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1. Carbohydrates that cannot be hydrolyzed further into simpler polyhydroxy compounds are called:
A. Monosaccharides
B. Disaccharides
C. Polysaccharides
D. Oligosaccharides
Answer: A. Monosaccharides
Explanation: Monosaccharides such as glucose and fructose are the simplest carbohydrate units and cannot be broken down further by hydrolysis.
2. In which disaccharide are glucose and fructose linked together through a glycosidic bond?
A. Sucrose
B. Maltose
C. Lactose
D. Starch
Answer: A. Sucrose
Explanation: Sucrose is formed by the glycosidic linkage between the C1 of glucose and C2 of fructose.
3. Proteins are essentially polymers built from monomer units of:
A. Amino acids
B. Glucose units
C. Fatty acids
D. Nucleotides
Answer: A. Amino acids
Explanation: Proteins are polypeptides formed by condensation polymerization of various amino acids linked by peptide bonds.
4. The secondary structure of a protein mainly refers to:
A. Regular structural patterns such as the α-helix and β-pleated sheet
B. The linear sequence of amino acids
C. The overall three-dimensional folding of the whole chain
D. The aggregation of multiple protein subunits
Answer: A. Regular structural patterns such as the α-helix and β-pleated sheet
Explanation: Secondary structure describes local, regular folding patterns of the polypeptide backbone stabilized by hydrogen bonds.
5. Denaturation of a protein primarily leads to the loss of its:
A. Biological activity, due to disruption of secondary and tertiary structure
B. Primary structure (amino acid sequence)
C. Molecular formula
D. Amino acid composition
Answer: A. Biological activity, due to disruption of secondary and tertiary structure
Explanation: Denaturing agents disrupt hydrogen bonds and other interactions that maintain higher-order structure, without breaking the peptide bonds of the primary structure.
6. A key structural difference between DNA and RNA is that DNA contains the sugar:
A. Deoxyribose
B. Ribose
C. Glucose
D. Fructose
Answer: A. Deoxyribose
Explanation: DNA contains 2-deoxyribose (lacking an oxygen at the 2' position), whereas RNA contains ribose.
7. Which nitrogenous base is found in DNA but is replaced by a different base in RNA?
A. Thymine
B. Cytosine
C. Adenine
D. Guanine
Answer: A. Thymine
Explanation: DNA contains thymine, while RNA contains uracil in its place.
8. A deficiency of which vitamin causes the disease scurvy?
A. Vitamin C
B. Vitamin A
C. Vitamin D
D. Vitamin B12
Answer: A. Vitamin C
Explanation: Scurvy, characterized by bleeding gums and poor wound healing, results from a deficiency of vitamin C (ascorbic acid).
9. Enzymes are best described as:
A. Biological catalysts, mostly made of protein
B. Simple carbohydrates
C. Nucleic acids
D. Lipid molecules
Answer: A. Biological catalysts, mostly made of protein
Explanation: Enzymes are typically globular proteins that catalyze specific biochemical reactions by lowering activation energy.
10. The zwitterionic form of an amino acid arises because it contains:
A. Both a basic -NH2 group and an acidic -COOH group
B. Only a -COOH group
C. Only an -NH2 group
D. No ionizable functional groups
Answer: A. Both a basic -NH2 group and an acidic -COOH group
Explanation: In aqueous solution, the -COOH group donates a proton to the -NH2 group, forming an internal salt (zwitterion) with both positive and negative charges.
11. Amino acids are joined together in a protein chain through:
A. Peptide bonds
B. Glycosidic bonds
C. Phosphodiester bonds
D. Hydrogen bonds alone
Answer: A. Peptide bonds
Explanation: A peptide bond forms between the -COOH group of one amino acid and the -NH2 group of the next, with loss of a water molecule.
12. Insulin, which regulates blood glucose levels, is an example of a:
A. Protein hormone
B. Carbohydrate
C. Nucleic acid
D. Vitamin
Answer: A. Protein hormone
Explanation: Insulin is a small protein hormone composed of two polypeptide chains linked by disulfide bonds.
This page contains a chapter-wise objective practice set. Try the questions without checking the answer first, then use the explanation to understand the point you missed. The current page contains 12 questions, so you can practise in smaller sets when you are revising.
Quick revision tip
After the practice set, write down the question numbers you missed and revise only those concepts once more. This makes MCQ practice more useful than repeatedly attempting the same questions without reviewing mistakes.
