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MFN-002: Nutritional Biochemistry

MFN-002: Nutritional Biochemistry

IGNOU Solved Assignment Solution for 2022-23

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Assignment Code: MFN-002/AST-1/TMA-1/22-23

Course Code: MFN-002

Assignment Name: Nutritional Biochemistry

Year: 2022-2023

Verification Status: Verified by Professor


Section A –Descriptive Questions (80marks)


There are eight questions in this part. Answer all questions.


1. a) Define isomers. Explain stereo isomerism and optical isomerism of monosaccharides in detail. (2+4)

Ans) Isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties.


Stereo isomerism: When a compound has more than one form due to a varied spatial arrangement of the groups linked to an asymmetric carbon atom, stereo isomerism has taken place.


Asymmetric carbon atoms are those found in compounds where each carbon atom is linked to four distinct groups or atoms. This discovery suggests that monosaccharides can take one of two alternative forms, called "D-sugar" or "L-sugar," depending on how they relate to the orientation of the -OH group on the second carbon atom. The -OH group will be on the right side of the bottom carbon atom in the D form, whereas it will be on the left side in the L form. The simplest three-carbon naturally occurring glyceraldehyde’s are D and L forms, which are mirror reflections of one another and lack a plane of symmetry. Since they include four distinct groups on their carbon atoms, carbohydrates are chiral substances in this respect. Most monosaccharides that are present in mammalian metabolism have a D-configuration.


Optical isomerism: When a compound spins the plane of vibration of polarised light rays passing counterclockwise, it is referred to as dextrorotatory or a "d isomer" of the substance, and when it rotates the plane in an anticlockwise direction, it is referred to as laevotatory or a "isomer" of the material. It is possible for two substances with the same chemical formula to have differing optical properties. When a material with optical activity

b)List any two chemical properties of the following: (2+2)


i) Fatty acids


Esterification: Fatty acids and other alcohols can combine to generate esters, just like any other organic acid. Esters like mono- and di-acylglycerols are created when a fat or oil reacts with an alcohol like glycerol. Food components including mono- and diglycerides, lecithin, and other emulsifiers can be produced by reacting edible acids, fats, and oils with edible alcohols through the esterification process.


Soap formation: Metallic salts of fatty acids, also known as "soaps," are created when fatty acids and alkalies combine. Compared to sodium soap, potassium soap of fatty acids is more water soluble.


ii) Proteins


Isoelectric pH: The molecule of a protein contains several ionizable groups. Some of these groups function as proton donors, while others function as proton acceptors, depending on the pH of the medium. Proteins are therefore amphoteric substances. The protein exists as a dipolar ion (one positive and one negative ion) or zwitterion at a particular pH. Therefore, at this pH, the protein's net charge is zero. This pH is sometimes referred to as the protein's isoelectric pH or pI. Protein does not travel to either electrode in an electric field because it has no net charge.


Solubility: In solutions, proteins behave differently. Compared to elongated fibrous proteins like keratins, globular proteins are often more soluble in water. However, the composition of the solvent, pH, temperature, and other factors can affect how proteins behave when they are dissolved.


2. a)Define protein and its monomeric unit. Give classification of amino acid with the structural formula. (2+4)

Ans) Proteins are compounds of carbon, hydrogen, oxygen and nitrogen. On an average, proteins contain 16% nitrogen. Most proteins also contain sulphur and some proteins contain iron, copper, phosphorus and zinc. Proteins are, in fact, polymers consisting of chains of monomeric units. The chains are essentially linear and contain no branches. The monomeric units of proteins are amino acids.


Amino acids are classified into four broad groups according to themature of the side chain (R group). These are:


Amino acids with nonpolar or hydrophobic side chain


b) Briefly describe physio chemical properties of fat-soluble vitamin. (4)

Ans) Vitamins A, D, E, and K are called the fat-soluble vitamins, because they are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats.


Because they lack ionizable groups and are hydrophobic, or water-repelling, substances, fat-soluble vitamins can only be effectively absorbed when there is normal fat absorption. In other words, bile, which aids in the digestion and absorption of different dietary lipids, is also required for the absorption of certain lipid soluble vitamins. Therefore, in addition to inadequate dietary intake, illnesses like steatorrhea (fatty diarrhoea) and biliary system problems that interfere with fat-soluble vitamin digestion and absorption can all result in deficient syndromes linked to that specific vitamin. They are either coupled to particular binding proteins or carried in the blood as components of lipoprotein molecules.

