Consider statements about mitochondria: 1. They have a single membrane. 2. They contain their own circular DNA. 3. They are the site of aerobic respiration. Which are correct? MCQ with Answer and Explanation
Consider statements about mitochondria: 1. They have a single membrane. 2. They contain their own circular DNA. 3. They are the site of aerobic respiration. Which are correct?
A. 1 and 3 only
B. 1, 2 and 3
C. 2 and 3 only
D. 1 and 2 only
Answer: Option C
Solution (By JKExamLibrary)
Mitochondria are double-membrane-bound organelles, possessing an outer smooth membrane and a highly folded inner membrane forming cristae. They contain their own circular DNA and 70S ribosomes, making them semi-autonomous. They are the primary site of aerobic respiration and ATP production. Statement 1 is incorrect as they have two membranes.
Explanation:
Prokaryotic DNA is typically circular, double-stranded, and found in a nucleoid region without a nuclear membrane. It is not associated with histones (though some Archaea have histone-like proteins). Plasmids are extra-chromosomal DNA. Eukaryotic DNA is linear and complexed with histones. This difference is fundamental in cell classification.
Assertion (A): Red blood cells lack a nucleus in mammals.
Reason (R): The absence of a nucleus allows more space for hemoglobin, increasing oxygen-carrying capacity.
A.Both A and R are true, and R is the correct explanation of A.
B.A is false, but R is true.
C.Both A and R are true, but R is not the correct explanation.
Explanation:
Mature mammalian RBCs are anucleate, having lost their nucleus during maturation. This provides more space for hemoglobin, enhancing oxygen transport. The reason correctly explains the assertion. Nucleated RBCs are found in other vertebrates.
Explanation:
Abscission is the controlled shedding of leaves, flowers, or fruits, facilitated by the hormone ethylene and enzymes that degrade cell walls at the abscission zone. Senescence is the aging process leading to cell death. Transpiration is water loss, germination is seed sprouting.
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