Biomolecules - 50 MCQs with Answers

1. Which of the following is a polysaccharide?

A) Glucose

B) Fructose

C) Starch ✅

D) Galactose

2. Which bond links monosaccharides in a polysaccharide?

A) Peptide bond

B) Glycosidic bond ✅

C) Hydrogen bond

D) Disulfide bond

3. Which is the storage polysaccharide in animals?

A) Cellulose

B) Glycogen ✅

C) Amylose

D) Inulin

4. The building blocks of proteins are:

A) Amino acids ✅

B) Fatty acids

C) Nucleotides

D) Monosaccharides

5. Which biomolecule carries genetic information?

A) Proteins

B) Carbohydrates

C) Nucleic acids ✅

D) Lipids

6. Which is the most abundant protein in the human body?

A) Collagen ✅

B) Keratin

C) Myosin

D) Hemoglobin

7. Which of the following is a lipid?

A) Cellulose

B) Triglyceride ✅

C) Glycogen

D) Amylopectin

8. Enzymes are primarily made of:

A) Proteins ✅

B) Lipids

C) Carbohydrates

D) Nucleic acids

9. Which vitamin is essential for blood clotting?

A) Vitamin A

B) Vitamin K ✅

C) Vitamin C

D) Vitamin D

10. The alpha-helix and beta-pleated sheet are types of _____ structure of proteins.

A) Primary

B) Secondary ✅

C) Tertiary

D) Quaternary

11. Which nucleotide base is present in RNA but not in DNA?

A) Thymine

B) Uracil ✅

C) Adenine

D) Guanine

12. A peptide bond forms between:

A) Two amino groups

B) Carboxyl group of one amino acid and amino group of another ✅

C) Two carboxyl groups

D) Amino acid and carbohydrate

13. Which polysaccharide provides structural support in plant cell walls?

A) Glycogen

B) Cellulose ✅

C) Starch

D) Chitin

14. Lipids are insoluble in _____ and soluble in organic solvents.

A) Water ✅

B) Ethanol

C) Acetone

D) Chloroform

15. Which of the following is NOT a function of proteins?

A) Catalysis

B) Structural support

C) Long-term energy storage ✅

D) Transport

16. The basic unit of a nucleic acid is called:

A) Nucleotide ✅

B) Amino acid

C) Monosaccharide

D) Fatty acid

17. Which of the following increases the rate of a chemical reaction without being consumed?

A) Catalyst (Enzyme) ✅

B) Substrate

C) Product

D) Inhibitor

18. Which amino acid has a sulfur atom in its side chain?

A) Lysine

B) Cysteine ✅

C) Alanine

D) Valine

19. Which sugar is a component of DNA?

A) Ribose

B) Deoxyribose ✅

C) Glucose

D) Fructose

20. Which lipid is a major component of biological membranes?

A) Phospholipids ✅

B) Triacylglycerols

C) Steroids

D) Waxes

21. Denaturation of proteins affects which level of protein structure most directly?

A) Primary

B) Secondary & tertiary ✅

C) Quaternary only

D) None

22. Which molecule is commonly called "blood sugar"?

A) Glucose ✅

B) Sucrose

C) Fructose

D) Maltose

23. Which vitamin is important for calcium absorption and bone health?

A) Vitamin C

B) Vitamin D ✅

C) Vitamin K

D) Vitamin B12

24. Which of the following is an essential fatty acid?

A) Palmitic acid

B) Linoleic acid (omega-6) ✅

C) Stearic acid

D) Oleic acid (non-essential)

