1. Which of the following statements regarding the fluid mosaic model of plasma membrane is correct?

  • A. Proteins form a continuous layer on both sides of the lipid bilayer.
  • B. Phospholipids are arranged as a bilayer with proteins embedded within it.
  • C. Cellulose forms the basic framework of the membrane.
  • D. Membrane proteins remain completely immobile.

Answer: B. Phospholipids are arranged as a bilayer with proteins embedded within it.

Explanation: According to Singer and Nicolson's fluid mosaic model, proteins are embedded in a fluid phospholipid bilayer.

2. Which organelle is known as the "suicidal bag" of the cell due to the presence of hydrolytic enzymes?

  • A. Golgi apparatus
  • B. Mitochondrion
  • C. Lysosome
  • D. Peroxisome

Answer: C. Lysosome

Explanation: Lysosomes contain hydrolytic enzymes capable of digesting worn-out organelles and cellular debris.

3. During which phase of the cell cycle does DNA replication occur?

  • A. G₁ phase
  • B. S phase
  • C. G₂ phase
  • D. M phase

Answer: B. S phase

Explanation: DNA synthesis takes place during the S (Synthesis) phase of interphase before cell division.

4. Which pigment is directly involved in the reaction center of Photosystem II?

  • A. P680
  • B. P700
  • C. Chlorophyll b
  • D. Xanthophyll

Answer: A. P680

Explanation: Photosystem II contains the reaction center chlorophyll molecule P680, which initiates photolysis of water.

5. Which of the following hormones stimulates milk ejection from mammary glands?

  • A. Prolactin
  • B. Oxytocin
  • C. Estrogen
  • D. Progesterone

Answer: B. Oxytocin

Explanation: Oxytocin causes contraction of myoepithelial cells surrounding alveoli, resulting in milk ejection.

6. Which blood group is known as the universal donor?

  • A. A
  • B. B
  • C. AB
  • D. O

Answer: D. O

Explanation: Blood group O (especially O negative) lacks A and B antigens and can donate red blood cells to all blood groups.

7. Which scientist proposed the theory of natural selection?

  • A. Gregor Mendel
  • B. Charles Darwin
  • C. Hugo de Vries
  • D. Thomas Hunt Morgan

Answer: B. Charles Darwin

Explanation: Charles Darwin proposed natural selection as the primary mechanism of evolution in his book "On the Origin of Species."

8. The bacterium Agrobacterium tumefaciens transfers which plasmid into plant cells?

  • A. F plasmid
  • B. Ti plasmid
  • C. R plasmid
  • D. Col plasmid

Answer: B. Ti plasmid

Explanation: Agrobacterium tumefaciens naturally transfers T-DNA from its Ti plasmid into plant cells during genetic transformation.

9. Which of the following is an example of ex situ conservation?

  • A. National Park
  • B. Wildlife Sanctuary
  • C. Biosphere Reserve
  • D. Botanical Garden

Answer: D. Botanical Garden

Explanation: Botanical gardens conserve plant species outside their natural habitats and are examples of ex situ conservation.

10. Which enzyme is used to join DNA fragments during recombinant DNA technology?

  • A. DNA polymerase
  • B. DNA ligase
  • C. Restriction endonuclease
  • D. Reverse transcriptase

Answer: B. DNA ligase

Explanation: DNA ligase seals the phosphodiester backbone, joining DNA fragments to form recombinant DNA molecules.