Introduction to biomolecules MCQs With Answer

Introduction to biomolecules MCQs With Answer is a focused study tool for B. Pharm students preparing for pharmacology, biochemistry and pharmacy exams. Covering essential biomolecules — carbohydrates, proteins, lipids, nucleic acids, amino acids, vitamins and enzymes — the MCQs emphasize structure, function, bonding, metabolism and clinical relevance. Each question is paired with precise answers to reinforce concepts like peptide and glycosidic bonds, stereochemistry, isoelectric point, fatty acid saturation, nucleotide composition and enzyme kinetics. Ideal for quick revision, self-assessment and classroom practice, this resource helps build conceptual clarity and exam confidence. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which covalent bond links amino acids in a polypeptide chain?

• Glycosidic bond
• Peptide bond
• Phosphodiester bond
• Hydrogen bond

Correct Answer: Peptide bond

Q2. Which monosaccharide is the normal circulating sugar measured in blood glucose tests?

• Fructose
• Galactose
• Glucose
• Mannose

Correct Answer: Glucose

Q3. The primary structure of a protein refers to:

• Its three-dimensional folding
• The sequence of amino acids
• The arrangement of subunits
• Its pattern of hydrogen bonding

Correct Answer: The sequence of amino acids

Q4. Which fatty acid feature increases membrane fluidity at physiological temperatures?

• High saturation
• Long chain length
• Trans double bonds
• Cis double bonds

Correct Answer: Cis double bonds

Q5. Which nucleotide base is a purine found in DNA?

• Uracil
• Adenine
• Cytosine
• Thymidine

Correct Answer: Adenine

Q6. Which vitamin is essential as a coenzyme in carboxylation reactions (biotin-dependent)?

• Thiamine (B1)
• Riboflavin (B2)
• Niacin (B3)
• Biotin (B7)

Correct Answer: Biotin (B7)

Q7. The isoelectric point (pI) of an amino acid is defined as:

• The pH at which net charge is zero
• The pH of maximum solubility
• The pH at which it denatures
• The pH where it has maximum positive charge

Correct Answer: The pH at which net charge is zero

Q8. Which bond joins monosaccharide units in glycogen?

• β-1,4-glycosidic bond
• α-1,4-glycosidic bond
• Peptide bond
• Phosphodiester bond

Correct Answer: α-1,4-glycosidic bond

Q9. Enzyme kinetics parameter Km represents:

• The maximum velocity
• The substrate concentration at half Vmax
• The turnover number
• The enzyme concentration

Correct Answer: The substrate concentration at half Vmax

Q10. Which amino acid has a thiol group that can form disulfide bonds?

• Serine
• Methionine
• Cysteine
• Alanine

Correct Answer: Cysteine

Q11. Which lipid class is a major component of cell membranes and contains glycerol, two fatty acids and a phosphate group?

• Steroid
• Triglyceride
• Phospholipid
• Glycolipid

Correct Answer: Phospholipid

Q12. What type of interaction stabilizes an alpha-helix secondary structure?

• Disulfide bridges
• Hydrophobic interactions between side chains
• Hydrogen bonds between backbone carbonyl and amide groups
• Ionic bonds between side chains

Correct Answer: Hydrogen bonds between backbone carbonyl and amide groups

Q13. Which sugar is a component of RNA but not DNA?

• Deoxyribose
• Ribose
• Glucose
• Fructose

Correct Answer: Ribose

Q14. A competitive enzyme inhibitor most directly affects which kinetic parameter?

• Decreases Vmax
• Increases Vmax
• Increases apparent Km
• Decreases Km

Correct Answer: Increases apparent Km

Q15. Which amino acid is positively charged at physiological pH?

• Aspartic acid
• Glutamic acid
• Lysine
• Serine

Correct Answer: Lysine

Q16. Which technique is commonly used to determine primary sequence of a small peptide?

• X-ray crystallography
• Edman degradation
• UV–visible spectroscopy
• NMR imaging

Correct Answer: Edman degradation

Q17. Which disaccharide is composed of glucose and fructose?

• Lactose
• Maltose
• Sucrose
• Cellobiose

Correct Answer: Sucrose

Q18. In nucleic acids, phosphodiester bonds link:

• Sugar to base
• Base to base
• Sugar–phosphate backbone between nucleotides
• Amino acids together

Correct Answer: Sugar–phosphate backbone between nucleotides

Q19. Which essential amino acid must be obtained from the diet and is aromatic?

• Leucine
• Phenylalanine
• Proline
• Glycine

Correct Answer: Phenylalanine

Q20. Which vitamin acts as a precursor for NAD+ and NADP+?

• Vitamin B3 (Niacin)
• Vitamin B6 (Pyridoxine)
• Vitamin C (Ascorbic acid)
• Vitamin B12 (Cobalamin)

Correct Answer: Vitamin B3 (Niacin)

Q21. Glycosaminoglycans are mainly composed of repeating units containing:

• Amino sugars and uronic acids
• Fatty acids and glycerol
• Amino acids and peptides
• Nucleotides and bases

Correct Answer: Amino sugars and uronic acids

Q22. Which amino acid is unique for introducing kinks in polypeptide chains and often found in turns?

• Proline
• Histidine
• Tryptophan
• Asparagine

Correct Answer: Proline

Q23. The Michaelis constant (Km) is inversely related to:

• Substrate affinity of the enzyme
• Turnover number (kcat)
• Enzyme molecular weight
• Product inhibition

Correct Answer: Substrate affinity of the enzyme

Q24. Which base pairing is correct for DNA double helix?

