All Free Biology MCQs with Answers

1531. Which one forms the raw material for coenzymes_______________________?

• A. Vitamins
• B. Carbohydrates
• C. Proteins
• D. Metals

Explanation: Many coenzymes are derived from vitamins, especially B-group vitamins, which are converted into active coenzyme forms that carry electrons or chemical groups. The likely alternative is metals because some cofactors are metal ions, but metals are inorganic activators or cofactors rather than the raw material for most coenzymes.

1532. Enzymes __________________ the activation energy of a chemical reaction?

• A. Increases
• B. Decreases
• C. Does not effect
• D. Increases or decreases depending upon individual enzyme

Explanation: Enzymes decrease activation energy by providing an alternative reaction pathway, allowing more molecules to react at a given temperature. A student may choose d because enzymes can affect reaction rates in different ways, but catalysts do not increase activation energy, and the net enzyme effect is its reduction.

1533. enzyme is_____________?

• A. bio catalyst
• B. hormone
• C. Gland
• D. None of these

Explanation: An enzyme is a biological catalyst, meaning it speeds up a biochemical reaction by lowering its activation energy without being permanently consumed. Students may choose hormone because both regulate body processes, but hormones act as chemical messengers and do not necessarily catalyse reactions.

1534. In animals coordination is achieved by means of?

• A. Nervous system
• B. Endocrine system
• C. Respiratory system
• D. Both A and B

Explanation: Animals coordinate body activities through both the nervous system, which uses rapid electrical signals, and the endocrine system, which uses hormones carried in the blood. Choosing only the nervous system overlooks hormonal coordination, making option a the likely distractor.

1535. The hormone that causes the decrease in blood sugar level is called:____________?

• A. Glucagon
• B. Insulin
• C. Gastrin
• D. TSH (Thyroid Stimulation Hormone)

Explanation: Insulin lowers blood glucose by promoting glucose uptake by cells and its storage as glycogen in the liver and muscles. Students may choose glucagon because it is also a pancreatic hormone, but glucagon raises blood glucose rather than decreasing it.

1536. Acromegaly is caused due to oversecretion of____________?

• A. STH
• B. TSH
• C. ACTH
• D. Thyroxin

Explanation: Acromegaly results from excess secretion of somatotropic hormone, also called growth hormone or STH, after the growth plates have closed. Students may choose thyroxin because it affects body growth and metabolism, but excess thyroxin causes hyperthyroid symptoms rather than acromegaly.

1537. Secretin is secreted when _________ touches alimentary canal.

• A. Acidic
• B. Basic
• C. Neutral
• D. All of these

Explanation: Secretin is released by the duodenal mucosa when acidic chyme from the stomach enters the small intestine, and it stimulates bicarbonate secretion to neutralise that acid. Students may choose basic because bicarbonate is involved in the response, but the trigger is acidic chyme, not a basic substance.

1538. Which of the following cells secrete insulin?

• A. Alpha cells
• B. Delta cells
• C. Nerve cells
• D. Beta cells

Explanation: Beta cells in the islets of Langerhans secrete insulin, which lowers blood glucose by promoting glucose uptake and storage. Alpha cells secrete glucagon, while delta cells secrete somatostatin. Students may choose alpha cells because they are also pancreatic endocrine cells involved in glucose regulation, but their hormone has the opposite main effect.

1539. Which of following is a tiny gland?

• A. Thyroid
• B. Pancrease
• C. Pineal
• D. Pituitary

Explanation: The pineal gland is a very small endocrine gland that secretes melatonin and helps regulate biological rhythms such as the sleep-wake cycle. Students may choose the pituitary because it is often called the master gland, but it is not the tiny gland referred to here.

1540. Pineal gland situated in________?

• A. Brain
• B. Neck
• C. Stomach
• D. Above kideys

Explanation: The pineal gland lies deep within the brain, near the roof of the third ventricle, where it releases melatonin. