Q41. What is the main function of centrosomes in cell division?
a) DNA replication
b) Ribosome production
c) Spindle formation
d) Protein synthesis
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Correct Answer: c) Spindle formation
Explanation: Centrosomes play a crucial role in cell division, particularly in the formation of the spindle fibers. These fibers are essential for the separation of chromosomes during mitosis and meiosis.
Q42. Endoplasmic reticulum that appears rough under the microscope has this appearance due to the presence of
a) Lipids
b) Ribosomes
c) Mitochondria
d) Golgi apparatus
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Correct Answer: b) Ribosomes
Explanation: The rough appearance of the endoplasmic reticulum under a microscope is due to the presence of ribosomes on its surface. These ribosomes are involved in protein synthesis, giving the ER a rough texture.
Q43. What is the primary role of messenger RNA (mRNA) in cells?
a) Carrying amino acids to the ribosome
b) Carrying genetic information from DNA to the ribosome
c) Forming the structure of ribosomes
d) Assisting in lipid synthesis
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Correct Answer: b) Carrying genetic information from DNA to the ribosome
Explanation: The primary role of messenger RNA (mRNA) in cells is to carry genetic information from DNA in the nucleus to the ribosome, where protein synthesis occurs. It acts as a template for the sequence of amino acids in a protein.
Q44. Which cellular process is responsible for generating most of the ATP in eukaryotic cells?
a) Glycolysis
b) Krebs cycle
c) Electron transport chain
d) Fermentation
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Correct Answer: c) Electron transport chain
Explanation: The electron transport chain is responsible for generating the majority of the ATP in eukaryotic cells. This process takes place in the inner membrane of mitochondria and produces ATP through oxidative phosphorylation.
Q45. The primary structure of a protein is determined by
a) The sequence of amino acids
b) The folding into alpha helices or beta sheets
c) The overall three-dimensional shape
d) The presence of disulfide bridges
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Correct Answer: a) The sequence of amino acids
Explanation: The primary structure of a protein is determined by its sequence of amino acids. This sequence dictates how the protein will fold and function, influencing its higher-level structures.
Q46. In a eukaryotic cell, where does transcription take place?
a) In the cytoplasm
b) On the ribosome
c) In the mitochondria
d) In the nucleus
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Correct Answer: d) In the nucleus
Explanation: In eukaryotic cells, transcription, the process of copying DNA into RNA, occurs in the nucleus. This is where the cell’s DNA is housed and where mRNA is synthesized before it travels to the cytoplasm for translation.
Q47. What is the role of peroxisomes in cells?
a) Protein synthesis
b) Breakdown of fatty acids and detoxification of harmful substances
c) DNA replication
d) Storage of nutrients
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Correct Answer: b) Breakdown of fatty acids and detoxification of harmful substances
Explanation: Peroxisomes are organelles in cells that are involved in the breakdown of long-chain fatty acids and the detoxification of harmful substances, including alcohol and other toxins.
Q48. Which cellular structure is primarily responsible for the synthesis of oils, phospholipids, and steroids?
a) Lysosome
b) Ribosome
c) Smooth Endoplasmic Reticulum
d) Mitochondria
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Correct Answer: c) Smooth Endoplasmic Reticulum
Explanation: The smooth endoplasmic reticulum (SER) is primarily responsible for the synthesis of lipids, including oils, phospholipids, and steroids. The SER also plays a role in carbohydrate metabolism and detoxification of drugs and poisons.
Q49. What is the significance of meiosis in sexual reproduction?
a) It produces genetically identical cells.
b) It increases the chromosome number in gametes.
c) It reduces the chromosome number by half in gametes.
d) It replicates DNA for somatic cells.
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Correct Answer: c) It reduces the chromosome number by half in gametes.
Explanation: Meiosis is significant in sexual reproduction because it reduces the chromosome number by half in gametes (sperm and eggs), ensuring that the offspring has a complete set of chromosomes when two gametes fuse during fertilization.
Q50. The sodium-potassium pump in the cell membrane functions to
a) Synthesize ATP
b) Transport sodium and potassium against their concentration gradients
c) Facilitate passive diffusion of ions
d) Break down glucose molecules
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Correct Answer: b) Transport sodium and potassium against their concentration gradients
Explanation: The sodium-potassium pump is an active transport mechanism in the cell membrane. It uses ATP to transport sodium and potassium ions against their concentration gradients, maintaining essential cellular functions and electrochemical gradients.