3. a) Define enzyme and coenzyme. Explain models for mechanism of enzyme action in detail with diagram. (2+4)

Ans) Enzyme: Enzymes are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products.


Coenzyme: A coenzyme is an organic non-protein compound that binds with an enzyme to catalyze a reaction. Coenzymes are often broadly called cofactors, but they are chemically different. A coenzyme cannot function alone, but can be reused several times when paired with an enzyme.


Models for mechanism of enzyme action


According to this model, an active site is a region of the enzyme, which bears a specific shape or conformation.  Lock and key hypothesis have a simple approach, which says that the particular substrate perfectly fits into the enzyme’s cleft (active site) for the reaction to occur. Similarly, the way one specific key fits into the notch of a lock and unlocks it.

The Induced Fit Model: According to the induced fit model, the enzyme’s active site is not a completely rigid fit for the substrate Instead, the active site will undergo a conformational change when exposed to a substrate to improve binding This theory of enzyme-substrate interactions has two advantages compared to the lock and key model:


5)     It explains how enzymes may exhibit broad specificity (e.g. lipase can bind to a variety of lipids)

6)     It explains how catalysis may occur (the conformational change stresses bonds in the substrate, increasing reactivity.

b) What are essential fatty acids? Name any two essential fatty acids and their food sources. (4)

Ans) EFAs must be included in the diet on a regular basis. To survive and maintain our health, we must have them. They cannot be produced by our bodies from other materials. We must receive a sufficient amount from outside sources, such as food or supplements. The health of humans depends on two fatty acids. The first is the linoleic acid-containing omega-6 EFA (LA). Safflower, sunflower, and corn polyunsaturated oils are widely available in LA. Alpha-linolenic acid (LNA), also known as ALNA, is the second EFA and is referred to as an omega 3 EFA. LNA, which is often referred to as super-unsaturated, is widely present in hemp and flex seeds.


The polyunsaturate omega 6 family includes LA and its derivatives. This family also comprises gamma-linoleic acid (GLA), dihomogammalinolenic acid (DGLA), and arachidonic acid in addition to linoleic acid (LA) (AA).


LNA and its derivatives are superstaurates in the omega 3 family. This family also comprises stearidonic acid (SDA), eicosapentaenoic acid (EPA), and docosahexaenoic acid in addition to alpha-linolenic acid (LNA) (DHA). Our cells produce SDA, EPA, and DHA if diets contain LNA.

4. a) Explain urea cycle. (5)

Ans) The conversion of ammonia into urea through a series of biochemical reactions is known as the urea cycle or ornithine cycle. It takes place in the liver with the help of mitochondrial and cytosolic enzymes. It is an important pathway in amphibians and mammals as they help in disposing highly toxic ammonia by converting it into urea. The animals that excrete in the form of urea are called ureotelic.


The urea cycle was discovered by Hans Krebs and Kurt Henseleit in 1932. Ammonia is produced in our bodies by amino acid catabolism, deaminations and prolonged starvations. All animals need to excrete ammonia in one way or another. Animals that directly excrete ammonia, such as aquatic organisms are called ammonotelic.


Mammals and amphibians cannot excrete ammonia directly, so they convert it into a simpler form of urea. The urea converted in the liver is transported to the kidney via the bloodstream and then finally excreted in the form of urine. This process is important because, if the nitrogenous waste is not excreted, it starts building up in the body and can be detrimental. Urea is inert in nature, soluble in water and can be easily excreted in urine, whereas ammonia is highly toxic.


The overall reaction equation of the urea cycle is:


NH3 + CO2 + aspartate + 3 ATP + 3 H2O → urea + fumarate + 2 ADP + 2 Pi + AMP + PPi + H2O


b) Explain ß-oxidation of fatty acid. (5)

Ans) fatty acids provide highly efficient energy storage, delivering more energy per gram than carbohydrates like glucose. In tissues with high energy requirement, such as heart, up to 50–70% of energy, in the form of ATP production, comes from fatty acid (FA) beta-oxidation.


During fatty acid β-oxidation long chain acyl-CoA molecules – the main components of FAs – are broken to acetyl-CoA molecules.


Beta-oxidation consists of four steps:

  1. Dehydrogenation catalyzed by acyl-CoA dehydrogenase, which removes two hydrogens between carbons 2 and 3.

  2. Hydration catalyzed by enoyl-CoA hydratase, which adds water across the double bond.

  3. Dehydrogenation catalyzed by 3-hydroxyacyl-CoA dehydrogenase, which generates NADH.

  4.  Thiolytic cleavage catalyzed beta-ketothiolase, which cleaves the terminal acetyl-CoA group and forms a new acyl-CoA which is two carbons shorter than the previous one.


