All Free Biology MCQs with Answers
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19844 questions · page 637 of 1985
6361. The telomeres of eukaryotic chromosomes consist of short sequences of:
- A. Thymine rich repeats
- B. Cytosine rich repeats
- C. Adenine rich repeats
- D. Guanine rich repeats
Explanation: Telomeres are characterized by guanine-rich repeats, which play a key role in protecting chromosome ends and maintaining genome stability. These sequences form structures like G-quadruplexes, crucial for telomere function .
Correct answer: Guanine rich repeats6362. Which one is not cytoplasmic body?
- A. Mitochondria
- B. Vacuole
- C. Cell membrane
- D. Ribosome
Explanation: In living cells, the cytoplasm contains several cell organelles such as endoplasmic reticulum, mitochondria, Golgi complex, nucleus, plastids, ribosomes, lysosomes, and centriole. The cell membrane is the outermost covering of a cell.
Correct answer: Cell membrane6363. What was the unit membrane model?
- A. Plasma membrane has lipid bilayer sandwiched between two outer layer of protein.
- B. Proteins are embedded in the lipid bilayer
- C. Plasma membrane has charged pores for transport of materials which cannot penetrate through the lipid bilayer
- D. All of the above
Explanation: It was proposed earlier that a cell membrane is composed of a lipid bilayer sandwiched between inner and outer layers of protein. This, basic structure is called the unit membrane and is present in all the cellular organelles.
Correct answer: Plasma membrane has lipid bilayer sandwiched between two outer layer of protein.6364. Carbon dioxide passes through the plasma membrane of cells by:
- A. Active transport
- B. Phagocytosis
- C. Facilitated diffusion
- D. Simple diffusion
Explanation: Simple diffusion allows molecules like carbon dioxide (CO2) to passively cross the cell membrane from an area of high concentration to an area of low concentration without energy.
Correct answer: Simple diffusion6365. What percentage of protein is found in the cell membrane?
- A. 20-40
- B. 40-50
- C. 60-80
- D. 90
Explanation: Proteins make up 60-80% of the cell membrane, providing structural support and facilitating communication and transport.
Correct answer: 60-806366. What part of the cell serves as an intracellular highway?
- A. ER
- B. Golgi apparatus
- C. Cell membrane
- D. Mitochondria
Explanation: ER forms an intracellular connecting system and transports materials of the cell from one part of the cell to another part of the cell.
Correct answer: ER6367. Damage to which of the following immediately kills the cell whether it is prokaryotic or eukaryotic?
- A. Nucleus
- B. Mitochondria
- C. Cell membrane
- D. All of these
Explanation: Disruption or damage to the cell membrane can lead to the loss of essential cellular components, disrupt homeostasis, and ultimately cause the cell to lyse (burst), leading to cell death.
Correct answer: Cell membrane6368. Which one of the following is not a double membranous structure?
- A. Vacuole
- B. Mitochondria
- C. Chloroplast
- D. Nucleus
Explanation: Vacuoles are single membrane-bounded organelles. The membrane that encases the vacuole is known as the tonoplast, distinguishing it from double-membraned structures.
Correct answer: Vacuole6369. The largest organelle in a mature living plant cell is:
- A. Chloroplast
- B. Nucleus
- C. Central vacuole
- D. Mitochondria
Explanation: The central vacuole is the largest organelle in a mature plant cell. It stores water, nutrients, and waste, and is crucial for maintaining turgor pressure and supporting cell structure.
Correct answer: Central vacuole6370. The Colour of the petals is due to:
- A. Chloroplast
- B. Plastid
- C. Chromoplast
- D. Leucoplast
Explanation: Chromoplasts are specialized plastids that contain pigments other than green, such as carotenoids, which provide the red, orange, and yellow colors to petals and fruits.
Correct answer: Chromoplast