• Adenine pairs with cytosine
• Guanine pairs with thymine
• Adenine pairs with thymine
• Cytosine pairs with adenine

Correct Answer: Adenine pairs with thymine

Q25. What is the stereochemical configuration of most naturally occurring amino acids?

• D-configuration
• L-configuration
• R-configuration always
• S-configuration always

Correct Answer: L-configuration

Q26. Which lipid-derived molecule serves as a precursor for steroid hormones?

• Phosphatidylcholine
• Cholesterol
• Sphingomyelin
• Glycolipid

Correct Answer: Cholesterol

Q27. Which enzyme class catalyzes oxidation–reduction reactions?

• Hydrolases
• Transferases
• Oxidoreductases
• Isomerases

Correct Answer: Oxidoreductases

Q28. The bond formed between the 3′ hydroxyl of one nucleotide and the 5′ phosphate of another is called:

• Glycosidic bond
• Phosphodiester bond
• Peptide bond
• Sulfide bond

Correct Answer: Phosphodiester bond

Q29. Which amino acid side chain can be phosphorylated in signal transduction?

• Alanine
• Serine
• Leucine
• Valine

Correct Answer: Serine

Q30. Which carbohydrate storage form is predominant in animal liver and muscle?

• Cellulose
• Starch
• Glycogen
• Inulin

Correct Answer: Glycogen

Q31. In enzyme kinetics, kcat represents:

• The substrate concentration at half Vmax
• The catalytic turnover number per active site
• The inhibition constant
• The binding affinity

Correct Answer: The catalytic turnover number per active site

Q32. Which sugar linkage is indigestible by human enzymes and forms plant cell walls?

• α-1,4-glycosidic bond in starch
• β-1,4-glycosidic bond in cellulose
• α-1,6-glycosidic bond in glycogen
• β-1,6-glycosidic bond in agarose

Correct Answer: β-1,4-glycosidic bond in cellulose

Q33. Which amino acid contains an imidazole side chain important in enzyme active sites?

• Tyrosine
• Histidine
• Arginine
• Proline

Correct Answer: Histidine

Q34. Which process describes removal of an amine group from an amino acid, producing a keto acid?

• Transamination
• Decarboxylation
• Deamination
• Hydroxylation

Correct Answer: Deamination

Q35. Which statement about essential fatty acids is correct?

• Oleic acid is essential
• Linoleic acid must be obtained from diet
• Saturated fatty acids are essential
• All trans fatty acids are essential

Correct Answer: Linoleic acid must be obtained from diet

Q36. Ribozymes are:

• Protein enzymes that bind RNA
• RNA molecules with catalytic activity
• DNA enzymes involved in replication
• Carbohydrate-modifying enzymes

Correct Answer: RNA molecules with catalytic activity

Q37. Which amino acid acts as a major neurotransmitter precursor and is aromatic?

• Tyrosine
• Aspartate
• Glycine
• Threonine

Correct Answer: Tyrosine

Q38. In electrophoresis at neutral pH, proteins migrate according to their:

• Molecular weight only
• Net charge and size
• Isoelectric point exclusively
• Hydrophobicity only

Correct Answer: Net charge and size

Q39. Base excision repair primarily corrects which type of DNA damage?

• Double-strand breaks
• Small non-helix-distorting base lesions
• Large insertions
• Cross-links between strands

Correct Answer: Small non-helix-distorting base lesions

Q40. Which enzyme synthesizes RNA primers during DNA replication?

• DNA polymerase I
• Primase
• Ligase
• Helicase

Correct Answer: Primase

Q41. Glycation of proteins (non-enzymatic addition of sugars) is clinically significant in which condition?

• Alzheimer’s disease
• Diabetes mellitus
• Hypertension
• Osteoporosis

Correct Answer: Diabetes mellitus

Q42. Which cofactor is required for transketolase in the pentose phosphate pathway?

• FAD
• Thiamine pyrophosphate (TPP)
• Biotin
• Pyridoxal phosphate (PLP)

Correct Answer: Thiamine pyrophosphate (TPP)

Q43. What is the major product of complete beta-oxidation of a fatty acid?

• Glucose
• Acetyl-CoA
• Lactate
• Glycerol

Correct Answer: Acetyl-CoA

Q44. Which structural motif is characteristic of many DNA-binding proteins?

• Leucine zipper
• Alpha-helix only
• Hydrophobic tail
• Sugar-binding domain

Correct Answer: Leucine zipper

Q45. Which amino acid can be methylated on its side chain phenolic group?

• Tyrosine
• Serine
• Proline
• Arginine

Correct Answer: Tyrosine

Q46. Which technique separates proteins primarily by isoelectric point?

• SDS-PAGE
• Isoelectric focusing
• Size-exclusion chromatography
• Affinity chromatography

Correct Answer: Isoelectric focusing

Q47. Which vitamin is essential for collagen hydroxylation and deficiency leads to scurvy?

• Vitamin A
• Vitamin C
• Vitamin D
• Vitamin K

Correct Answer: Vitamin C

Q48. A nucleotide differs from a nucleoside by the presence of:

• A nitrogenous base
• A sugar
• One or more phosphate groups
• A peptide bond

Correct Answer: One or more phosphate groups

Q49. Which amino acid side chain is acidic and negatively charged at physiological pH?

• Lysine
• Aspartic acid
• Arginine
• Phenylalanine

Correct Answer: Aspartic acid

Q50. Which of the following best describes allosteric enzymes?

• They follow Michaelis–Menten kinetics strictly
• They are regulated by effectors binding at sites other than the active site
• They are always inactive
• They do not bind substrates

Correct Answer: They are regulated by effectors binding at sites other than the active site

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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