The shortened acyl-CoA then reenters the beta-oxidation pathway.


5. a) What is the role of pancreas in digestion of food? Explain. (5)

Ans) pancreas plays a big role in digestion. It is located inside our belly (abdomen), just behind our stomach. It's about the size of our hand. During digestion, our pancreas makes pancreatic juices called enzymes. These enzymes break down sugars, fats, proteins, and starches. Our pancreas also helps our digestive system by making hormones. These are chemical messengers that travel through our blood. Pancreatic hormones help regulate our blood sugar levels and appetite, stimulate stomach acids, and tell our stomach when to empty.


Pancreas creates natural juices called pancreatic enzymes to break down foods. These juices travel through our pancreas by tubes called ducts. They empty into the upper part of our small intestine called the duodenum. Each day, our pancreas makes about 8 ounces of digestive juice filled with enzymes. These are the different enzymes:


Lipase. This enzyme works together with bile, which our liver produces, to break down fat in our diet. If we don't have enough lipase, our body will have trouble absorbing fat and the important fat-soluble vitamins (A, D, E, and K). Symptoms of poor fat absorption include diarrhea and fatty bowel movements.


Protease. This enzyme breaks down proteins in our diet. It also helps protect us from germs that may live in our intestines, such as certain bacteria and yeast. Undigested proteins can cause allergic reactions in some people.


Amylase. This enzyme helps break down starches into sugar, which our body can use for energy. If we don’t have enough amylase, we may get diarrhea from undigested carbohydrates.

b) How does the HMP pathway differ from glycolysis? Discuss the metabolic significance of HMP pathway in detail.(5)

Ans) The interconversion processes of the HMP pathway can operate in a variety of orientations, unlike glycolysis or the citric acid cycle, where the direction of the reactions is clearly specified. The supply and demand for cycle intermediates at any one time affect the reaction's rate and direction. Glycolysis and the HMP pathway both take place in the cell's cytoplasm. C02, which is not formed during glycolysis, is a distinctive byproduct of the HMP route. Additionally, this pathway does not produce any ATP, which as we are aware is the main byproduct of glycolysis. In contrast to glycolysis, which employs NAD', oxidation requires NADP+.


Metabolic Significance of HMP Pathway


The HMP route's distinctive product, CO, is not produced via the Embden-Meyerhof pathway. Fatty acids and purine bases are both synthesised using the CO that is produced in this process.


For the synthesis of fatty acids, cholesterol, steroids, and amino acids via glutamate dehydrogenase outside the mitochondria, the reduced form of NADP (NADPH) is used. In fact, the liver, adipose tissue, and lactating mammary glands—tissues that specialise in active lipogenesis—all have active HMP pathways.


The synthesis of nucleic acids and nucleotides uses the pentose sugars generated by the HMP shunt.


The activity of glucose-6-phosphate dehydrogenase is low in skeletal muscle. However, it can produce ribose-5-phosphate just like the majority of other tissues. The transketolase and transaldolase enzymes, along with fructose-6-phosphate and glyceraldehyde-3-phosphate, are likely used to reverse the shunt process in order to do this. In the Embden-Meyerhof pathway for glycolysis, fructose-6-phosphate and glyceraldehyde-3-phosphate are both used. Therefore, a tissue can produce ribose-5-phosphate even if its HMP pathway is not fully functional.


6. a) Work out the energy (ATP) production when glucose is oxidized in the Glycolysis and citric acid cycle pathways. (Illustrate the cycle and work out the ATP production) (4+4)

Glycolysis ultimately splits glucose into two pyruvate molecules. One can think of glycolysis as having two phases that occur in the cytosol of cells. The first phase is the "investment" phase due to its usage of two ATP molecules, and the second is the "payoff" phase. These reactions are all catalyzed by their own enzyme, with phosphofructokinase being the most essential for regulation as it controls the speed of glycolysis.


Glycolysis occurs in both aerobic and anaerobic states. In aerobic conditions, pyruvate enters the citric acid cycle and undergoes oxidative phosphorylation leading to the net production of 32 ATP molecules. In anaerobic conditions, pyruvate converts to lactate through anaerobic glycolysis. Anaerobic respiration results in the production of 2 ATP molecules. Glucose is a hexose sugar, meaning it is a monosaccharide with six carbon atoms and six oxygen atoms. The first carbon has an attached aldehyde group, and the other five carbons have one hydroxyl group each. During glycolysis, glucose ultimately breaks down into pyruvate and energy; a total of 2 ATP is derived in the process


(Glucose + 2 NAD+ + 2 ADP + 2 Pi --> 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O).


