Important Questions Class 11 Biology Chapter 19 Chemical Coordination and Integration With Answers

Chemical coordination uses hormones to regulate body functions that need continuous control.
Endocrine glands, hormones, target tissues and receptors help maintain growth, metabolism, reproduction and homeostasis.

Hormones control many body functions slowly but continuously, making them essential for metabolism, growth, reproduction and homeostasis. Important Questions Class 11 Biology Chapter 19 help students prepare Chemical Coordination and Integration for CBSE 2026-27 school exams, NEET foundation practice and NCERT-based state board tests. This chapter includes endocrine glands, hypothalamus, pituitary hormones, pineal gland, thyroid hormones, parathyroid hormone, thymosins, adrenal hormones, insulin, glucagon, testosterone, estrogen, progesterone, gastrointestinal hormones and mechanism of hormone action.

Key Takeaways

• Endocrine Glands: Endocrine glands are ductless glands that release hormones directly into blood.
• Hormones: Hormones are non-nutrient chemicals that act as intercellular messengers in trace amounts.
• Glucose Balance: Insulin lowers blood glucose, while glucagon increases blood glucose.
• Hormone Action: Peptide hormones usually act through membrane receptors, while steroid hormones act through intracellular receptors.

Important Questions Class 11 Biology Chapter 19 Structure 2026

Important Questions Class 11 Biology Chapter 19 for CBSE 2026-27

This chapter becomes easier when students remember the gland, hormone, target and function together. CBSE questions often ask hormone deficiency, hormone excess, target gland and mechanism of action.

1. What is chemical coordination in Class 11 Biology?

Chemical coordination is the regulation and integration of body functions through hormones.

1. Neural coordination is fast but short-lived.
2. Nerve fibres do not reach every body cell.
3. Many cell functions need continuous regulation.
4. Hormones provide chemical coordination.

Final answer: Chemical coordination is hormone-based regulation of body functions.

2. Why is endocrine coordination needed if neural coordination exists?

Endocrine coordination is needed because neural coordination is rapid but short-lived and does not directly reach all cells.

1. Nerves provide point-to-point control.
2. Hormones provide chemical integration.
3. Hormones regulate distant target tissues.
4. Neural and endocrine systems work together.

Final fact: Neural and endocrine systems jointly regulate physiological functions.

3. What is the difference between neural and endocrine coordination?

Neural coordination is fast and short-lived, while endocrine coordination is chemical and longer-lasting.

Final fact: Both systems coordinate body functions together.

Endocrine Glands Class 11 Biology Questions

Endocrine glands release hormones without ducts. Their hormones reach target tissues through blood and regulate metabolism, growth, reproduction and homeostasis.

4. What are endocrine glands?

Endocrine glands are ductless glands that release hormones directly into the blood.

1. They lack ducts.
2. Their secretions are hormones.
3. Hormones travel through blood.
4. Hormones act on target organs or tissues.

Final answer: Endocrine glands are ductless hormone-secreting glands.

5. What are exocrine glands?

Exocrine glands release their secretions through ducts.

1. They have ducts.
2. Their secretions reach a body surface or cavity.
3. They differ from endocrine glands.

Final fact: Exocrine glands are duct-bearing glands.

6. What is a hormone Class 11 Biology?

A hormone is a non-nutrient chemical that acts as an intercellular messenger and is produced in trace amounts.

1. Hormones are chemical messengers.
2. They act between cells.
3. They are needed in small quantities.
4. They regulate target tissue functions.

Final answer: Hormones are intercellular chemical messengers.

7. What is the difference between endocrine and exocrine glands?

Endocrine glands are ductless, while exocrine glands have ducts.

Final fact: Endocrine glands release hormones directly into blood.

Human Endocrine System Class 11 Biology Questions

The human endocrine system includes organised endocrine glands and hormone-secreting tissues. Heart, kidney and gastrointestinal tract also produce hormones.

8. Name the major endocrine glands in humans.

The major endocrine glands are pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus and gonads.

Organised endocrine bodies:

1. Pituitary.
2. Pineal.
3. Thyroid.
4. Adrenal.
5. Pancreas.
6. Parathyroid.
7. Thymus.
8. Testis in males.
9. Ovary in females.

Final fact: The endocrine system also includes hormone-producing tissues in heart, kidney and gastrointestinal tract.

