Assignment Code: MFN-002/AST-2/TMA-2/23-24

Course Code: MFN-002

Assignment Name: Nutritional Biochemistry

Year: 2023

Verification Status: Verified by Professor

Section A –Descriptive Questions

Q1a) What is starch? Give its biochemical structure.

Ans) Definition of starch: Starch is a complex carbohydrate, a polysaccharide, composed of glucose units linked together through glycosidic bonds. It is the most common carbohydrate storage molecule in plants, serving as a long-term energy reserve. Starch is found in various parts of plants, such as roots, tubers, seeds, and grains.

Biochemical Structure:

a) Starch consists of two types of glucose polymers: amylose and amylopectin.

b) Amylose is a linear polymer composed of α-D-glucose units linked by α(1→4) glycosidic bonds. This linear structure results in a helical shape.

c) Amylopectin, on the other hand, is a branched polymer with α-D-glucose units linked by α(1→4) glycosidic bonds, but it also has occasional α(1→6) glycosidic bonds that create branch points. The branched structure allows for multiple ends to be available for enzymatic cleavage.

Q1b) List the important reactions of monosaccharides. Explain any two in detail.

Ans) Reactions of Monosaccharides:

Monosaccharides, the simplest carbohydrates, can undergo various chemical reactions. Two important reactions are oxidation and reduction:

a) Oxidation: Monosaccharides can be oxidized, typically by Benedict's or Fehling's solution, to produce aldehyde or ketone derivatives. For example, glucose can be oxidized to form gluconic acid in the presence of an oxidizing agent, such as Benedict's solution. This reaction involves the reduction of the copper ions in the reagent.

b) Reduction: Monosaccharides can undergo reduction reactions, where aldehyde or ketone groups are converted to alcohol groups. For instance, glucose can be reduced to form sorbitol through the action of a reducing agent like sodium borohydride. This reaction converts the carbonyl group (aldehyde or ketone) to a hydroxyl group.

Q1c) Give an example of a Trisaccharide. What is it made up of?

Ans) An example of a trisaccharide is Raffinose. Raffinose is composed of three monosaccharides: galactose, glucose, and fructose. It is classified as a trisaccharide because it consists of three sugar molecules linked together.

Composition:

a) Raffinose consists of one molecule of galactose, one molecule of glucose, and one molecule of fructose. The glycosidic bonds linking these monosaccharides together are primarily α(1→6) and α(1→2) linkages.

b) Raffinose is commonly found in various plant sources and serves as a source of energy. However, it is also known for its resistance to digestion in the human small intestine, often leading to flatulence when consumed in large quantities.

Q2a)What are Eicosanoids? Briefly describe their role in the body.

Ans) Eicosanoids are a class of signaling molecules derived from arachidonic acid, a 20-carbon polyunsaturated fatty acid. These bioactive lipids play crucial roles in various physiological processes and are involved in both the immune response and inflammation. Eicosanoids include prostaglandins, leukotrienes, and thromboxanes.

Role in the Body:

a) Inflammation: Eicosanoids are involved in the body's response to injury and infection. Prostaglandins, for example, promote vasodilation, increase vascular permeability, and sensitize pain receptors, leading to the characteristic signs of inflammation: redness, heat, swelling, and pain.

b) Immune Response: Leukotrienes are essential in the body's immune response. They mediate the recruitment and activation of immune cells, particularly in allergic reactions and asthma.

c) Blood Clotting: Thromboxanes are eicosanoids that play a role in platelet aggregation and vasoconstriction, contributing to blood clotting and wound healing.

d) Regulation of Blood Pressure: Prostaglandins are involved in the regulation of blood pressure, as they can cause vasodilation (lowering blood pressure) or vasoconstriction (raising blood pressure).

Q2b) Discuss the four basic structural levels of proteins, giving examples.

