The 'Hormone Insulin' is a peptide hormone composed of two polypeptide chains, A and B, linked by: MCQ with Answer and Explanation

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The 'Hormone Insulin' is a peptide hormone composed of two polypeptide chains, A and B, linked by:

A. Peptide bonds

B. Ionic bonds

C. Hydrogen bonds

D. Disulfide bridges

Answer: Option D

Solution (By JKExamLibrary)

Insulin is a peptide hormone produced by the beta cells of the Islets of Langerhans in the pancreas. It is initially synthesized as a single, inactive polypeptide precursor called proinsulin. During processing, a connecting peptide (C-peptide) is removed, leaving two polypeptide chains: the A chain (21 amino acids) and the B chain (30 amino acids). These two chains are held together by two interchain disulfide bridges (covalent bonds between sulfur atoms of cysteine residues), and there is also one intrachain disulfide bridge within the A chain.

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Question #1

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In the endocrine system, the hormone 'Oxytocin' is synthesized in the hypothalamus but is stored and released by the:

A. Posterior pituitary (Neurohypophysis)

B. Thyroid gland

C. Adrenal medulla

D. Anterior pituitary

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Correct Answer: Option A

Explanation:
Oxytocin (and ADH/vasopressin) are peptide hormones synthesized by the neurosecretory cells of the hypothalamus (supraoptic and paraventricular nuclei). They are transported down the axons of these neurons and stored in the nerve terminals of the posterior pituitary (neurohypophysis). Upon neural stimulation, they are released directly into the bloodstream from the posterior pituitary. The anterior pituitary synthesizes its own hormones.

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Question #2

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Consider statements about human nutrition: 1. Essential amino acids cannot be synthesized by the body. 2. Saturated fats are liquid at room temperature. 3. Dietary fiber aids in digestion. Which are correct?

A. 1, 2 and 3

B. 2 and 3 only

C. 1 and 3 only

D. 1 and 2 only

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Correct Answer: Option C

Explanation:
Essential amino acids (like lysine, tryptophan) cannot be synthesized by the human body and must be obtained through the diet. Dietary fiber (roughage) is indigestible plant material that adds bulk to stool, promotes peristalsis, and aids in digestion and preventing constipation. Saturated fats have no double bonds between carbon atoms, making them solid at room temperature (like butter); unsaturated fats are liquid (like oils). Thus, statements 1 and 3 are correct.

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Question #3

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The substance used to preserve dead biological specimens is:

A. Formalin

B. Alcohol

C. Acetone

D. Glycerin

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Correct Answer: Option A

Explanation:
Formalin (37-40% formaldehyde solution) is a common fixative and preservative for biological specimens, preventing decay by cross-linking proteins. Alcohol is also used but formalin is standard. Acetone is a solvent, glycerin a humectant.

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