The hydroxyl groups allow for phosphorylation. The specific form of glucose used in glycolysis is glucose 6-phosphate.


b) What are free radicals and antioxidants? Give examples of each.(2)

Ans) Antioxidants: An antioxidant is any substance that inhibits or prevents cell antioxidants, free radicals, etc. The compounds known as antioxidants act to lessen the harm that free radicals, or charged particles found in the environment and produced by bodily processes, cause to cells and DNA. Antioxidants are substances that work with free radicals in the body to keep us healthy and active for the duration of our lives.


Example: The most frequent type of biological oxidation is dehydrogenation.


Free radical: Atoms or molecules having an unpaired electron are known as free radicals. The production of biological energy relies heavily on oxidation-reduction reactions. An oxidation-reduction reaction involves the transfer of electrons from one substance to another. An oxidising agent is a chemical that reduces itself while gaining electrons in an oxidation-reduction reaction. A material that provides electrons and undergoes oxidation called a reducing agent. Because reduction always follows oxidation, there must be both an oxidising and a reducing agent.


Example: Hydrogen peroxide.


7. a) Explain the following: (5)


(i) Role of Vitamin A in the visual cycle.

Ans) The role of vitamin A in the visual cycle is specifically related to the retinal compound. Retinol is converted by the enzyme RPE65 within the retinal pigment epithelium into 11-cis-retinal. Within the eye, 11-cis-retinal is bound to the protein opsin to form rhodopsin in rod cells and iodopsin in cone cells. As light enters the eye, the 11-cis-retinal is isomerized to the all-trans form. The all-trans-retinal dissociates from the opsin in a series of steps called photo-bleaching. This isomerization induces a nervous signal along the optic nerve to the visual center of the brain.


After separating from opsin, the all-trans-retinal is recycled and converted back to the 11-cis-retinal form by a series of enzymatic reactions, which then completes the cycle by binding to opsin to reform rhodopsin in the retina.[5] In addition, some of the all-trans-retinal may be converted to all-trans-retinol form and then transported with an interphotoreceptor retinol-binding protein to the retinal pigmented epithelial cells. Further esterification into all-trans-retinyl esters allow for storage of all-trans-retinol within the pigment epithelial cells to be reused when needed. It is for this reason that a deficiency in vitamin A will inhibit the reformation of rhodopsin, and will lead to one of the first symptoms, night blindness.


(ii) Role of Vitamin D in the intestinal absorption of calcium in our body.

Ans) When calcitriol from the blood enters the cytoplasm of the intestinal mucosal cell, it interacts to a particular protein (receptor). This complex travels to the nucleus where it binds to a particular DNA sequence. This activates the RNA polymerase 11 enzyme. This enzyme, as its name implies, aids in the creation of a particular mRNA. Transport of the mRNA to the cytoplasm. Here, it binds to a ribosome and causes the translation of a particular calcium-binding protein known as calbindin. Per protein molecule, one calcium atom is attached. This protein enters the intestinal lumen after digestion, binds to calcium ions, and then transfers the bound calcium. This subsequently enters the bloodstream and increases the blood calcium level, which has fallen. Vitamin's function in maintaining calcium homeostasis We would understand that parathyroid hormone and calcitriol act together. When the amount of serum calcium is low, the parathyroid gland releases this hormone. High PTH levels encourage the production of calcitriol, increases the absorption of calcium in the intestine. PTH and calcitriol work together in the bone to promote bone resorption (demineralization). Finally, calcium excretion in the kidney is inhibited by PTH and calcitriol, which promote calcium resorption in the distal renal tubules. when there is a high serum calcium level. PTH production is stopped. The production of the inactive 24,25 dihydroxycholecalciferol is increased by low PTH levels. As a result, calcium excretion is increased and bone resorption is inhibited. Thus, it is clear that the activity of PTH and vitamin D are strongly related. Additionally, the thyroid gland releases the hormone calcitonin (CT) when the serum calcium level is high. The kidney is where CT works to enhance calcium excretion, which lowers serum calcium levels. CT prevents the resorption of bone.


b) What is inborn error of metabolism? Enlist the disease related to carbohydrate metabolism and explain anyone.(5)

Ans) Rare genetic (inherited) abnormalities known as inborn errors of metabolism prevent the body from correctly converting food into energy. The illnesses are typically brought on by flaws in particular proteins (enzymes) that aid in the breakdown (metabolization) of various food components.


