MCQ on Biochemical Basis of Diseases

🟢 EASY (1–20)

1. Which biomolecule is primarily affected in diabetes mellitus?
   a) Proteins
   b) Fats
   c) Carbohydrates ✅
   d) Nucleic acids
   Explanation: Diabetes involves impaired glucose metabolism, a carbohydrate.
2. Sickle cell anemia results from a defect in which biomolecule?
   a) Lipid
   b) Carbohydrate
   c) Hemoglobin (Protein) ✅
   d) DNA
   Explanation: A mutation in the β-globin gene affects hemoglobin.
3. Phenylketonuria is caused by the deficiency of:
   a) Insulin
   b) Tyrosinase
   c) Phenylalanine hydroxylase ✅
   d) Lactase
   Explanation: Lack of this enzyme leads to accumulation of phenylalanine.
4. Which vitamin deficiency causes scurvy?
   a) Vitamin D
   b) Vitamin A
   c) Vitamin C ✅
   d) Vitamin B12
   Explanation: Vitamin C is essential for collagen synthesis.
5. The biochemical cause of gout is:
   a) Low glucose
   b) High uric acid ✅
   c) High amino acids
   d) Vitamin B1 deficiency
   Explanation: Uric acid crystals accumulate in joints.
6. Which of the following diseases is linked to insulin deficiency?
   a) Hypertension
   b) Diabetes mellitus ✅
   c) Cancer
   d) Hemophilia
   Explanation: Insulin is crucial for glucose regulation.
7. Which of these is a genetic disorder?
   a) Rickets
   b) Scurvy
   c) Cystic fibrosis ✅
   d) Malaria
   Explanation: Cystic fibrosis is caused by mutations in the CFTR gene.
8. Hypercholesterolemia is associated with high levels of:
   a) Glucose
   b) Urea
   c) LDL cholesterol ✅
   d) Triglycerides
   Explanation: High LDL leads to atherosclerosis.
9. Albinism is caused due to deficiency of the enzyme:
   a) Lactase
   b) Tyrosinase ✅
   c) Amylase
   d) Pepsin
   Explanation: Tyrosinase is involved in melanin synthesis.
10. Atherosclerosis is the hardening of:
    a) Bones
    b) Arteries ✅
    c) Skin
    d) Muscles
    Explanation: Caused by lipid accumulation in arterial walls.
11. Kwashiorkor results from deficiency of:
    a) Carbohydrates
    b) Vitamins
    c) Proteins ✅
    d) Fats
    Explanation: A severe form of protein malnutrition.
12. Beriberi is due to deficiency of:
    a) Vitamin B12
    b) Vitamin C
    c) Thiamine (Vitamin B1) ✅
    d) Vitamin K
    Explanation: Affects nerve function and energy metabolism.
13. Which disease is linked to abnormal metabolism of copper?
    a) Hemophilia
    b) Wilson’s disease ✅
    c) Diabetes
    d) Pellagra
    Explanation: Excess copper accumulates in tissues.
14. Pellagra is caused by deficiency of:
    a) Niacin (Vitamin B3) ✅
    b) Riboflavin
    c) Thiamine
    d) Vitamin C
    Explanation: Niacin is essential for NAD/NADP production.
15. Which enzyme is deficient in lactose intolerance?
    a) Amylase
    b) Lipase
    c) Lactase ✅
    d) Protease
    Explanation: Lactase breaks down lactose in dairy products.
16. The primary cause of Tay-Sachs disease is:
    a) Lack of insulin
    b) Vitamin A deficiency
    c) Hexosaminidase A deficiency ✅
    d) Sickle cell mutation
    Explanation: Causes buildup of GM2 ganglioside in neurons.
17. Which disorder is related to serotonin imbalance?
    a) Diabetes
    b) Depression ✅
    c) Cancer
    d) Asthma
    Explanation: Serotonin affects mood regulation.
18. Which disease is linked with the accumulation of homogentisic acid?
    a) Phenylketonuria
    b) Alkaptonuria ✅
    c) Albinism
    d) Tay-Sachs
    Explanation: Homogentisic acid darkens urine and stains tissues.
19. Hemophilia affects the process of:
    a) Digestion
    b) Coagulation ✅
    c) Respiration
    d) Reproduction
    Explanation: It’s a clotting factor deficiency disorder.
20. Obesity is often biochemically linked to:
    a) Low protein
    b) High leptin
    c) Hormonal imbalance and lipid accumulation ✅
    d) Excess vitamins
    Explanation: Involves metabolic dysregulation of fats and hormones.

🟡 MODERATE (21–40)