Ans) Proteins are complex macromolecules with a hierarchical structure consisting of four primary levels:

a) Primary Structure:

The primary structure of a protein is the linear sequence of amino acids linked by peptide bonds. This sequence is unique to each protein. An example is the primary structure of insulin, a hormone with 51 amino acids in a specific sequence.

b) Secondary Structure:

Secondary structure refers to the local folding patterns of the polypeptide chain. The two common secondary structures are α-helices and β-sheets. An example is the α-helical structure found in keratin proteins.

c) Tertiary Structure:

Tertiary structure is the overall three-dimensional conformation of a protein. It is determined by the interactions between amino acid side chains. Haemoglobin, a globular protein, exhibits complex tertiary structure.

d) Quaternary Structure:

Quaternary structure pertains to the arrangement of multiple polypeptide subunits in a multi-subunit protein. Haemoglobin is an example of a protein with quaternary structure, consisting of four subunits.

These structural levels are critical for a protein's function and are intricately linked. The unique sequence (primary structure) dictates how the protein will fold into its secondary, tertiary, and quaternary structures, ultimately determining its specific biological function.

Q3a) List the different classes of enzymes. Explain any two in detail.

Ans) Enzymes can be categorized into several classes based on their functions and the reactions they catalyze.

Two prominent classes are:

a) Oxidoreductases: These enzymes catalyze oxidation-reduction reactions, involving the transfer of electrons between substrates. One well-known oxidoreductase is lactate dehydrogenase (LDH). LDH plays a crucial role in anaerobic respiration and is involved in the conversion of pyruvate to lactate during periods of increased energy demand.

b) Hydrolases: Hydrolases are enzymes that facilitate hydrolysis reactions, where the cleavage of chemical bonds occurs with the addition of water. An essential hydrolase is lipase, which breaks down triglycerides into fatty acids and glycerol. Lipase is critical for the digestion and absorption of dietary fats in the small intestine.

Q3b) Explain briefly the three major classes of enzyme inhibition?

Ans) Enzyme inhibition involves the interference with an enzyme's activity. The three major classes of enzyme inhibition are:

a) Competitive Inhibition: In competitive inhibition, a molecule (the inhibitor) closely resembles the substrate and competes for the enzyme's active site. The inhibitor binds reversibly to the active site, reducing the enzyme's ability to bind the substrate. This can be overcome by increasing the substrate concentration.

b) Non-competitive Inhibition: Non-competitive inhibitors bind to the enzyme at a site other than the active site, causing a conformational change in the enzyme's structure. This change reduces the enzyme's activity and cannot be overcome by increasing substrate concentration.

c) Uncompetitive Inhibition: Uncompetitive inhibitors bind to the enzyme-substrate complex, preventing the release of the product. This type of inhibition only occurs when the substrate is already bound to the enzyme. Like non-competitive inhibition, it cannot be overcome by increasing substrate concentration.

Q3c) Name the enzymes whose blood levels are determined during clinical diagnosis of nephrotic syndrome.

Ans) Enzymes in Clinical Diagnosis of Nephrotic Syndrome:

Nephrotic syndrome is a kidney disorder characterized by the excretion of excess protein in the urine. Several enzymes are not typically measured in diagnosing nephrotic syndrome, as the condition primarily involves proteinuria.

However, specific tests related to kidney function are essential:

a) Serum Creatinine: Creatinine is a waste product of muscle metabolism that is normally filtered by the kidneys and excreted in urine. Elevated serum creatinine levels indicate impaired kidney function, as seen in nephrotic syndrome.

b) Blood Urea Nitrogen (BUN): BUN measures the amount of nitrogen in the blood in the form of urea, another waste product that the kidneys filter. Elevated BUN levels can suggest kidney dysfunction.

These tests help assess kidney function and are often part of the diagnostic workup for nephrotic syndrome. Specific enzymes are not typically the focus of diagnosis in this condition, but rather the evaluation of kidney function and the presence of proteinuria.

Q4a) Describe the role of enzymes in digestion of food in the body.