Disease related to carbohydrate metabolism

  1. Pentosuria

  2. Fructosuria

  3. Hereditary fructose intolerance

  4. Galactosemia

  5. Hereditary lactose intolerance

Fructosuria: Fructosuria, disturbance of fructose metabolism resulting from a hereditary disorder or intolerance. Normally, fructose is first metabolized in the body to fructose-1-phosphate by a specific organic catalyst or enzyme called fructokinase. In fructosuria this particular enzyme is defective, and the concentration of fructose increases in the blood and urine. There are no other clinical manifestations or disabilities, and the condition is compatible with normal life expectancy.


8. a) Describe the biochemical role of the hormones produced by the following glands in our body: (5)


(i) Adrenal Medulla

Ans) Dopamine, norepinephrine (noradrenaline), and epinephrine are catecholamine chemicals that are produced by the adrenal medulla (adrenaline). The major product of the α-adrenergic medulla is epinephrine which constitutes 80% of the catecholamines in the adrenal medulla. Catecholamines' direct precursor is tyrosine.


The type of adrenergic receptors that catecholamine hormones bind determines their action. Each one has two subclasses.- α1 and α2 and β1 and β2. The categorization is based on the relative order of binding of different agonists and antagonists (molecules that imitate the action of hormones) (molecules that oppose the action of the hormones). The four basic types of adrenergic receptors respond differently to different catecholamine hormones in terms of binding affinities. Actually, no hormone has a specific affinity for a particular receptor. A hormone may bind to various receptor types. Additionally, the level of affinities for each receptor would differ. Therefore, the impact that a certain hormone can have will rely on the combined impact of each receptor's functions as well as the hormone's affinity for each receptor.


The receptors have a variety of activities, some of which are excitatory and others inhibitory.. P-receptors operate in a similar manner, having both excitatory and inhibitory actions. As a result, a and P receptors are solely identified by the hormone's affinity for the receptors in a particular target organ, not by excitement or inhibition. It is also generally believed that there is a less distinct division of a receptors into α1 and α2 


(ii) Anterior Pituitary

Ans) Corticosteroids are the name for the hormones that the adrenal cortex secretes. All of them are made from cholesterol and have steroid structures. Adrenocortical hormones come in three different varieties: androgens, glucocorticoids, and mineralocorticoids. In terms of importance, the first two hormones are more significant. The secretion of androgens is minimal. The two main types of hormones will be covered next.




The 21-carbon steroids known as glucocorticoids have numerous functions. Their name comes from the fact that one of their most crucial roles is to raise blood glucose levels. The most common glucocorticoid in humans is cortisol, sometimes referred to as hydrocortisone. Although it is less common in humans than in rats, corticosterone is a major glucocorticosteroid. Blood pressure, host defence mechanisms, baseline metabolism, and responses to stress are all impacted by glucocorticoid hormones.




Like glucocorticoids, mineralocorticoids are steroids with 21 carbons. The most active hormone, aldosterone, is responsible for 90% of all mineralocorticoid activity. Aldosterone and deoxycorticosterone both secrete roughly the same amounts, however deoxycorticosterone has just 3% of the mineralocorticoid action of aldosterone. Mineralocorticoid activity is present in even cortisol, the primary glucocorticoid released by the adrenal cortex.


b)Differentiate between the following disease conditions: (5)


i)Maple Syrup Urine Disease and Alcaptonuria

Ans) Difference between Maple Syrup Urine Disease and Alcaptonuria as follows:



ii) Thalassemia and Sickle cell anaemia

Ans) Difference between Thalassemia and Sickle cell anaemia as follows:

Section B - OTQ (Objective Type Questions) (20 Marks)


1. Explain the following in 2-3 sentences. Also give the structure wherever possible. (10)


a. Amylopectin

Ans) Amylopectin is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose. Plants store starch within specialized organelles called amyloplasts. To generate energy, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, an enzyme that assists in breaking down amylopectin, to initiate the hydrolyzation of starch.


b. Galactosemia

Ans) Galactosemia is a rare, hereditary disorder of carbohydrate metabolism that affects the body's ability to convert galactose to glucose. Galactose is a sugar contained in milk, including human mother's milk as well as other dairy products. It is also produced by the human body, and this is called endogenous galactose.