9. Which non-endocrine organs produce hormones?

Heart, kidney, gastrointestinal tract and liver can produce hormone-like chemical messengers.

Examples:

1. Heart secretes atrial natriuretic factor.
2. Kidney secretes erythropoietin.
3. Gastrointestinal tract secretes gastrin, secretin, CCK and GIP.

Final answer: Several organs apart from endocrine glands also secrete hormones.

Hypothalamus Hormones Class 11 Biology Questions

The hypothalamus links the nervous system with the endocrine system. It regulates pituitary hormone secretion through releasing and inhibiting hormones.

10. What is the role of hypothalamus in endocrine control?

Hypothalamus regulates the synthesis and secretion of pituitary hormones.

1. It is the basal part of diencephalon in forebrain.
2. It contains neurosecretory cells called nuclei.
3. It secretes releasing hormones.
4. It secretes inhibiting hormones.
5. It controls anterior pituitary through portal circulation.

Final answer: Hypothalamus controls pituitary hormone release.

11. What are releasing and inhibiting hormones?

Releasing hormones stimulate pituitary secretion, while inhibiting hormones suppress pituitary secretion.

1. GnRH stimulates gonadotrophin release.
2. Somatostatin inhibits growth hormone release.
3. These hormones originate in hypothalamic neurons.
4. They reach anterior pituitary through portal circulation.

Final fact: Hypothalamic hormones regulate anterior pituitary.

12. What is GnRH?

GnRH is gonadotrophin releasing hormone secreted by the hypothalamus.

1. It stimulates pituitary synthesis of gonadotrophins.
2. It supports release of LH and FSH.
3. It links hypothalamus with reproductive hormone control.

Final answer: GnRH stimulates gonadotrophin release.

13. What is somatostatin?

Somatostatin is a hypothalamic inhibiting hormone that suppresses growth hormone release.

1. It is produced by hypothalamus.
2. It inhibits GH release from pituitary.
3. It is an example of inhibiting hormone.

Final fact: Somatostatin inhibits growth hormone secretion.

Pituitary Gland Class 11 Biology Questions

The pituitary gland is connected to the hypothalamus and controls many other endocrine glands. Its anterior and posterior parts differ in hormone production and release.

14. Where is the pituitary gland located?

Pituitary gland is located in a bony cavity called sella tursica and is attached to the hypothalamus by a stalk.

1. It lies below the hypothalamus.
2. It has anatomical divisions.
3. It is regulated by hypothalamus.

Final answer: Pituitary gland lies in sella tursica.

15. What are adenohypophysis and neurohypophysis?

Adenohypophysis is the anterior pituitary part, while neurohypophysis is the posterior pituitary part.

1. Adenohypophysis includes pars distalis and pars intermedia.
2. Pars distalis is commonly called anterior pituitary.
3. Neurohypophysis is also called pars nervosa.
4. Neurohypophysis stores and releases hypothalamic hormones.

Final fact: Posterior pituitary stores and releases oxytocin and vasopressin.

16. Name the hormones secreted by anterior pituitary.

Anterior pituitary produces GH, PRL, TSH, ACTH, LH and FSH.

Hormones:

1. Growth hormone or GH.
2. Prolactin or PRL.
3. Thyroid stimulating hormone or TSH.
4. Adrenocorticotrophic hormone or ACTH.
5. Luteinizing hormone or LH.
6. Follicle stimulating hormone or FSH.

Final answer: Pars distalis secretes six major hormones.

17. What is melanocyte stimulating hormone?

Melanocyte stimulating hormone acts on melanocytes and regulates skin pigmentation.

1. It is secreted by pars intermedia.
2. Melanocytes contain melanin.
3. It regulates pigmentation.
4. In humans, pars intermedia is almost merged with pars distalis.

Final fact: MSH regulates pigmentation of skin.

18. What are the hormones of posterior pituitary?

Posterior pituitary stores and releases oxytocin and vasopressin.

1. These hormones are synthesised by hypothalamus.
2. They are transported axonally to neurohypophysis.
3. Neurohypophysis releases them into blood.

Final answer: Posterior pituitary releases oxytocin and vasopressin.

