Which of the following hormones is responsible for the closure of stomata during water stress?
A. Auxin
B. Cytokinin
C. Abscisic acid (ABA)
D. Gibberellin
Answer: Option C
Solution (By JKExamLibrary)
Abscisic acid (ABA) is a stress hormone that induces stomatal closure by causing efflux of K⁺ ions from guard cells, leading to loss of turgor, thereby reducing water loss during drought. Auxin and cytokinin promote growth, gibberellin stimulates stem elongation and seed germination. ABA also promotes seed dormancy and leaf senescence.
Explanation:
Hexokinase phosphorylates glucose to glucose-6-phosphate using ATP, the first step of glycolysis. Phosphofructokinase is the third step, pyruvate kinase the last, glucose-6-phosphatase reverses the reaction in gluconeogenesis.
Explanation:
DNA is typically a double-stranded helical molecule carrying genetic information. Genes are specific sequences of DNA located linearly on chromosomes. RNA is generally single-stranded and contains the nitrogenous base uracil instead of thymine, which is found in DNA. Therefore, statements 1 and 3 are correct, while statement 2 is incorrect.
Explanation:
Glucagon-like Peptide-1 (GLP-1) is a powerful incretin hormone secreted by the L cells of the distal small intestine (ileum) and colon in response to food ingestion. Its primary functions are highly beneficial for glucose homeostasis: it stimulates insulin secretion from the pancreas in a glucose-dependent manner (only when blood glucose is high), inhibits glucagon secretion, slows down gastric emptying (allowing more time for nutrient absorption), and acts on the brain to promote satiety and reduce food intake. GLP-1 analogs (like exenatide) are used as drugs to treat type 2 diabetes.
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