Question 1

A triose sugar is?

Accepted Answer

Answer reason: A triose contains three carbons; glycerose (glyceraldehyde) is a triose, whereas ribose is a pentose, erythrose is a tetrose, and fructose is a hexose.

Question 2

Polysaccharides are?

Accepted Answer

Answer reason: Polysaccharides are macromolecules formed by the polymerization of many monosaccharide units, making them polymers; they are neither acids, proteins, nor oils.

Question 3

The number of double bonds in arachidonic acid is?

Accepted Answer

Answer reason: Arachidonic acid is a 20:4 polyunsaturated fatty acid (5,8,11,14) containing four double bonds.

Question 4

Creatinuria is caused by the deficiency of vitamin?

Accepted Answer

Answer reason: Vitamin E deficiency leads to muscle degeneration, with increased urinary excretion of creatine (creatinuria).

Question 5

The most active site of protein synthesis is the?

Accepted Answer

Answer reason: Ribosomes are cellular organelles that translate mRNA into polypeptides, making them the primary sites of protein synthesis.

Question 6

Maltose can be formed by the hydrolysis of?

Accepted Answer

Answer reason: Starch, dextrins, and glycogen are alpha-1,4-linked glucose polymers; their hydrolysis yields maltose units.

Question 7

An example of a saturated fatty acid is?

Accepted Answer

Answer reason: Palmitic acid has no double bonds and is saturated. Oleic and erucic acids are monounsaturated, and linoleic acid is polyunsaturated.

Question 8

Dietary fats, after absorption, appear in the circulation as?

Accepted Answer

Answer reason: Enterocytes package absorbed dietary triglycerides into chylomicrons, which enter the lymph and then the blood; HDL, VLDL, and LDL are primarily liver-derived or metabolic products.

Question 9

A polysaccharide that is often called animal starch is?

Accepted Answer

Answer reason: Glycogen is the storage polysaccharide in animals and is commonly referred to as animal starch.

Question 10

In polysaccharides, monosaccharides are joined by?

Accepted Answer

Answer reason: Monosaccharides are linked through glycosidic bonds (O-glycosidic linkages) to form polysaccharides; the other options are incorrect or nonspecific.

Question 11

Glycogen is stored in the liver and...?

Accepted Answer

Answer reason: Glycogen is primarily stored in the liver and skeletal muscle; bones, kidneys, and joints are not major glycogen stores.

Question 12

Cholesterol is a precursor in the biogenesis of?

Accepted Answer

Answer reason: Cholesterol (via 7-dehydrocholesterol in the skin) is the precursor of cholecalciferol (vitamin D3), which is formed after UV exposure.

Question 13

What color indicates a positive result in Benedict's test?

Accepted Answer

Answer reason: In Benedict’s test for reducing sugars, increasing positivity progresses from green (+) to yellow (++) to orange (+++) to brick-red (++++). Thus +++ corresponds to orange.

Question 14

The cell membrane is selectively permeable due to?

Accepted Answer

Answer reason: Integral membrane proteins (channels and carriers) confer specificity by allowing only certain solutes to pass, making the membrane selectively permeable. Cholesterol modulates fluidity; the phospholipid bilayer provides a barrier but not selectivity; enzymes are not primarily responsible.

Question 15

A Haworth projection is a common way to represent the cyclic structure of monosaccharides from a simple three-dimensional perspective?

Accepted Answer

Answer reason: Haworth projections are standard depictions of cyclic monosaccharides, conveying a simple 3D perspective of ring structures.

Question 16

When ATP forms AMP?

Accepted Answer

Answer reason: ATP can be cleaved to AMP with release of inorganic pyrophosphate (PPi), which is typical of ligase reactions; energy is released, not zero.

Question 17

Which molecule is oxidized in the conversion of glucose and oxygen to carbon dioxide and water?

Accepted Answer

Answer reason: During cellular respiration, glucose loses electrons/hydrogen and is converted to CO2 (oxidation), while oxygen gains electrons to form water (reduction).

Question 18

Which mechanism in phototherapy is responsible for the reduction in serum bilirubin?

Accepted Answer

Answer reason: Phototherapy decreases bilirubin through multiple photochemical pathways: configurational isomerization, structural isomerization to lumirubin, and photo-oxidation; thus all apply.

