another reaction) and ATP gives up phosphate groups while transferring chemical energy (and reacquires phosphate in another reaction). Most B vitamins (see vitamin B complex) are coenzymes, which help move atoms or groups of atoms between molecules to form carbohydrates, fats, and proteins.

Each class of group-transfer reaction is carried out by a specific coenzyme, which is the substrate for a specific set of enzymes. Coenzymes are thus constantly recycled in metabolism. For example, the human body contains about 0.1 mole of ATP. On-going ADP-to-ATP conversion. Thus, the total amount of ATP + ADP is fairly constant. Every day, human cells need to hydrolyze 100-150 moles of ATP, or 50-75 kilogrammes. A human uses up their ATP weight in a day (Di Carlo and Collins 2001). Each ATP molecule is recycled 1000- 1500 times per day.

Q8) a) What is antioxidant? Explain the different types of antioxidants with suitable examples. (5)

Ans) Antioxidants fight free radicals in the body. Free radicals are compounds that can harm your body if they become too abundant. They've been linked to diabetes, heart disease, and cancer. Your body has antioxidant defences to combat free radicals. Antioxidants are found in foods, especially fruits, vegetables, and whole foods. Antioxidants include vitamins E and C. Antioxidant preservatives extend the shelf life of foods.


Types of Antioxidants

Synthetic Antioxidants

synthesis of antioxidants in chemistry, food and medicine Their chemistry is similar to "natural" antioxidants', but they have added new chemical groups that broaden their cellular action or allow them to reach previously inaccessible cell sites. Other antioxidants, however, differ structurally from natural antioxidants, are highly reactive with reactive oxygen species, and provide selective protection in certain tissues. Synthetic antioxidants can stabilise non-food materials like plastics, rubber, and polymers. Synthetic antioxidants in foods, however, require consideration of technological necessity, lipid oxidation product toxicology, and antioxidant toxicology.

Natural Antioxidants

Various plant products are being studied as natural antioxidants to improve the overall quality of meat and meat products. Phosphonic acid from plants has been used extensively in natural antioxidants for meat and meat products preservation. phenolic compounds are found in herbs, fruits, vegetables, grains, cereals, tea, coffee, and red and white wines. These phenols can act as carboxylic acids. There are two types of phenolic compounds. Among plant polyphenols, flavonoids have the most researched antioxidant and biological activities.


Examples of antioxidants include vitamins C and E, selenium, and carotenoids, such as beta-carotene, lycopene, lutein, and zeaxanthin.

Q8) b) Describe the two phases of glycolysis. What is the net outcome of each phase? (10)

Ans) Energy investment and energy generation are the two distinct phases of glycolysis. The glucose molecule is confining in the cell during the first stage of the glycolysis pathway (Energy investment phase). Energy is used to change it so that the 6-carbon sugar molecule divides evenly into two 3-carbon molecules. Energy is extracted from the molecules and stored in the form of NADH and ATP in the second stage of glycolysis (energy generation phase).

Glycolysis is the first of the cellular respiration's main metabolic pathways to produce energy in the form of ATP. Through a series of enzymatic reactions, the six-carbon ring of glucose is cleaved into two three-carbon sugars of pyruvate in two distinct phases. The first phase of glycolysis consumes energy, while the second phase completes the conversion to pyruvate and produces ATP and NADH for use by the cell. Glycolysis results in a net gain of two pyruvate molecules, two ATP molecules, and two NADH molecules for the cell to use as energy. The glycolytic pathway is linked to the Krebs Cycle after the conversion of glucose to pyruvate, where more ATP is produced for the cell's energy needs.

Outcomes of Glycolysis

Glycolysis begins with one molecule of glucose and ends with two molecules of pyruvate (pyruvic acid), four molecules of ATP, and two molecules of NADH. Because two ATP molecules were used to prepare the six-carbon ring for cleavage in the first half of the pathway, the cell now has a net gain of two ATP molecules and two NADH molecules to use. If the cell is unable to further catabolize the pyruvate molecules (via the citric acid cycle or Krebs cycle), it will only be able to extract two ATP molecules from a single molecule of glucose.

Glycolysis can be thought of as a two-step procedure. Energy is consumed in the first phase to generate high-energy intermediates, which then release their energy in the second phase. The energy investment phase necessitates the use of two ATP molecules in order to generate high-energy intermediates. The intermediate is metabolised, yielding four ATP molecules and two NADH molecules in the energy pay out phase.

Q9) a) Discuss the function of Electron Transport Complex-I. (5)

Ans) The electron transport chain (ETC; respiratory chain) is a protein complex that couples electron transfer with proton (H+ ion) transfer across a membrane via redox reactions (both reduction and oxidation occur at the same time). The electron transport chain is made up of peptides, enzymes, and other molecules.


The first complex of the electron transport chain (ETC) catalyses the first step in electron transport by transferring electrons from NADH to coenzyme Q. (CoQ). Complex-I, also known as NADH dehydrogenase, is found in the inner mitochondrial membrane. It contains a flavoprotein (FMN) that oxidises NADH as well as several iron-sulfur clusters, among many other subunits.


The flavoprotein and the iron-sulfur moiety are oxidised and reduced in turn during the electron transport reaction. It all begins with a transfer of electrons from NADH to the flavoprotein. The reduced flavoprotein is then reoxidized, causing the oxidised form of the iron-sulfur protein to be reduced. In the third step, the reduced iron-sulfur protein donates its electrons to coenzyme Q, which is then reduced to CoQH2. Coenzyme Q is also known as ubiquinone. Four protons are transported from the mitochondrial matrix to the intermembrane space when two electrons from NADH are transferred to CoQ.

Q9) b) Describe ketogenesis. Is it a normal physiological process? (5)

Ans) Ketogenesis is a metabolic pathway that results in the production of ketone bodies, which provide the body with an alternative source of energy. In normal circumstances, the body produces small amounts of ketone bodies capable of producing 22 ATP each, which are primarily regulated by insulin. Ketone body production is increased in a state of ketosis when carbohydrates are reduced, and fatty acids are increased. Ketoacidosis, on the other hand, can develop if too many ketone bodies build up, as in the case of uncontrolled diabetes.

Ketogenesis, or the production of ketones for fuel, is a normal, physiologic process that occurs in the mitochondria of liver cells via hepatic beta-oxidation of free fatty acids. Ketones are formed when energy stored as fat in adipose tissue is converted to acetyl-CoA. Extrahepatic tissues can undergo ketolysis and convert ketones back to acetyl-CoA, which then enters the TCA cycle and is used by mitochondria to generate ATP.

Q10) Describe urea cycle. (5)

Ans) The urea cycle (also known as the ornithine cycle) is a series of biochemical reactions that convert ammonia into urea (NH2)2CO (NH3). In ureotelic organisms, this cycle occurs. The urea cycle transforms highly toxic ammonia into urea, which is then excreted.

The urea cycle is a metabolic pathway that converts nitrogen to urea, which is then excreted from the body. Nitrogenous excretory products are primarily excreted in the urine. The highly toxic ammonia is converted to urea, which is nontoxic, highly soluble, and easily excreted by the kidneys. A healthy adult excretes about 30 g of urea per day, which accounts for about 90% of the nitrogenous excretory products. The urea cycle produces urea from NH4+, CO2, and aspartate nitrogen. The cycle takes place primarily in the liver.

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