Pituitary Hormones Class 11 Biology Questions With Answers

Pituitary hormones regulate growth, lactation, thyroid activity, adrenal cortex activity and gonadal functions. They are commonly tested through matching questions.

19. What is the function of growth hormone?

Growth hormone stimulates body growth and somatic tissue development.

1. Excess GH in children causes gigantism.
2. Low GH in childhood causes pituitary dwarfism.
3. Excess GH in adults causes acromegaly.

Final answer: GH regulates body growth.

20. What are gigantism, dwarfism and acromegaly?

Gigantism, dwarfism and acromegaly are disorders linked with abnormal GH secretion.

1. Over-secretion of GH in children causes gigantism.
2. Low GH secretion causes pituitary dwarfism.
3. Excess GH in adults causes acromegaly.
4. Acromegaly causes severe disfigurement, especially of face.

Final fact: GH imbalance affects body growth.

21. What is the function of prolactin?

Prolactin regulates growth of mammary glands and formation of milk.

1. It acts on mammary glands.
2. It supports milk production.
3. It is secreted by anterior pituitary.

Final answer: Prolactin supports lactation.

22. What are the functions of TSH and ACTH?

TSH stimulates thyroid hormones, while ACTH stimulates adrenal cortex glucocorticoids.

1. TSH acts on thyroid gland.
2. It stimulates T₃ and T₄ secretion.
3. ACTH acts on adrenal cortex.
4. It stimulates glucocorticoid secretion.

Final fact: TSH and ACTH are trophic hormones.

23. What are gonadotrophins?

LH and FSH are called gonadotrophins because they stimulate gonadal activity.

1. LH acts on testes and ovaries.
2. FSH acts on testes and ovaries.
3. In males, LH stimulates androgen secretion.
4. In females, LH induces ovulation.
5. FSH supports spermatogenesis and follicle growth.

Final answer: LH and FSH are gonadotrophic hormones.

24. What is the function of oxytocin?

Oxytocin acts on smooth muscles and stimulates contraction.

1. It causes vigorous uterine contraction during childbirth.
2. It helps milk ejection from mammary gland.
3. It is released by posterior pituitary.

Final fact: Oxytocin supports parturition and milk ejection.

25. What is vasopressin or ADH?

Vasopressin or ADH acts on kidney and reduces water loss through urine.

1. It stimulates reabsorption of water.
2. It stimulates electrolyte reabsorption in distal tubules.
3. It reduces diuresis.
4. ADH deficiency causes diabetes insipidus.

Final answer: ADH conserves body water.

26. What is diabetes insipidus?

Diabetes insipidus occurs when ADH synthesis or release is impaired.

1. Kidney cannot conserve enough water.
2. Excess water loss occurs.
3. Dehydration can result.
4. It is linked with vasopressin deficiency or impairment.

Final fact: Diabetes insipidus is related to ADH.

Pineal Gland Class 11 Biology Questions

Pineal gland controls body rhythms through melatonin. It is important for sleep-wake cycle and 24-hour rhythm questions.

27. Where is pineal gland located and what does it secrete?

Pineal gland is located on the dorsal side of forebrain and secretes melatonin.

1. It is an endocrine gland.
2. It secretes melatonin.
3. Melatonin regulates biological rhythms.

Final answer: Pineal gland secretes melatonin.

28. What is the function of melatonin?

Melatonin regulates the 24-hour diurnal rhythm of the body.

1. It helps maintain sleep-wake cycle.
2. It helps regulate body temperature rhythm.
3. It influences metabolism.
4. It influences pigmentation.
5. It affects menstrual cycle and defence capability.

Final fact: Melatonin helps regulate circadian rhythm.

Thyroid Hormones Class 11 Biology Questions

Thyroid hormones regulate basal metabolic rate, RBC formation and metabolism of carbohydrates, proteins and fats. Iodine is essential for thyroid hormone synthesis.

29. Describe the structure of thyroid gland.

Thyroid gland has two lobes on either side of trachea connected by isthmus.

1. It contains follicles and stromal tissues.
2. Follicular cells enclose a cavity.
3. Follicular cells synthesise T₃ and T₄.

Final answer: Thyroid gland is bilobed and lies beside the trachea.

30. Name the thyroid hormones.

Thyroid follicular cells synthesise thyroxine or T₄ and triiodothyronine or T₃.