c. Dehydrogenation

Ans) In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At its simplest, it is useful way of converting alkanes, which are relatively inert and thus low-valued, to olefins, which are reactive and thus more valuable. Alkenes are precursors to aldehydes (R−CH=O), alcohols (R−OH), polymers, and aromatics.[1] As a problematic reaction, the fouling and inactivation of many catalysts arises via coking, which is the dehydrogenative polymerization of organic substrates.


d. Porphyrins

Ans) Porphyrins are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins.[1] With a total of 26 π-electrons, of which 18 π-electrons form a planar, continuous cycle, the porphyrin ring structure is often described as aromatic.One result of the large conjugated system is that porphyrins typically absorb strongly in the visible region of the electromagnetic spectrum, i.e. they are deeply colored.


e. Apolipoproteins

Ans) Apolipoproteins are proteins that bind lipids (oil-soluble substances such as fats, cholesterol and fat soluble vitamins) to form lipoproteins. They transport lipids in blood, cerebrospinal fluid and lymph.  The lipid components of lipoproteins are insoluble in water. However, because of their detergent-like (amphipathic) properties, apolipoproteins and other amphipathic molecules (such as phospholipids) can surround the lipids, creating a lipoprotein particle that is itself water-soluble, and can thus be carried through body fluids.


f. Thromboxanes

Ans) Thromboxane is a member of the family of lipids known as eicosanoids. The two major thromboxanes are thromboxane A2 and thromboxane B2. The distinguishing feature of thromboxanes is a 6-membered ether-containing ring.


g. Anaplerotic reaction

Ans) Anaplerotic reactions are chemical reactions that form intermediates of a metabolic pathway. Examples of such are found in the citric acid cycle (TCA cycle). In normal function of this cycle for respiration, concentrations of TCA intermediates remain constant; however, many biosynthetic reactions also use these molecules as a substrate. Anaplerosis is the act of replenishing TCA cycle intermediates that have been extracted for biosynthesis (in what are called anaplerotic reactions).


h. Isozymes

Ans) In biochemistry, isozymes are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. Isozymes usually have different kinetic parameters, or are regulated differently. They permit the fine-tuning of metabolism to meet the particular needs of a given tissue or developmental stage.

i. Mutarotation

Ans) Mutarotation is a difference in the specific rotation of plane-polarized light, due to the change in the equilibrium between two anomers in the solution. Any molecule to show mutarotation must have hemiketal or hemiacetal group. Mutarotation property was first observed in sugar.


j. Zwitterion

Ans) In chemistry, a zwitterion, also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively charged functional groups. With amino acids, for example, in solution a chemical equilibrium will be established between the "parent" molecule and the zwitterion.


2. Name the defective enzyme in the following diseases: (5)


a) Phenylketonuria

Ans) Phenylketonuria, also known as PKU, was first identified in 1933. The disease is brought on by a lack of the phenylalanine hydroxylase enzyme, which breaks down the vital amino acid "phenylalanine" in the body. PKU typically exhibits less than 2% of the normal phenylalanine hydroxylase activity.


b) Tyrosinemia Type I

Ans) Tyrosinosis was the previous name for type I tyrosinemia. Tyrosine and its metabolites abnormally accumulate in the liver as a result of improper tyrosine breakdown, which causes severe liver damage. Hepatorenal tyrosinemia, another name for this condition, is so named because it causes gradual liver and kidney failure. This happens as a result of a fimaryl acetoacetate hydrolase deficit (the terminal enzyme in the tyrosine pathway).

c) Niemann-Pick disease

Ans) The hereditary metabolic disorder known as Niemann-Pick Disease was first identified by Niemann in 1914 and later validated by Pick in 1927. The phospholipid sphingomyelin, which is overly stored in this condition, is a lipid. It is comprised of fatty acids, phosphoric acid, choline, and the amino alcohol sphingosine. Sphingomyelinase, an enzyme that typically breaks down sphingomyelin into phosphorylcholine and ceramide (sphingosine plus a long-chain fatty acid), has a malfunction.


d) Hereditary Lactose intolerance

Ans) Not, as is frequently assumed, a "milk allergy," lactose intolerance is an inability to digest milk sugar caused by a specific lack of the enzyme lactase.



e) Pentosuria

Ans) Pentosuria, inborn error of carbohydrate metabolism, characterized by the excessive urinary excretion of the sugar xylitol. It is caused by a defect in the enzyme xylitol dehydrogenase, by which xylitol is normally metabolized.


3. Match the following: (5)


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