Ans) Enzymes play a crucial role in the digestion of food within the human body. Digestion is the process by which complex food molecules are broken down into simpler, absorbable substances that can be utilized by the body. Enzymes are biological catalysts that facilitate and accelerate these digestive processes. Here is an overview of the role of enzymes in digestion:

a) Salivary Digestion:

The process begins in the mouth with the secretion of salivary amylase. This enzyme, produced by the salivary glands, initiates the digestion of starches in carbohydrates by breaking them down into maltose, a disaccharide.

b) Stomach Digestion:

In the stomach, gastric lipase is secreted. It plays a role in the digestion of dietary fats, breaking them down into fatty acids and glycerol.

Pepsin is another enzyme produced in the stomach, primarily responsible for digesting proteins. Pepsin cleaves large protein molecules into smaller peptides.

c) Pancreatic Digestion:

The pancreas secretes a variety of digestive enzymes into the small intestine. These include:

i) Pancreatic amylase: Continues the digestion of carbohydrates into simpler sugars.

ii) Trypsin: Digests proteins into peptides.

iii) Pancreatic lipase: Further breaks down fats into fatty acids and glycerol.

iv) Pancreatic nucleases: Assist in digesting nucleic acids.

Q4b) Explain the process of absorption and transport of lipids in our body.

Ans) The process of absorption and transport of lipids in our body:

a) Emulsification and Digestion: Dietary lipids are emulsified by bile salts in the small intestine, forming small lipid droplets. Pancreatic lipase then breaks down these lipids into fatty acids and glycerol.

b) Formation of Micelles: Fatty acids and monoglycerides combine with bile salts to form micelles, which are small, water-soluble particles that can move through the watery environment of the small intestine.

c) Absorption: The micelles approach the surface of intestinal absorptive cells (enterocytes). Fatty acids and monoglycerides diffuse across the cell membrane into the enterocytes.

d) Incorporation into Chylomicrons: Inside the enterocytes, fatty acids and monoglycerides are reassembled into triglycerides. These triglycerides, along with cholesterol and fat-soluble vitamins, are packaged into lipoprotein particles called chylomicrons.

e) Transport through Lymphatic System: Chylomicrons are too large to enter the bloodstream directly, so they enter the lymphatic system through lacteals. They travel through lymphatic vessels to eventually enter the bloodstream at the thoracic duct near the heart.

f) Circulation: In the bloodstream, chylomicrons transport dietary lipids to various tissues, where they are either used for energy or stored in adipose tissue.

g) Lipoprotein Metabolism: Over time, chylomicrons lose triglycerides and become smaller. They are taken up by the liver, and their remnants are recycled.

Q5a) What is gluconeogenesis? Discuss the four substrates used in gluconeogenesis.

Ans) Gluconeogenesis is a metabolic pathway in the body that synthesizes glucose from non-carbohydrate precursors. It is vital for maintaining blood glucose levels during fasting or low-carbohydrate situations. Gluconeogenesis primarily occurs in the liver and, to a lesser extent, in the kidneys.

Four substrates used in gluconeogenesis are:

a) Lactate: Lactate is produced when muscles generate energy under anaerobic conditions. In the liver, lactate is converted back into pyruvate and then into glucose via gluconeogenesis.

b) Glycerol: Glycerol, released from triglycerides stored in adipose tissue, can be converted into glycerol-3-phosphate and further into glucose.

c) Amino Acids: Certain amino acids, particularly those that are glucogenic (can be converted into glucose), can serve as precursors. For example, alanine, which is produced in muscles, can be transported to the liver, and converted into glucose.

d) Propionate: Propionate, a product of the digestion of certain fatty acids, can be used in the synthesis of glucose.

Q5b) What is Phosphogluconate pathway? Give any three significance of this pathway.

Ans) The Phosphogluconate pathway, also known as the pentose phosphate pathway (PPP), is an alternative metabolic pathway that operates alongside glycolysis and has several significant functions:

Three key significance of the Phosphogluconate pathway are:

a) Production of NADPH: This pathway generates NADPH, a reduced form of nicotinamide adenine dinucleotide phosphate. NADPH is essential for biosynthetic reactions and plays a crucial role in protecting cells from oxidative damage by serving as a reducing agent.

b) Ribose-5-Phosphate Production: The PPP produces ribose-5-phosphate, a crucial precursor for the synthesis of nucleotides (the building blocks of DNA and RNA). This is particularly important during periods of rapid cell division and DNA replication.

c) Detoxification of Oxidative Stress: The pathway contributes to the detoxification of oxidative stress by generating NADPH, which supports the reduction of glutathione (an important antioxidant) and protects cells from damage caused by reactive oxygen species (ROS).

