All Free Biology MCQs with Answers

881. The posterior pituitary releases

• A. GH and TSH
• B. ADH and oxytocin
• C. ACTH and FSH
• D. Prolactin and LH

Explanation: The posterior pituitary stores and releases ADH and oxytocin, which are produced in the hypothalamus.

882. Goiter is caused by

• A. Excess iodine
• B. Iodine deficiency
• C. Excess calcium
• D. Vitamin D deficiency

Explanation: Iodine deficiency causes goiter (enlarged thyroid) as the gland tries to compensate for insufficient T3/T4 production.

883. Steroid hormones act by

• A. Binding cell surface receptors
• B. Binding intracellular receptors
• C. Opening ion channels
• D. Activating second messengers

Explanation: Steroid hormones (lipid-soluble) diffuse through membranes and bind intracellular receptors that regulate gene transcription.

884. Type 1 diabetes is caused by

• A. Insulin resistance
• B. Autoimmune destruction of beta cells
• C. Excess insulin
• D. Pituitary tumor

Explanation: Type 1 diabetes is an autoimmune disease where beta cells are destroyed, requiring insulin injections.

885. Calcitonin lowers blood calcium by

• A. Increasing bone resorption
• B. Decreasing bone resorption
• C. Increasing calcium absorption
• D. Decreasing calcium excretion

Explanation: Calcitonin from the thyroid inhibits osteoclasts, decreasing bone resorption and lowering blood calcium.

886. The stress hormone adrenaline causes all EXCEPT

• A. Increased heart rate
• B. Bronchodilation
• C. Glycogenolysis
• D. Decreased blood pressure

Explanation: Adrenaline increases (not decreases) blood pressure through vasoconstriction and increased cardiac output.

887. Pepsin digests

• A. Carbohydrates
• B. Proteins
• C. Fats
• D. Nucleic acids

Explanation: Pepsin is a protease that digests proteins into peptides in the acidic environment of the stomach.

888. Bile is produced by the

• A. Gall bladder
• B. Liver
• C. Pancreas
• D. Stomach

Explanation: Bile is produced by the liver, stored in the gall bladder, and released into the duodenum.

889. The function of bile salts is to

• A. Digest fats enzymatically
• B. Emulsify fats
• C. Absorb fatty acids
• D. Produce lipase

Explanation: Bile salts emulsify fats, breaking large fat droplets into smaller ones to increase surface area for lipase action.

890. Most absorption occurs in the

• A. Stomach
• B. Duodenum
• C. Ileum
• D. Colon

Explanation: Most nutrient absorption occurs in the ileum (small intestine), which has villi and microvilli for maximum surface area.