The enzyme that catalyzes the synthesis of cAMP from ATP is: MCQ with Answer and Explanation

The enzyme that catalyzes the synthesis of cAMP from ATP is:
A. Adenylyl cyclase
B. Phospholipase C
C. Guanylyl cyclase
D. Protein kinase A
Answer: Option A
Solution (By JKExamLibrary)
Adenylyl cyclase converts ATP to cyclic AMP, a second messenger. Guanylyl cyclase makes cGMP, phospholipase C produces IP₃/DAG, PKA is activated by cAMP.

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Practice More Biology Questions

Question #1
Consider statements about human diseases: 1. Dengue is caused by a protozoan. 2. Filariasis is caused by a nematode worm. 3. Pneumonia affects the respiratory system. Which are correct?
A. 1 and 2 only
B. 1 and 3 only
C. 1, 2 and 3
D. 2 and 3 only

Correct Answer: Option D


Explanation:
Dengue is a viral disease caused by the Dengue virus, not a protozoan (malaria is caused by a protozoan). Filariasis (elephantiasis) is caused by parasitic nematode worms like Wuchereria bancrofti, which block lymphatic vessels. Pneumonia is an infection that inflames the air sacs in one or both lungs, affecting the respiratory system. Thus, statements 2 and 3 are correct.

This question belongs to: Science Biology
Question #2
The antibiotic that inhibits bacterial cell wall synthesis is:
A. Streptomycin
B. Penicillin
C. Tetracycline
D. Chloramphenicol

Correct Answer: Option B


Explanation:
Penicillin and other beta-lactam antibiotics (cephalosporins, carbapenems) inhibit the transpeptidase enzyme involved in cross-linking peptidoglycan, weakening the cell wall and causing bacterial lysis. Tetracycline and streptomycin inhibit protein synthesis by acting on ribosomes. Chloramphenicol also inhibits protein synthesis. Penicillin is most effective against actively dividing gram-positive bacteria.

This question belongs to: Science Biology
Question #3
The hormone that stimulates the thyroid gland to release T₃ and T₄ is:
A. LH
B. ACTH
C. TSH
D. FSH

Correct Answer: Option C


Explanation:
Thyroid-stimulating hormone (TSH) from the anterior pituitary binds to receptors on thyroid follicular cells, stimulating synthesis and release of thyroid hormones (T₃ and T₄). ACTH targets adrenal cortex.

This question belongs to: Science Biology