In summary, the Phosphogluconate pathway has a dual role in providing important cofactors like NADPH and essential substrates like ribose-5-phosphate, while also contributing to the cellular defense against oxidative stress.

Q6a) Write briefly the steps involved in cholesterol synthesis in the body.

Ans) Cholesterol is a vital lipid in the human body, serving as a structural component of cell membranes and a precursor for important molecules like steroid hormones. Cholesterol synthesis occurs mainly in the liver.

The key steps in cholesterol synthesis are as follows:

a) Acetyl-CoA Formation: The process begins with the formation of acetyl-CoA, which is derived from glucose metabolism or the breakdown of fatty acids.

b) HMG-CoA Formation: Acetyl-CoA is then converted into 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) through a series of enzymatic reactions.

c) Mevalonate Formation: HMG-CoA is transformed into mevalonate by the enzyme HMG-CoA reductase, which is a rate-limiting step in cholesterol synthesis.

d) Cholesterol Synthesis: Mevalonate undergoes several enzymatic reactions, ultimately leading to the formation of cholesterol.

Q6b) What do you understand by the term hyperproteinaemia.

Ans) Hyperproteinaemia refer to a group of medical conditions characterized by higher than normal levels of proteins in the blood. This can involve various types of proteins, such as immunoglobulins (antibodies), albumin, or other specific proteins. The term often relates to disorders that result in elevated levels of particular proteins.

For example, hyperproteinaemia can be categorized as:

a) Hypergammaglobulinemia: This condition is characterized by an excess of immunoglobulins (antibodies) in the blood and may indicate an overactive immune response, such as in autoimmune diseases or certain infections.

b) Hyperalbuminemia: Elevated levels of albumin, the most abundant protein in the blood, can be seen in conditions like dehydration or high-protein diets.

Hyperproteinaemia may result from various underlying medical conditions, including autoimmune disorders, infections, or certain malignancies. The specific treatment and implications of hyperproteinaemia depend on the cause and the type of proteins involved.

Q6c) Name three ketone bodies seen in ketosis.

Ans) Ketone Bodies in Ketosis: Ketosis is a metabolic state in which the body relies on the breakdown of fats for energy, leading to the production of ketone bodies.

Three primary ketone bodies associated with ketosis are:

a) Acetoacetate: Acetoacetate is one of the initial ketone bodies produced during the breakdown of fatty acids. It can be further converted into the other two major ketone bodies.

b) Beta-Hydroxybutyrate (BHB): BHB is the most abundant ketone body and serves as a major energy source for the body during ketosis. It is produced from acetoacetate and can be used by various tissues, including the brain.

c) Acetone: Acetone is a less abundant ketone body and is a breakdown product of acetoacetate. It is primarily exhaled or excreted in urine and is responsible for the characteristic "sweet" or fruity odour of the breath in individuals with uncontrolled diabetes or during prolonged fasting.

Ketosis typically occurs during fasting, very low-carbohydrate diets (like the ketogenic diet), or in uncontrolled diabetes. These ketone bodies provide an alternative energy source when glucose is limited, especially for the brain and other tissues.

Q7a) Explain the Urea cycle indicating the enzymes and co-enzymes involved in it.

Ans) The urea cycle, also known as the ornithine cycle, is a critical metabolic pathway in the liver that eliminates excess nitrogen from the body in the form of urea. This cycle prevents the toxic buildup of ammonia.

