1. Which enzyme is responsible for joining Okazaki fragments during DNA replication?

  • A. DNA polymerase III
  • B. DNA helicase
  • C. DNA ligase
  • D. Primase

Answer: C. DNA ligase

Explanation: DNA ligase seals the nicks between adjacent Okazaki fragments by forming phosphodiester bonds.

2. Which of the following cells functions as the pacemaker of the human heart?

  • A. Atrioventricular (AV) node
  • B. Purkinje fibres
  • C. Sinoatrial (SA) node
  • D. Bundle of His

Answer: C. Sinoatrial (SA) node

Explanation: The SA node generates rhythmic electrical impulses and is therefore known as the natural pacemaker of the heart.

3. Which hormone secreted by the posterior pituitary promotes water reabsorption in the kidneys?

  • A. Oxytocin
  • B. Aldosterone
  • C. Antidiuretic hormone (ADH)
  • D. Cortisol

Answer: C. Antidiuretic hormone (ADH)

Explanation: ADH (vasopressin) increases water reabsorption in the collecting ducts, thereby reducing urine output.

4. Which scientist proposed the operon model of gene regulation?

  • A. Watson and Crick
  • B. Meselson and Stahl
  • C. Jacob and Monod
  • D. Griffith and Avery

Answer: C. Jacob and Monod

Explanation: François Jacob and Jacques Monod proposed the lac operon model to explain gene regulation in prokaryotes.

5. Which blood cells are known as the "soldiers of the body" because they engulf invading microorganisms?

  • A. Erythrocytes
  • B. Platelets
  • C. Neutrophils
  • D. Basophils

Answer: C. Neutrophils

Explanation: Neutrophils are phagocytic white blood cells that form the first line of defence against bacterial infections.

6. Which of the following is a homologous organ to the forelimb of a whale?

  • A. Wing of butterfly
  • B. Wing of bat
  • C. Fin of fish
  • D. Tentacle of octopus

Answer: B. Wing of bat

Explanation: The whale flipper and bat wing have the same basic skeletal plan but perform different functions, making them homologous organs.

7. Which enzyme catalyses the first step of glycolysis by converting glucose into glucose-6-phosphate?

  • A. Phosphofructokinase
  • B. Pyruvate kinase
  • C. Hexokinase
  • D. Aldolase

Answer: C. Hexokinase

Explanation: Hexokinase catalyses the phosphorylation of glucose to glucose-6-phosphate, the first reaction of glycolysis.

8. Which ecosystem has the highest net primary productivity per unit area?

  • A. Desert
  • B. Tropical rainforest
  • C. Tundra
  • D. Grassland

Answer: B. Tropical rainforest

Explanation: Tropical rainforests have abundant rainfall, high temperatures, and year-round photosynthesis, resulting in the highest primary productivity.

9. Which immunoglobulin is the most abundant antibody in human blood plasma?

  • A. IgA
  • B. IgD
  • C. IgE
  • D. IgG

Answer: D. IgG

Explanation: IgG is the most abundant immunoglobulin in blood and provides long-term protection against pathogens.

10. Which scientist is credited with discovering penicillin?

  • A. Robert Koch
  • B. Louis Pasteur
  • C. Alexander Fleming
  • D. Edward Jenner

Answer: C. Alexander Fleming

Explanation: Alexander Fleming discovered penicillin in 1928 from the fungus Penicillium notatum, leading to the development of the first antibiotic.