The opening and closing of stomata is regulated by the: MCQ with Answer and Explanation

Question
The opening and closing of stomata is regulated by the:
A. Phloem cells
B. Guard cells
C. Xylem vessels
D. Epidermal hairs
Answer: Option B
Solution (By JKSSB Mock Tests)
Stomata are surrounded by two kidney-shaped guard cells in dicots (dumb-bell-shaped in grasses) that control pore opening/closing via turgor pressure changes. When guard cells absorb water and become turgid, the stomatal pore opens; when flaccid, it closes. This process is influenced by light, CO₂ concentration, and abscisic acid (ABA). Stomata are critical for gas exchange and transpiration.
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Question #1
The deficiency of vitamin A causes:
A. Pellagra
B. Night blindness
C. Scurvy
D. Beri-beri
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Correct Answer: Option B

Explanation:
Vitamin A is essential for the synthesis of rhodopsin. Deficiency leads to impaired dark adaptation (night blindness) and eventually xerophthalmia. Beri-beri is B₁ deficiency, pellagra B₃, scurvy vitamin C.
This question belongs to: Science Biology
Question #2
The process of synthesizing mRNA from a DNA template is called:
A. Translation
B. Transcription
C. Replication
D. Transduction
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Correct Answer: Option B

Explanation:
Transcription is the first step of gene expression, where a specific segment of DNA is copied into RNA (specifically mRNA) by the enzyme RNA polymerase. This occurs in the nucleus of eukaryotes. The mRNA then carries the genetic code from the DNA to the ribosomes in the cytoplasm for translation (protein synthesis).
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Question #3
The enzyme that catalyzes the conversion of pyruvate to acetyl-CoA is:
A. Pyruvate kinase
B. Pyruvate dehydrogenase
C. Lactate dehydrogenase
D. Citrate synthase
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Correct Answer: Option B

Explanation:
Pyruvate dehydrogenase complex (PDC) oxidatively decarboxylates pyruvate, producing acetyl-CoA, NADH, and CO₂ in the mitochondrial matrix, linking glycolysis to the Krebs cycle. Pyruvate kinase is in glycolysis, lactate dehydrogenase converts pyruvate to lactate, citrate synthase starts the Krebs cycle.
This question belongs to: Science Biology
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