The key steps and enzymes involved are:

a) Carbamoyl Phosphate Synthesis: The cycle begins in the mitochondria, where carbamoyl phosphate is formed from ammonia and bicarbonate, catalyzed by carbamoyl phosphate synthetase I.

b) Citrulline Formation: Carbamoyl phosphate combines with ornithine, yielding citrulline in a reaction catalyzed by ornithine transcarbamylase.

c) Citrulline Transport: Citrulline is transported from the mitochondria to the cytoplasm.

d) Argininosuccinate Synthesis: In the cytoplasm, citrulline combines with aspartate to produce argininosuccinate, driven by the enzyme argininosuccinate synthase. This reaction also requires adenosine triphosphate (ATP).

e) Fumarate and Arginine Formation: Argininosuccinate is cleaved into fumarate and arginine by argininosuccinate lyase.

f) Urea Formation: Arginine undergoes hydrolysis, releasing urea and regenerating ornithine. This reaction is catalyzed by arginase.

Q7b) Explain the different ways by which non-essential amino acid is biosynthesised .

Ans) Non-essential amino acids can be synthesized by the body and do not need to be obtained from the diet.

There are different ways they are biosynthesized:

a) Transamination: Many non-essential amino acids are formed through transamination, a process where an amino group is transferred from one amino acid to a precursor molecule. For example, alanine is synthesized from pyruvate via transamination.

b) De Novo Synthesis: Some non-essential amino acids are formed de novo, meaning they are synthesized from scratch using precursor molecules. For instance, serine is produced from 3-phosphoglycerate, an intermediate in glycolysis.

c) Ammonium Ion Incorporation: Glutamine can donate its amine group in the biosynthesis of several non-essential amino acids. For example, glutamate is formed by incorporating ammonium ions into alpha-ketoglutarate.

d) Urea Cycle: Aspartate, a precursor for several non-essential amino acids like asparagine and arginine, is derived from the urea cycle.

The body maintains a balance between amino acid breakdown and biosynthesis to meet its needs, regulating the production of non-essential amino acids as necessary for various physiological processes.

Q8a) Describe the role of free radicals in lipid peroxidation.

Ans) Role of Free Radicals in Lipid Peroxidation:

Free radicals are highly reactive molecules with unpaired electrons, making them unstable and prone to stealing electrons from other molecules. In lipid peroxidation, free radicals play a detrimental role in damaging lipids, particularly the unsaturated fatty acids present in cell membranes.

The process can be summarized as follows:

a) Initiation: Free radicals, such as the hydroxyl radical (•OH) or peroxyl radical (•OOH), initiate lipid peroxidation by abstracting a hydrogen atom from an unsaturated fatty acid. This forms a lipid radical.

b) Propagation: The lipid radical reacts with molecular oxygen (O2), producing a lipid peroxyl radical (LOO•)

This radical, in turn, can attack adjacent lipids, creating a chain reaction. As the chain reaction continues, it generates more free radicals.

c) Termination: Antioxidants can terminate the chain reaction by neutralizing free radicals, preventing further lipid peroxidation. The presence of antioxidants helps protect cell membranes and other lipids from damage.

Lipid peroxidation can disrupt cell membranes, impair cellular functions, and lead to a range of health issues, including oxidative stress-related diseases.

Q8b) What are antioxidants? Give their classification and role in brief.

Ans) Antioxidants: Antioxidants are compounds that protect cells and biomolecules from the harmful effects of free radicals and oxidative stress. They work by neutralizing free radicals, thereby preventing cellular damage.

Antioxidants can be classified into enzymatic and non-enzymatic antioxidants.

a) Enzymatic Antioxidants:

Enzymatic antioxidants are proteins that include superoxide dismutase (SOD), catalase, and glutathione peroxidase. They catalyze reactions that convert harmful free radicals into less damaging substances.

b) Non-Enzymatic Antioxidants:

Non-enzymatic antioxidants are small molecules that include vitamins (e.g., vitamin C and vitamin E), minerals (e.g., selenium), and phytochemicals (e.g., flavonoids and polyphenols). They directly interact with free radicals, neutralizing them. For example, vitamin C can donate electrons to free radicals, rendering them harmless.