25. Which technique is commonly used to separate proteins based on their size?

A) Chromatography

B) SDS-PAGE ✅

C) PCR

D) Spectrophotometry

26. Which of the following is a non-reducing sugar?

A) Sucrose ✅

B) Glucose

C) Maltose

D) Lactose

27. Which functional group is present in amino acids?

A) Hydroxyl only

B) Amino and carboxyl ✅

C) Phosphate

D) Ester

28. The basic unit of carbohydrates is:

A) Monosaccharide ✅

B) Amino acid

C) Nucleotide

D) Fatty acid

29. Which enzyme breaks down proteins in the stomach?

A) Amylase

B) Pepsin ✅

C) Lipase

D) Trypsin

30. Which of the following statements about enzymes is FALSE?

A) Enzymes lower activation energy

B) Enzymes alter the equilibrium constant of reactions ✅

C) Enzymes are specific for substrates

D) Enzymes can be regulated by inhibitors

31. Which lipid-derived molecule acts as a hormone regulating metabolism?

A) Triacylglycerol

B) Steroid (e.g., testosterone) ✅

C) Phospholipid

D) Wax

32. Which base pairs are held together by three hydrogen bonds?

A) A—T (or A—U)

B) G—C ✅

C) A—G

D) C—T

33. Scurvy is caused by deficiency of which vitamin?

A) Vitamin C ✅

B) Vitamin A

C) Vitamin D

D) Vitamin B12

34. Which of the following is an example of a conjugated protein?

A) Insulin (pure protein)

B) Hemoglobin (protein + heme) ✅

C) Collagen

D) Keratin

35. Which molecule functions as the universal energy currency of the cell?

A) ATP ✅

B) GTP

C) NADH

D) FADH2

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

A) Lysine ✅

B) Aspartate

C) Glutamate

D) Serine

37. Which sugar is a disaccharide made of glucose + fructose?

A) Sucrose ✅

B) Lactose

C) Maltose

D) Cellobiose

38. Competitive inhibitors bind to the _____ of an enzyme.

A) Active site ✅

B) Allosteric site

C) Substrate

D) Product

39. Which process forms a disulfide bond in proteins?

A) Phosphorylation

B) Oxidation of two cysteine residues (forming cystine) ✅

C) Glycosylation

D) Hydrolysis

40. Which of the following is TRUE about essential amino acids?

A) They can be synthesized by the body

B) They must be obtained from the diet ✅

C) They are not required for protein synthesis

D) They are only found in plants

41. Which technique is used to amplify a specific DNA fragment?

A) PCR (Polymerase Chain Reaction) ✅

B) Western blot

C) ELISA

D) Chromatography

42. Which of the following is a storage form of lipids in animals?

A) Triacylglycerol (triglyceride) ✅

B) Phospholipid

C) Steroid

D) Glycolipid

43. Which sugar shows a positive Benedict's test?

A) Reducing sugars like glucose and maltose ✅

B) Sucrose (non-reducing)

C) Cellulose

D) Starch

44. Which vitamin deficiency leads to night blindness?

A) Vitamin A ✅

B) Vitamin C

C) Vitamin D

D) Vitamin K

45. Which nucleotide is found in ATP?

A) Adenosine triphosphate (adenine + ribose + 3 phosphates) ✅

B) Cytidine diphosphate

C) Guanosine monophosphate

D) Thymidine triphosphate

46. Which enzyme converts RNA into DNA in retroviruses?

A) Reverse transcriptase ✅

B) DNA polymerase

C) RNA polymerase

D) Ligase

47. Which compound contains a glycerol backbone?

A) Triacylglycerol (triglyceride) ✅

B) Steroid

C) Fatty acid alone

D) Amino acid

48. Which of the following is a nucleotide base found in DNA?

A) Thymine ✅

B) Uracil

C) Ribose

D) Phosphate

49. Which vitamin acts as an antioxidant and helps in collagen synthesis?

A) Vitamin C ✅

B) Vitamin E

C) Vitamin K

D) Vitamin B6

50. Glycosylation is a post-translational modification involving the addition of _____ groups to proteins.

A) Carbohydrate (glycan) groups ✅

B) Phosphate groups

C) Lipid groups

D) Sulfate groups