1. T₄ is tetraiodothyronine or thyroxine.
2. T₃ is triiodothyronine.
3. Iodine is essential for their synthesis.

Final fact: T₃ and T₄ are iodine-containing hormones.

31. What are the functions of thyroid hormones?

Thyroid hormones regulate basal metabolic rate, RBC formation and metabolism of carbohydrates, proteins and fats.

1. They regulate BMR.
2. They support red blood cell formation.
3. They control carbohydrate metabolism.
4. They control protein metabolism.
5. They control fat metabolism.
6. They influence water and electrolyte balance.

Final answer: Thyroid hormones regulate metabolism and development.

32. What is goitre?

Goitre is enlargement of thyroid gland commonly caused by iodine deficiency.

1. Iodine is needed for thyroid hormone synthesis.
2. Iodine deficiency causes hypothyroidism.
3. Thyroid gland enlarges.

Final fact: Iodine deficiency can cause goitre.

33. What is cretinism?

Cretinism is defective development in a baby caused by hypothyroidism during pregnancy.

Features may include:

1. Stunted growth.
2. Mental retardation.
3. Low intelligence quotient.
4. Abnormal skin.
5. Deaf-mutism.

Final answer: Cretinism occurs due to maternal hypothyroidism during pregnancy.

34. What is hyperthyroidism?

Hyperthyroidism is increased synthesis and secretion of thyroid hormones above normal levels.

1. It may occur due to thyroid cancer.
2. It may occur due to nodules of thyroid gland.
3. It affects body physiology.
4. Exophthalmic goitre is a form of hyperthyroidism.

Final fact: Hyperthyroidism increases thyroid hormone action.

35. What is exophthalmic goitre?

Exophthalmic goitre is a form of hyperthyroidism also called Graves’ disease.

Features:

1. Enlarged thyroid gland.
2. Protrusion of eyeballs.
3. Increased basal metabolic rate.
4. Weight loss.

Final answer: Exophthalmic goitre is Graves’ disease.

36. What is thyrocalcitonin?

Thyrocalcitonin is a protein hormone secreted by thyroid gland that regulates blood calcium levels.

1. It is also called TCT.
2. It helps regulate Ca²⁺ levels.
3. It works with parathyroid hormone in calcium balance.

Final fact: TCT helps calcium homeostasis.

Parathyroid Hormone Class 11 Biology Questions

Parathyroid hormone increases blood Ca²⁺. It works with thyrocalcitonin to maintain calcium balance.

37. Where are parathyroid glands located?

Four parathyroid glands are present on the back side of thyroid gland.

1. One pair occurs in each thyroid lobe.
2. They secrete parathyroid hormone.
3. Their secretion depends on blood Ca²⁺ levels.

Final answer: Parathyroid glands lie behind thyroid gland.

38. What is the function of parathyroid hormone?

Parathyroid hormone increases Ca²⁺ levels in blood.

1. It stimulates bone resorption.
2. It stimulates Ca²⁺ reabsorption by renal tubules.
3. It increases Ca²⁺ absorption from digested food.
4. It is a hypercalcemic hormone.

Final fact: PTH increases blood Ca²⁺.

39. Why is PTH called hypercalcemic hormone?

PTH is called hypercalcemic hormone because it increases blood Ca²⁺ levels.

1. It releases calcium from bones.
2. It reduces calcium loss through kidney.
3. It increases calcium absorption from food.

Final answer: PTH raises blood calcium concentration.

Thymus Class 11 Biology Questions

Thymus supports immune development. It becomes weaker in old age, reducing immune response.

40. Where is thymus located?

Thymus is a lobular gland located between lungs behind sternum on the ventral side of aorta.

1. It is part of the endocrine system.
2. It also supports immune function.
3. It secretes thymosins.

Final answer: Thymus lies behind sternum between the lungs.

41. What are thymosins?

Thymosins are peptide hormones secreted by thymus.

1. They help differentiation of T-lymphocytes.
2. They support cell-mediated immunity.
3. They promote antibody production.
4. They support humoral immunity.

Final fact: Thymosins help immune system development.

42. Why does immunity become weak in old age?

Immunity becomes weak in old age partly because thymus degenerates and thymosin production decreases.

1. Thymus reduces in function with age.
2. Thymosin production decreases.
3. Immune responses become weaker.

Final answer: Thymus degeneration weakens immune response in old individuals.