The role of antioxidants is to:

a) Prevent oxidative damage to cellular components, including lipids, proteins, and DNA.

b) Protect against various diseases associated with oxidative stress, such as cancer, cardiovascular diseases, and neurodegenerative disorders.

c) Support the body's natural defense mechanisms against free radicals.

Q9a) Indicate the steps involved in formation of vitamin D3.

Ans) The formation of vitamin D3, also known as cholecalciferol, is a multi-step process primarily initiated in the skin when it is exposed to ultraviolet B (UVB) sunlight. Here are the key steps involved:

a) UVB Exposure: The process begins when 7-dehydrocholesterol, a compound naturally present in the skin, absorbs UVB radiation from sunlight. This UVB exposure causes a structural change in 7-dehydrocholesterol, converting it into pre-vitamin D3.

b) Thermal Isomerization: Pre-vitamin D3 is not biologically active. It undergoes a thermal isomerization process, which is a rearrangement of its chemical structure. This step is temperature-dependent and occurs at body temperature.

c) Formation of Vitamin D3: The thermal isomerization results in the formation of vitamin D3 (cholecalciferol), which is now biologically active.

d) Transport to the Liver: Vitamin D3 is then transported to the liver, where it undergoes hydroxylation (addition of a hydroxyl group) at the 25th carbon position. This forms 25-hydroxyvitamin D3 (calcifediol or calcidiol).

e) Transport to the Kidneys: Calcifediol is further transported to the kidneys, where it undergoes a second hydroxylation, this time at the 1st carbon position. This forms the active form of vitamin D, 1,25-dihydroxyvitamin D3 (calcitriol).

Q9b) Why minerals are essential for us? Give the biochemical role of zinc in our body.

Ans) Minerals are inorganic nutrients that are essential for various physiological functions in the human body. They play a crucial role in maintaining overall health and well-being.

These are some key reasons why minerals are essential for us:

a) Structural Components: Minerals are integral components of body structures. For example, calcium and phosphorus are essential for bone and teeth formation.

b) Electrolyte Balance: Minerals like sodium, potassium, and chloride help regulate electrolyte balance in the body, which is vital for nerve function, muscle contractions, and maintaining fluid balance.

c) Cofactors: Many minerals act as cofactors for enzymes, facilitating various biochemical reactions. For instance, magnesium is involved in over 300 enzyme reactions, including those related to energy metabolism.

d) Nerve Function: Minerals such as calcium, sodium, and potassium are crucial for transmitting nerve impulses, allowing communication between different parts of the nervous system.

Biochemical Role of Zinc:

a) Enzyme Cofactor: Zinc serves as a cofactor for numerous enzymes involved in various metabolic processes, including DNA synthesis, protein digestion, and wound healing.

b) Immune Function: Zinc is crucial for proper immune system function. It is involved in the development and function of immune cells, and a deficiency can impair the body's ability to fight infections.

c) Growth and Development: Zinc plays a role in growth, development, and the maintenance of healthy tissues. It is especially important during pregnancy, infancy, and adolescence.

d) Gene Expression: Zinc is involved in gene expression, helping regulate the transcription of genetic information.

Q10a) What do you understand by the term “inborn errors of metabolism”?

Ans) Inborn Errors of Metabolism, often referred to as IEM, represent a group of rare genetic disorders that affect the body's ability to process and convert nutrients from food into energy or perform essential biochemical reactions. These conditions result from mutations in specific genes responsible for encoding enzymes or proteins vital for metabolic pathways.

Key characteristics of IEM include:

a) Genetic Origin: IEM are hereditary conditions caused by mutations in specific genes. These mutations may be inherited from parents or occur spontaneously.

b) Enzyme Deficiency: In most cases, IEM are characterized by a deficiency or complete absence of a specific enzyme required for a metabolic pathway. Without the enzyme, the body cannot effectively metabolize certain substances.

c) Broad Spectrum: IEM encompass a wide range of disorders, each associated with a distinct metabolic pathway. Examples include phenylketonuria (PKU), maple syrup urine disease, and homocystinuria.

d) Variable Severity: The severity of IEM can vary significantly. Some individuals may exhibit severe symptoms from birth, while others may experience milder symptoms later in life.

e) Clinical Presentation: Symptoms of IEM can affect various body systems and organs, leading to a wide range of clinical presentations, including developmental delays, intellectual disabilities, seizures, metabolic crises, and organ dysfunction.

f) Management: The treatment of IEM often involves dietary restrictions, enzyme replacement therapies, medications, and supportive care to manage symptoms and prevent metabolic crises.