21. Which genetic disease results from defective chloride channels?
    a) Hemophilia
    b) Cystic fibrosis ✅
    c) Phenylketonuria
    d) Albinism
    Explanation: CFTR mutation disrupts salt balance.
22. Huntington’s disease is caused by a mutation in which gene?
    a) CFTR
    b) HTT ✅
    c) HBB
    d) PAH
    Explanation: HTT gene codes for huntingtin protein.
23. What is the metabolic defect in Lesch-Nyhan syndrome?
    a) Glucose metabolism
    b) Purine metabolism ✅
    c) Lipid metabolism
    d) Protein breakdown
    Explanation: Caused by HGPRT enzyme deficiency.
24. Which disease involves abnormal accumulation of sphingolipids?
    a) Gout
    b) Gaucher disease ✅
    c) Pellagra
    d) Diabetes
    Explanation: Caused by glucocerebrosidase deficiency.
25. Biochemical basis of scurvy includes:
    a) Defective hemoglobin
    b) Impaired collagen synthesis ✅
    c) Lipid accumulation
    d) High glucose
    Explanation: Vitamin C is essential for collagen cross-linking.
26. Which organ is primarily affected in urea cycle disorders?
    a) Heart
    b) Liver ✅
    c) Kidney
    d) Brain
    Explanation: Liver carries out the urea cycle.
27. Which of the following is a lysosomal storage disorder?
    a) Sickle cell anemia
    b) Tay-Sachs disease ✅
    c) Rickets
    d) Albinism
    Explanation: Lysosomal enzyme deficiencies lead to accumulation of substrates.
28. Which disease results from mutations affecting dopamine production?
    a) Diabetes
    b) Parkinson’s disease ✅
    c) Wilson’s disease
    d) Cystic fibrosis
    Explanation: Loss of dopamine-producing neurons.
29. High levels of LDL in blood increase the risk of:
    a) Diabetes
    b) Cardiovascular disease ✅
    c) Tuberculosis
    d) Anemia
    Explanation: LDL deposits cholesterol in arteries.
30. Phenylalanine is converted into which amino acid in normal metabolism?
    a) Glycine
    b) Tyrosine ✅
    c) Serine
    d) Valine
    Explanation: This conversion is impaired in PKU.
31. Marasmus is characterized by deficiency of:
    a) Proteins only
    b) Carbohydrates only
    c) All nutrients ✅
    d) Fats only
    Explanation: Severe energy and nutrient deficiency.
32. In cancer, which process is biochemically upregulated?
    a) Apoptosis
    b) Glycolysis (Warburg effect) ✅
    c) Fat oxidation
    d) DNA repair
    Explanation: Tumor cells rely heavily on anaerobic glycolysis.
33. Beriberi affects which system?
    a) Nervous system ✅
    b) Digestive system
    c) Respiratory system
    d) Reproductive system
    Explanation: Thiamine deficiency impairs nerve conduction.
34. Which hormone regulates calcium homeostasis?
    a) Insulin
    b) Parathyroid hormone ✅
    c) Adrenaline
    d) TSH
    Explanation: It increases blood calcium levels.
35. The defective metabolism of galactose leads to:
    a) Phenylketonuria
    b) Galactosemia ✅
    c) Diabetes
    d) Gaucher disease
    Explanation: Due to deficiency of galactose-1-phosphate uridyltransferase.
36. Which molecule builds up in Niemann-Pick disease?
    a) Urea
    b) Sphingomyelin ✅
    c) Lactose
    d) Glycogen
    Explanation: Caused by sphingomyelinase deficiency.
37. Increased ketone bodies in blood indicate:
    a) Lipogenesis
    b) Ketosis ✅
    c) Glycolysis
    d) Hyperthyroidism
    Explanation: Occurs during fat breakdown, e.g., in starvation or diabetes.
38. Hypothyroidism is biochemically marked by low levels of:
    a) T3 and T4 ✅
    b) Insulin
    c) Adrenaline
    d) Cortisol
    Explanation: Thyroid hormone levels fall.
39. Which trace element deficiency causes goiter?
    a) Zinc
    b) Copper
    c) Iron
    d) Iodine ✅
    Explanation: Iodine is necessary for thyroid hormone synthesis.
40. Enzyme deficiency in galactosemia leads to accumulation of:
    a) Glucose
    b) Galactose-1-phosphate ✅
    c) Glycogen
    d) Pyruvate
    Explanation: Accumulates in liver, kidney, and brain.

🔴 HARD (41–50)

41. Which gene is mutated in familial hypercholesterolemia?
    a) CFTR
    b) LDLR ✅
    c) HBB
    d) F8
    Explanation: Mutations impair LDL receptor function.
42. In Alzheimer’s, which protein accumulates abnormally?
    a) Hemoglobin
    b) Insulin
    c) Amyloid-beta ✅
    d) Elastin
    Explanation: Forms plaques in brain tissue.
43. The Warburg effect refers to:
    a) Protein breakdown in starvation
    b) Increased glycolysis in cancer ✅
    c) Impaired fat metabolism
    d) Mitochondrial dysfunction in diabetes
    Explanation: Cancer cells rely on glycolysis even with oxygen.
44. Which metabolic pathway is defective in McArdle’s disease?
    a) Glycolysis
    b) Glycogenolysis ✅
    c) Gluconeogenesis
    d) Fatty acid oxidation
    Explanation: Deficiency in muscle glycogen phosphorylase.
45. In mitochondrial diseases, the major biochemical issue is:
    a) Protein synthesis
    b) Electron transport chain defects ✅
    c) Lipid storage
    d) Amino acid metabolism
    Explanation: Mitochondria fail to produce ATP efficiently.
46. Maple syrup urine disease is due to defective metabolism of:
    a) Phenylalanine
    b) Branched-chain amino acids ✅
    c) Glycine
    d) Tyrosine
    Explanation: Buildup of leucine, isoleucine, valine.
47. A mutation in the p53 gene is most closely associated with:
    a) Heart disease
    b) Cancer ✅
    c) Gout
    d) Hemophilia
    Explanation: p53 is a tumor suppressor gene.
48. Zellweger syndrome affects which organelle?
    a) Mitochondria
    b) Lysosome
    c) Peroxisome ✅
    d) Golgi apparatus
    Explanation: Involves defective peroxisome biogenesis.
49. Which vitamin acts as a cofactor in amino acid metabolism?
    a) Vitamin C
    b) Pyridoxine (Vitamin B6) ✅
    c) Vitamin K
    d) Folic acid
    Explanation: Required for transamination and decarboxylation.
50. Deficiency of glucose-6-phosphate dehydrogenase leads to:
    a) Anemia under oxidative stress ✅
    b) Jaundice
    c) Diabetes
    d) Marasmus
    Explanation: Red cells become vulnerable to oxidative damage.