Adrenal Gland Hormones Class 11 Biology Questions

Adrenal gland has two parts: adrenal medulla and adrenal cortex. Medulla releases emergency hormones, while cortex releases corticoids.

43. Where are adrenal glands located?

One adrenal gland is located above each kidney.

1. Humans have one pair of adrenal glands.
2. Each gland has adrenal medulla.
3. Each gland has adrenal cortex.

Final fact: Adrenal glands sit above kidneys.

44. What are adrenal medulla hormones?

Adrenal medulla secretes adrenaline and noradrenaline.

1. Adrenaline is also called epinephrine.
2. Noradrenaline is also called norepinephrine.
3. These hormones are catecholamines.
4. They are emergency hormones.

Final answer: Adrenal medulla secretes fight-or-flight hormones.

45. Why are adrenaline and noradrenaline called emergency hormones?

Adrenaline and noradrenaline are called emergency hormones because they are secreted rapidly during stress and emergency.

Effects:

1. Increased alertness.
2. Pupil dilation.
3. Piloerection.
4. Sweating.
5. Increased heartbeat.
6. Increased strength of heart contraction.
7. Increased respiration rate.
8. Breakdown of glycogen.

Final fact: They prepare the body for fight or flight.

46. What are adrenal cortex hormones?

Adrenal cortex secretes corticoids such as glucocorticoids and mineralocorticoids.

1. Glucocorticoids regulate carbohydrate metabolism.
2. Cortisol is the main glucocorticoid.
3. Mineralocorticoids regulate water and electrolyte balance.
4. Aldosterone is the main mineralocorticoid.

Final answer: Adrenal cortex secretes cortisol and aldosterone.

47. What is the function of cortisol?

Cortisol stimulates gluconeogenesis, lipolysis and proteolysis.

1. It affects carbohydrate metabolism.
2. It supports cardiovascular and kidney functions.
3. It has anti-inflammatory action.
4. It suppresses immune response.
5. It stimulates RBC production.

Final fact: Cortisol is the main glucocorticoid.

48. What is the function of aldosterone?

Aldosterone maintains electrolytes, body fluid volume, osmotic pressure and blood pressure.

1. It acts mainly on renal tubules.
2. It stimulates Na⁺ and water reabsorption.
3. It promotes K⁺ and phosphate ion excretion.

Final answer: Aldosterone regulates salt and water balance.

49. What is Addison’s disease?

Addison’s disease occurs due to underproduction of adrenal cortex hormones.

1. Carbohydrate metabolism gets altered.
2. Acute weakness occurs.
3. Fatigue develops.

Final fact: Adrenal cortex hormone deficiency causes Addison’s disease.

Insulin and Glucagon Class 11 Biology Questions

Pancreas is both exocrine and endocrine. Its islets of Langerhans secrete insulin and glucagon to maintain blood glucose homeostasis.

50. Why is pancreas called a composite gland?

Pancreas is called a composite gland because it acts as both exocrine and endocrine gland.

1. Exocrine pancreas secretes digestive enzymes.
2. Endocrine pancreas has islets of Langerhans.
3. Islets secrete insulin and glucagon.

Final answer: Pancreas has both exocrine and endocrine functions.

51. What are islets of Langerhans?

Islets of Langerhans are endocrine cell clusters in pancreas.

1. They form only 1-2 percent of pancreatic tissue.
2. A normal pancreas has about 1-2 million islets.
3. α-cells secrete glucagon.
4. β-cells secrete insulin.

Final fact: Islets of Langerhans form endocrine pancreas.

52. What is the function of glucagon?

Glucagon increases blood glucose level and is called a hyperglycemic hormone.

1. It acts mainly on hepatocytes.
2. It stimulates glycogenolysis.
3. It stimulates gluconeogenesis.
4. It reduces cellular glucose uptake and use.

Final answer: Glucagon raises blood sugar.

53. What is the function of insulin?

Insulin lowers blood glucose level and supports glucose homeostasis.

1. It acts mainly on hepatocytes and adipocytes.
2. It enhances cellular glucose uptake.
3. It enhances glucose utilisation.
4. It stimulates glycogenesis.
5. It causes hypoglycemia.