Q10b) Differentiate between Group I and Group II hormones, giving examples.

Ans) Comparison between Group I and Group II,

Section B - OTQ (Objective Type Questions)

Q1) Explain the following in 2-3 sentences. Also give the structure wherever possible.

Q1a) Isomer

Ans) Isomers are molecules with the same molecular formula but different structural arrangements or spatial orientation. For example, glucose and fructose are isomers because they both have the molecular formula C6H12O6 but differ in their structural arrangement.

Q1b) Essential fatty acids

Ans) Essential fatty acids are fats that the human body cannot synthesize and must be obtained through the diet. Two well-known essential fatty acids are linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid).

Q1c) Isoprene

Ans) Isoprene is a common structural unit found in various natural compounds, including natural rubber. It has the molecular formula C5H8 and serves as the building block for the formation of compounds like terpenes.

Q1d) Turnover number

Ans) The turnover number, also known as kcat, is a parameter in enzyme kinetics. It represents the number of substrate molecules converted to product by one enzyme molecule per unit time under optimal conditions. It is a measure of the enzyme's catalytic efficiency.

Q1e) Brush border

Ans) The brush border refers to the microvilli-covered surface of certain cells, particularly in the small intestine and kidney. These microvilli increase the surface area for absorption and secretion, facilitating nutrient absorption and waste elimination.

Q1f) Electron Transport Chain

Ans) The electron transport chain is a series of protein complexes embedded in the inner mitochondrial membrane. It plays a crucial role in cellular respiration by transferring electrons and generating a proton gradient used to produce ATP.

Q1g) Ketosis

Ans) Ketosis is a metabolic state in which the body predominantly uses ketone bodies as an alternative energy source, typically when there is a shortage of carbohydrates. It occurs during fasting, low-carbohydrate diets, or in certain medical conditions.

Q1h) Metallo flavoproteins

Ans) Metallo flavoproteins are a group of enzymes or proteins that contain flavin (e.g., flavin mononucleotide, FMN, or flavin adenine dinucleotide, FAD) and a metal cofactor. These proteins play various roles in biological redox reactions.

Q1i) Transcription

Ans) Transcription is the process of synthesizing RNA from a DNA template. It is a critical step in gene expression, during which the genetic information in DNA is transcribed into a complementary RNA molecule, such as messenger RNA (mRNA).

Q1j) Allosteric mechanisms

Ans) Allosteric mechanisms involve the regulation of enzyme activity through the binding of a molecule at a site other than the enzyme's active site. This binding can either enhance (positive allosteric regulation) or inhibit (negative allosteric regulation) the enzyme's activity, affecting its function and affinity for substrates.

Q2) Name the defective enzyme in the following diseases:

Q2a) Alcaptonuria

Ans) The defective enzyme in alcaptonuria is homogentisate 1,2-dioxygenase.

Q2b) Gaucher’s disease

Ans) Gaucher's disease is caused by a deficiency of the enzyme beta-glucocerebrosidase.

Q2c) Homocystinuria

Ans) Homocystinuria results from the deficiency of enzymes involved in the metabolism of homocysteine. One of the enzymes that can be affected is cystathionine beta-synthase.

Q2d) Pentosuria

Ans) Pentosuria is associated with a deficiency of the enzyme L-xylulose reductase.

Q2e) Albinism

Ans) Albinism can result from various genetic mutations, but it is not associated with a single specific defective enzyme. Instead, it is characterized by a lack of melanin production due to a variety of genetic mutations affecting enzymes involved in melanin synthesis.

Q3) Match the items in List I with items in List II :

Ans)