Question 1

The gland that secretes melatonin and regulates the sleep-wake (diurnal) cycle is the:

Accepted Answer

Pineal gland. The pineal gland secretes melatonin, which maintains the body's circadian rhythm and sleep-wake cycle.

Question 2

The gland that plays a major role in the development of the immune system (T-lymphocytes) is the:

Accepted Answer

Thymus. The thymus secretes thymosins that promote differentiation of T-lymphocytes; it degenerates with age.

Question 3

The male sex hormones (androgens like testosterone) are secreted by the ______ of the testis:

Accepted Answer

Leydig (interstitial) cells. Leydig cells produce androgens (testosterone) that develop male secondary sexual characters.

Question 4

The hormones estrogen and progesterone are secreted mainly by the:

Accepted Answer

Ovary. The ovary secretes estrogen (follicle) and progesterone (corpus luteum), regulating the female reproductive cycle.

Question 5

Steroid hormones and thyroxine can enter the target cell and act by:

Accepted Answer

Binding intracellular receptors and regulating gene (DNA) transcription. Lipid-soluble hormones (steroids, thyroxine) cross the membrane, bind nuclear/cytoplasmic receptors and alter gene expression.

Question 6

Protein/peptide hormones like insulin act through the second-messenger mechanism because they:

Accepted Answer

Cannot enter the cell, so they bind surface receptors and generate second messengers (e.g. cAMP). Being water-soluble, peptide hormones bind membrane receptors and trigger intracellular second messengers to produce the response.

Question 7

The pineal gland secretes melatonin, whose principal role is the regulation of:

Accepted Answer

The 24-hour (diurnal) rhythms and the sleep-wake cycle. Melatonin from the pineal gland regulates the diurnal (circadian) rhythm of the body, including the sleep-wake cycle, besides influencing metabolism, pigmentation and the menstrual cycle.

Question 8

The peptide hormones thymosins, important for the differentiation of T-lymphocytes, are produced by the:

Accepted Answer

Thymus gland. Thymosins from the thymus promote differentiation of T-lymphocytes and thus cell-mediated immunity, also stimulating antibody production.

Question 9

In the male, the Leydig (interstitial) cells of the testis secrete androgens whose functions include:

Accepted Answer

Development of secondary sexual characters and stimulation of spermatogenesis. Testicular androgens (mainly testosterone) drive the development of male accessory sex organs and secondary sexual characters and stimulate spermatogenesis.

Question 10

During the second half of the menstrual cycle, progesterone secreted mainly by the corpus luteum functions to:

Accepted Answer

Maintain the uterine endometrium in readiness for/support of pregnancy. Progesterone from the corpus luteum supports pregnancy by maintaining the endometrium (and later acts on the mammary glands), while estrogen governs female secondary sexual characters.

Question 11

A hydrophilic peptide hormone binds its receptor on the target-cell membrane. The correct downstream sequence leading to the cellular response is:

Accepted Answer

Hormone–receptor binding → generation of second messenger (e.g. cAMP) → altered activity of intracellular enzymes → response. Peptide/protein hormones cannot cross the membrane, so binding to a surface receptor generates a second messenger such as cAMP, which changes intracellular enzyme activity to produce the response.

Question 12

Assertion (A): Steroid and thyroid hormones typically produce slower but longer-lasting effects than peptide hormones. Reason (R): They act by entering the cell and regulating gene expression, altering the amounts of specific proteins synthesised. Choose the correct option.

Accepted Answer

Both A and R are true and R is the correct explanation of A. Lipid-soluble steroid and thyroid hormones bind intracellular receptors and modulate gene transcription; making new proteins is slower to start but longer-lasting, so R correctly explains A.

Question 13

Match the gland (Column I) with its secretion (Column II):
(i) Pineal  (ii) Thymus  (iii) Ovary
(p) Estrogen  (q) Melatonin  (r) Thymosin

Accepted Answer

(i)-(q), (ii)-(r), (iii)-(p). The pineal secretes melatonin, the thymus secretes thymosins, and the ovary secretes estrogen (and progesterone).

Question 14

Which of the following statements about the hormone-receptor complex is INCORRECT?

Accepted Answer

Intracellular receptors for hormones are located on the outer surface of the plasma membrane. Intracellular receptors are located inside the cell (in the cytoplasm/nucleus), not on the membrane surface; the other statements are correct.

Question 15

The thymus gland gradually degenerates with age. A likely functional consequence of this involution in old age is:

Accepted Answer

Weakened immune responses due to reduced T-lymphocyte support. As the thymus involutes with age, thymosin output falls, weakening the production and support of T-lymphocytes and thus the immune response.

Question 16

Which of the following statements comparing the two major mechanisms of hormone action is/are correct?
(i) Peptide hormones generally use a membrane receptor and a second messenger.
(ii) Steroid hormones generally bind intracellular receptors and act on genes.
(iii) Thyroxine, being lipid-soluble, acts like a steroid rather than like a peptide hormone.

Accepted Answer

(i), (ii) and (iii). All three are correct: peptide hormones use surface receptors with second messengers, steroids use intracellular receptors regulating genes, and lipid-soluble thyroxine acts by the intracellular (steroid-like) route.

Question 17

Read the following statements about hormone action and choose the incorrect option: (i) Hormone-receptor complex formation leads to biochemical changes in the target tissue; (ii) Target tissue metabolism and physiological functions are regulated by hormones; (iii) Secondary messengers in turn regulate cellular metabolism.

Accepted Answer

None of the above (all the statements are correct). All three statements correctly describe hormone-receptor interaction and second-messenger action, so none is incorrect.

Question 18

Which of the following hormones does NOT interact with intracellular receptors?

Accepted Answer

Somatostatin. Steroid hormones act via intracellular receptors, but the peptide hormone somatostatin acts through membrane (cell-surface) receptors.

Question 19

The pineal gland is located on the:

Accepted Answer

Dorsal side of the forebrain. The pineal gland lies on the dorsal side of the forebrain.

Question 20

Which of the following functions are regulated by melatonin/the pineal gland? a. Defense capability b. Pigmentation c. Menstrual cycle d. Metabolism e. Diurnal (24-hour) rhythm f. Body temperature g. Sleep-wake cycle

Accepted Answer

a, b, c, d, e, f and g. Melatonin regulates the diurnal rhythm, sleep-wake cycle, body temperature, metabolism, pigmentation, menstrual cycle and defense capability.

Other Glands & Mechanism — NEET Biology MCQs with Solutions

Questions with solutions