Final fact: Insulin lowers blood sugar.

54. Differentiate between insulin and glucagon.

Insulin lowers blood glucose, while glucagon raises blood glucose.

Final fact: Insulin and glucagon jointly maintain glucose homeostasis.

55. What is diabetes mellitus?

Diabetes mellitus is a complex disorder caused by prolonged hyperglycemia.

1. It is associated with glucose loss through urine.
2. It may form harmful ketone bodies.
3. It can be treated with insulin therapy in diabetic patients.

Final answer: Diabetes mellitus is linked with insulin deficiency or insulin resistance.

Testis and Ovary Hormones Class 11 Biology Questions

Gonads act as primary sex organs and endocrine glands. Testis secretes androgens, while ovary secretes estrogen and progesterone.

56. What are the endocrine functions of testis?

Testis secretes androgens, mainly testosterone, from Leydig cells.

1. Testis is present in scrotal sac.
2. It acts as primary sex organ.
3. It acts as endocrine gland.
4. Leydig cells occur in intertubular spaces.

Final fact: Testosterone is the main testicular androgen.

57. What are the functions of androgens?

Androgens regulate male accessory sex organs, secondary sex characters and spermatogenesis.

1. They regulate epididymis, vas deferens and seminal vesicles.
2. They support prostate gland and urethra function.
3. They stimulate facial and axillary hair growth.
4. They deepen voice.
5. They stimulate spermatogenesis.
6. They influence male sexual behaviour.

Final answer: Androgens control male reproductive development and function.

58. What are the endocrine functions of ovary?

Ovary secretes estrogen and progesterone and produces one ovum during each menstrual cycle.

1. Growing ovarian follicles secrete estrogen.
2. Corpus luteum secretes progesterone.
3. Ovary is the primary female sex organ.

Final fact: Ovary produces ova and steroid hormones.

59. What are the functions of estrogen?

Estrogen stimulates female secondary sex organs, secondary sex characters and mammary gland development.

1. It supports growth of female reproductive organs.
2. It supports growing ovarian follicles.
3. It causes female secondary sex characters.
4. It supports mammary gland development.
5. It regulates female sexual behaviour.

Final answer: Estrogen supports female reproductive development.

60. What are the functions of progesterone?

Progesterone supports pregnancy and mammary gland development.

1. It is secreted mainly by corpus luteum.
2. It supports pregnancy.
3. It stimulates alveoli formation in mammary glands.
4. It stimulates milk secretion.

Final fact: Progesterone is a progestational hormone.

Hormones of Heart, Kidney and Gastrointestinal Tract Class 11 Biology

Some organs not usually called endocrine glands also secrete hormones. These hormones regulate blood pressure, RBC formation and digestion.

61. What hormone is secreted by heart?

Atrial wall of heart secretes atrial natriuretic factor or ANF.

1. ANF is a peptide hormone.
2. It is secreted when blood pressure increases.
3. It causes blood vessel dilation.
4. It decreases blood pressure.

Final answer: ANF lowers blood pressure.

62. What hormone is secreted by kidney?

Juxtaglomerular cells of kidney secrete erythropoietin.

1. Erythropoietin is a peptide hormone.
2. It stimulates erythropoiesis.
3. Erythropoiesis means RBC formation.

Final fact: Kidney produces erythropoietin.

63. Name the major gastrointestinal hormones.

The major gastrointestinal hormones are gastrin, secretin, cholecystokinin and gastric inhibitory peptide.

1. Gastrin.
2. Secretin.
3. Cholecystokinin or CCK.
4. Gastric inhibitory peptide or GIP.

Final answer: G-I tract secretes four major peptide hormones.

64. What are the functions of gastrin, secretin, CCK and GIP?

Gastrin stimulates gastric secretion, secretin stimulates bicarbonate secretion, CCK stimulates pancreatic enzymes and bile juice, and GIP inhibits gastric secretion and motility.

Final fact: G-I hormones regulate digestion.

Mechanism of Hormone Action Class 11 Biology Questions

Hormones act only on target tissues because target cells have specific receptors. Hormone-receptor binding produces biochemical and physiological effects.

65. What are hormone receptors?

Hormone receptors are specific proteins in target tissues that bind particular hormones.

