All Free Biology MCQs with Answers

1431. Which one gives blue colour with iodine_______________?

• A. Starch
• B. Glycogen
• C. Cellulose
• D. Polysaccharide

Explanation: Iodine forms a blue to blue-black complex with the helical structure of amylose in starch. Students may choose glycogen because it is also a polysaccharide, but glycogen gives a reddish-brown colour with iodine rather than the characteristic blue colour of starch.

1432. Which of the following polysaccharide is called animal starch_________________?

• A. Starch
• B. Glycogen
• C. Cellulose
• D. None of these

Explanation: Glycogen is called animal starch because it is the main storage polysaccharide in animals, especially in liver and muscles. Students may choose starch because both molecules store glucose, but starch is the corresponding storage polysaccharide in plants.

1433. The covalent bond between two monosaccharide subunits is called________________?

• A. Phosphodiester bond
• B. Peptide bond
• C. Glycosidic Bond
• D. Ionic bond

Explanation: A glycosidic bond joins two monosaccharides through a condensation reaction, in which a water molecule is removed. Students may choose a peptide bond because it also joins biological subunits, but peptide bonds link amino acids, not sugars.

1434. Which one is soluble in hot water_____________?

• A. Starch
• B. Glycogen
• C. Amylose
• D. Amylopectin.

Explanation: Amylose, the mostly unbranched component of starch, can dissolve in hot water and forms a colloidal solution. Students may choose amylopectin because it is also a component of starch, but its extensive branching makes it much less soluble in hot water than amylose.

1435. Which of the following carbohydrate can not be hydrolysed__________________?

• A. Monosaccharide
• B. Oligosaccharide
• C. Polysaccharide
• D. None of these

Explanation: A monosaccharide is already a single sugar unit, so it cannot be hydrolysed into smaller carbohydrates. Students may choose an oligosaccharide, but oligosaccharides contain several monosaccharide units joined by bonds that can be hydrolysed.

1436. ____________% of Glucose normally present in our blood is?

• A. 0.80%
• B. 0.08%
• C. 1.80%
• D. 8%

Explanation: Normal blood glucose is about 80 mg per 100 mL, which is 0.08 g per 100 mL, or approximately 0.08%. The likely mistake is choosing 0.80%, which is ten times higher than the usual blood glucose concentration.

1437. Starch cellulose and glaycogen yield ___________ on complete hydrolysis?

• A. Maltose
• B. Sucrose
• C. Fructose
• D. Glucose

Explanation: Starch, cellulose and glycogen are polysaccharides made from repeating glucose units, so complete hydrolysis releases glucose. Maltose may be produced during partial starch breakdown, but it is not the final product of complete hydrolysis.

1438. Ribose is an example of___________?

• A. Trioses
• B. Tetroses
• C. Pentose
• D. Hexose

Explanation: Ribose contains five carbon atoms, making it a pentose sugar. The common mistake is choosing hexose by confusing ribose with glucose or fructose, both of which contain six carbon atoms.

1439. Which one are most complex sugar_____________?

• A. Monosaccharides
• B. Oligosaccharides
• C. Polysaccharides
• D. None of these

Explanation: Polysaccharides are the most complex carbohydrates because they contain long chains of many monosaccharide units. Oligosaccharides are a tempting choice, but they contain only a small number of sugar units and are less complex.

1440. A complex substance which on hydrolysis yields polyhydroxy aldehyde or ketone subunits is called__________?

• A. Lipid
• B. Carbohydrate
• C. Protein
• D. Carotein

Explanation: Carbohydrates are polyhydroxy aldehydes or ketones, or substances that yield these compounds on hydrolysis. Protein is the likely alternative because it also forms complex biological substances, but proteins hydrolyse into amino acids rather than sugar units.