Question 19

A vitamin that functions like a steroid hormone?

Accepted Answer

Answer reason: Vitamin D (calcitriol) is a secosteroid that binds a nuclear receptor and regulates gene transcription, functioning like a steroid hormone.

Question 20

Proteins can be used for gluconeogenesis under what conditions-?

Accepted Answer

Answer reason: When carbohydrate intake is low, the body increases gluconeogenesis and uses amino acids from proteins to produce glucose; high carbs or high calories suppress this, and low protein limits substrate.

Question 21

__________ contains a triple bond?

Accepted Answer

Answer reason: Alkynes are hydrocarbons characterized by at least one carbon–carbon triple bond; alkanes have single bonds and alkenes have double bonds, so only alkynes fit.

Question 22

Strands of DNA are held together by?

Accepted Answer

Answer reason: Complementary DNA strands pair via hydrogen bonds between bases (A–T, G–C). Covalent bonds form the sugar-phosphate backbone, not interstrand pairing; ionic and dipole-dipole are incorrect.

Question 23

Non-proteinaceous part of holoenzyme is?

Accepted Answer

Answer reason: A holoenzyme consists of an apoenzyme (protein part) plus a cofactor (non-protein part). Therefore, the non-proteinaceous component is the cofactor. A prosthetic group is a tightly bound type of cofactor; apoenzyme is protein, and tubulin is unrelated.

Question 24

An essential agent for converting glucose to glycogen in liver is?

Accepted Answer

Answer reason: Glycogen synthesis requires activation of glucose-1-phosphate to UDP-glucose, which uses UTP; GTP, lactic acid, and pyruvic acid are not required for this step.

Question 25

The aldose sugar is?

Accepted Answer

Answer reason: Glycerose (glyceraldehyde) is an aldotriose containing an aldehyde group. Ribulose, erythrulose, and dihydoxyacetone are ketoses.

Question 26

A sugar alcohol is?

Accepted Answer

Answer reason: Mannitol is a polyol (sugar alcohol). Trehalose is a disaccharide, while xylulose and arabinose are sugars, not alcohols.

Question 27

An example of polar amino acid is?

Accepted Answer

Answer reason: Arginine has a positively charged (basic) guanidinium side chain and is polar; alanine, leucine, and valine are nonpolar aliphatic amino acids.

Question 28

A ketogenic amino acid is?

Accepted Answer

Answer reason: Leucine is a purely ketogenic amino acid; valine and cysteine are glucogenic, and threonine is both glucogenic and ketogenic.

Question 29

An example of scleroprotein is?

Accepted Answer

Answer reason: Scleroproteins are fibrous proteins such as keratin, collagen, and elastin. Zein and glutenin are plant storage proteins and ovoglobulin is a globular protein.

Question 30

A polysaccharide which is often called animal starch is?

Accepted Answer

Answer reason: Glycogen is the storage polysaccharide in animals and is commonly termed animal starch; starch is the plant storage polysaccharide, while inulin and dextrin are different carbohydrates.

Question 31

The enzymes of β-oxidation are found in?

Accepted Answer

Answer reason: Fatty acid β-oxidation primarily occurs in the mitochondrial matrix where its enzymes are located; peroxisomes participate for very-long-chain FAs, but the standard answer is mitochondria.

Question 32

The sugar moiety present in DNA is?

Accepted Answer

Answer reason: DNA contains the pentose sugar 2'-deoxyribose; ribose is found in RNA and lyxose is not a component of nucleic acids.

Question 33

Cell membrane is mainly made up for .......?

Accepted Answer

Answer reason: The plasma membrane primarily consists of a phospholipid bilayer; proteins and carbohydrates are lesser components.

Question 34

Lactose is made up of glucose and .....?

Accepted Answer

Answer reason: Lactose is the disaccharide composed of glucose and galactose.

Question 35

Maltose is made up of .......... And glucose?

Accepted Answer

Answer reason: Maltose is a disaccharide composed of two glucose molecules (α-1,4 linkage), so the other unit is glucose.

Question 36

All of the following are globular protein except?

Accepted Answer

Answer reason: Silk fibroin is a fibrous protein, not a globular protein. ALT and AST are enzymes (globular), and albumin is a classic globular protein.

Question 37

The main product of protein metabolism is _?

Accepted Answer

Answer reason: Amino acid catabolism generates ammonia which is converted in the liver to urea—the principal nitrogenous waste product. Iodine is a micronutrient, and glycogen is a carbohydrate storage form.

Question 38

Which one of the following statements concerning glucose metabolism is correct...?

Accepted Answer

Answer reason: Pyruvate kinase catalyzes the essentially irreversible step converting PEP to pyruvate in glycolysis. (a) is false—lactate is produced in many tissues, not only RBCs. (b) is false—most cells use facilitative GLUT transporters, not Na+-glucose cotransport. (d) is false—insulin increases hepatic fructose-2,6-bisphosphate, stimulating glycolysis.

Question 39

Why is glycolysis considered one of the first metabolic pathways to have evolved?

Accepted Answer

Answer reason: Glycolysis is common to almost all organisms, occurs in the cytosol without organelles, and proceeds anaerobically—features consistent with early life before atmospheric oxygen.

Question 40

Cyanide is a poison that blocks the passage of electrons along the ETC. Which of the following is a metabolic effect of this poison?

Accepted Answer

Answer reason: Cyanide inhibits cytochrome c oxidase (Complex IV), halting electron flow and proton pumping. Without the proton gradient, ATP synthase cannot function, so oxidative phosphorylation stops.

Question 41

The synthesis of glucose from pyruvate by gluconeogenesis?

Accepted Answer

Answer reason: Conversion of pyruvate to oxaloacetate in gluconeogenesis uses pyruvate carboxylase, a biotin-dependent enzyme. The pathway is not exclusively cytosolic and does not require FAD.

Question 42

What best describes amylose?

Accepted Answer

Answer reason: Amylose is a linear polysaccharide of D-glucose linked by alpha(1→4) bonds; branching with alpha(1→6) occurs in amylopectin, and beta linkages characterize cellulose.

Question 43

What is the role of oxygen in cellular respiration?

Accepted Answer

Answer reason: In aerobic respiration, O2 accepts electrons at the end of the electron transport chain and is reduced to water, enabling oxidative phosphorylation. It is not involved in glycolysis, does not donate electrons, and does not supply activation energy.

Question 44

Which of the following reactions is incorrectly paired with its location?

Accepted Answer

Answer reason: The citric acid (Krebs) cycle occurs in the mitochondrial matrix, not on the cristae (inner membrane folds). The other pairings are correct.

Question 45

Which statement is correct about cholesterol?

Accepted Answer

Answer reason: Cholesterol is the precursor for all steroid hormones, is required for bile acid/salt synthesis, and is a key structural component of cell membranes; therefore all statements are correct.

Question 46

Which mechanism in phototherapy is chiefly responsible for reduction in serum bilirubin?

Accepted Answer

Answer reason: Phototherapy rapidly lowers serum unconjugated bilirubin primarily via photoisomerization (configurational isomers), which causes an early and significant fall in measured bilirubin; structural isomerization and photo-oxidation contribute less.

Question 47

Rancidity of fat is due to which of the following?

Accepted Answer

Answer reason: Rancidity of fats results from oxidative spoilage—autoxidation of unsaturated fatty acids. Hydrogenation saturates double bonds and protects against rancidity; microbial growth is a different type of spoilage.

Question 48

The pentose sugar present mainly in the heart muscle is...?

Accepted Answer

Answer reason: Lyxose is a rare aldopentose reported in mammalian heart muscle, whereas ribose is ubiquitous in nucleic acids and arabinose/xylose are primarily plant sugars.

Question 49

Compounds having the same structural formula but differing in spatial configuration are known as.....?

Accepted Answer

Answer reason: Stereoisomers have the same structural formula but differ in the three-dimensional arrangement of atoms. Anomers, optical isomers, and epimers are specific types of stereoisomers.

Question 50

What is the catabolic reaction of proteins that produces energy called?

Accepted Answer

Answer reason: Protein catabolism for energy involves removal of the amino group (deamination), leaving a carbon skeleton that enters the TCA cycle. Transamination is amino group transfer, beta oxidation is fatty acid catabolism, and oxidative phosphorylation is the final ATP-generating step for many substrates, not specific to proteins.

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