1. Receptors may be on cell membrane.
2. Receptors may be inside target cells.
3. Each receptor is specific to one hormone.
4. Hormone binding forms hormone-receptor complex.

Final answer: Hormone receptors make target tissue response specific.

66. What is hormone-receptor complex?

Hormone-receptor complex forms when a hormone binds to its specific receptor.

1. It triggers biochemical changes.
2. It regulates target tissue metabolism.
3. It changes physiological function.

Final fact: Hormone-receptor complex starts hormone action.

67. What are membrane-bound receptors and intracellular receptors?

Membrane-bound receptors are present on target cell membrane, while intracellular receptors are present inside target cells.

Final fact: Receptor location depends on hormone type.

68. Classify hormones based on chemical nature.

Hormones are classified as peptide/protein hormones, steroids, iodothyronines and amino acid derivatives.

1. Peptide, polypeptide and protein hormones: insulin, glucagon, pituitary hormones, hypothalamic hormones.
2. Steroids: cortisol, testosterone, estradiol and progesterone.
3. Iodothyronines: thyroid hormones.
4. Amino acid derivatives: epinephrine.

Final answer: Hormones differ by chemical nature.

69. How do peptide hormones act?

Peptide hormones act through membrane-bound receptors and second messengers.

1. They bind receptors on the target cell membrane.
2. They usually do not enter the cell.
3. Second messengers are generated.
4. cAMP, IP₃ and Ca²⁺ can act as second messengers.
5. Cellular metabolism changes.

Final fact: Peptide hormones commonly use second messengers.

70. How do steroid hormones act?

Steroid hormones act through intracellular receptors and regulate gene expression.

1. Steroid hormones enter target cells.
2. They bind intracellular receptors.
3. Hormone-receptor complex interacts with genome.
4. Gene expression changes.
5. Physiological and developmental effects appear.

Final answer: Steroid hormones regulate chromosome function and gene expression.

Class 11 Biology Chemical Coordination and Integration Questions With Answers for Board Practice

NCERT exercise questions often test gland-hormone matching, deficiency disorders and hormone examples. These answers keep the hormone and function together.

71. List hormones secreted by thyroid, parathyroid and pancreas.

Thyroid secretes T₃, T₄ and TCT; parathyroid secretes PTH; pancreas secretes insulin and glucagon.

1. Thyroid: thyroxine or T₄, triiodothyronine or T₃, thyrocalcitonin.
2. Parathyroid: parathyroid hormone.
3. Pancreas: insulin and glucagon.

Final answer: These glands regulate metabolism, calcium and glucose.

72. Give one hyperglycemic and one hypoglycemic hormone.

Glucagon is a hyperglycemic hormone, while insulin is a hypoglycemic hormone.

1. Glucagon raises blood glucose.
2. Insulin lowers blood glucose.
3. Both are secreted by pancreas.

Final fact: Insulin and glucagon have opposite effects on blood glucose.

73. Give one hypercalcemic hormone.

Parathyroid hormone is a hypercalcemic hormone.

1. It increases Ca²⁺ in blood.
2. It stimulates bone resorption.
3. It increases calcium reabsorption by kidneys.

Final answer: PTH is hypercalcemic.

74. Give examples of gonadotrophic hormones.

LH and FSH are gonadotrophic hormones.

1. LH stimulates gonadal activity.
2. FSH stimulates gonadal activity.
3. Both are secreted by anterior pituitary.

Final fact: LH and FSH act on gonads.

75. Which hormone deficiency causes diabetes mellitus?

Insulin deficiency or insulin resistance causes diabetes mellitus.

1. Blood glucose remains high.
2. Glucose may be lost through urine.
3. Ketone bodies may form.

Final answer: Diabetes mellitus is linked with insulin.

76. Which hormone deficiency causes goitre?

Iodine deficiency reduces thyroid hormone synthesis and can cause goitre.

1. Iodine is essential for T₃ and T₄ synthesis.
2. Deficiency causes hypothyroidism.
3. Thyroid gland enlarges.

Final fact: Goitre is linked with iodine deficiency and hypothyroidism.

77. Match T₄, PTH, GnRH and LH with their glands.

T₄ is from thyroid, PTH is from parathyroid, GnRH is from hypothalamus, and LH is from pituitary.

Final answer: This matching follows NCERT endocrine gland-hormone pairs.

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