In the non-oxidative phase of the pentose phosphate pathway, transketolase requires which cofactor?

The correct answer is C: Thiamine pyrophosphate (TPP). Transketolase requires thiamine pyrophosphate (TPP/vitamin B1) as a cofactor to transfer 2-carbon ketol groups between sugar phosphates in the non-oxidative phase of the pentose phosphate pathway.

A protein with multiple subunits shows cooperative binding of substrate. This phenomenon is best explained by:

The correct answer is B: Allosteric regulation. Cooperative binding (positive cooperativity) occurs when binding of one substrate molecule increases affinity for subsequent molecules, a classic example of allosteric regulation as seen in hemoglobin.

What is the primary difference between competitive and non-competitive enzyme inhibition in terms of Vmax and Km?

The correct answer is B: Competitive inhibition increases Km without affecting Vmax; non-competitive inhibition decreases Vmax. Competitive inhibitors compete with substrate for the active site, increasing apparent Km while Vmax remains unchanged. Non-competitive inhibitors bind to a site other than the active site, decreasing Vmax without changing Km.

Which of the following amino acids is NOT classified as a standard protein amino acid?

The correct answer is A: Selenocysteine. Selenocysteine is the 21st amino acid and is not among the standard 20 protein amino acids. It contains selenium instead of sulfur.

Which of the following is a consequence of excessive cholesterol accumulation in arteries?

The correct answer is B: Formation of atherosclerotic plaques causing narrowing of arteries. High cholesterol, particularly LDL cholesterol, can accumulate in artery walls forming atherosclerotic plaques, leading to arterial narrowing (atherosclerosis) and increased risk of heart disease.

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Biochemistry
Carbohydrates

Metabolic pathways, enzymes, proteins

26 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–26 of 26

Topics in Biochemistry

All Proteins & Enzymes 100 Carbohydrates 100 Lipids 78

Q.21 Easy Carbohydrates

Which carbohydrate classification includes both monosaccharides and oligosaccharides?

A Polysaccharides

B Simple carbohydrates

C Complex carbohydrates

D Reducing sugars

Correct Answer: B. Simple carbohydrates

EXPLANATION

Simple carbohydrates include monosaccharides (glucose, fructose, galactose) and oligosaccharides (2-10 units like sucrose, maltose, lactose). Complex carbohydrates are polysaccharides with >10 units (starch, glycogen, cellulose).

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Q.22 Easy Carbohydrates

Sucrose is composed of which two monosaccharides?

A Glucose + Galactose

B Glucose + Fructose

C Glucose + Glucose

D Galactose + Fructose

Correct Answer: B. Glucose + Fructose

EXPLANATION

Sucrose (table sugar) is a disaccharide composed of one glucose and one fructose unit linked by an α(1→2) glycosidic bond. It is a non-reducing sugar.

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Q.23 Easy Carbohydrates

Which enzyme catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate?

A Phosphofructokinase

B Phosphoglucose isomerase

C Hexokinase

D Aldolase

Correct Answer: B. Phosphoglucose isomerase

EXPLANATION

Phosphoglucose isomerase (PGI) catalyzes the reversible conversion of glucose-6-phosphate to fructose-6-phosphate in glycolysis, step 2.

Test

Q.24 Easy Carbohydrates

What is the glycosidic linkage present in maltose?

A α(1→4) glycosidic bond

B β(1→4) glycosidic bond

C α(1→6) glycosidic bond

D β(1→6) glycosidic bond

Correct Answer: A. α(1→4) glycosidic bond

EXPLANATION

Maltose consists of two glucose units linked by an α(1→4) glycosidic bond. This is a reducing disaccharide formed during starch digestion.

Test

Q.25 Easy Carbohydrates

Glycogen is primarily stored in which of the following tissues in humans?

A Adipose tissue and brain

B Liver and skeletal muscles

C Pancreas and kidneys

D Heart and lungs

Correct Answer: B. Liver and skeletal muscles

EXPLANATION

Glycogen, the storage polysaccharide in animals, is primarily stored in the liver (100-120g) and skeletal muscles (400-500g). The liver glycogen maintains blood glucose, while muscle glycogen is used locally.

Test

Q.26 Easy Carbohydrates

Which of the following is a pentose sugar found in RNA?

A Ribose

B Deoxyribose

C Glucose

D Fructose

Correct Answer: A. Ribose

EXPLANATION

Ribose is a pentose sugar (5-carbon sugar) that is a component of RNA. Deoxyribose is found in DNA, while glucose and fructose are hexose sugars.

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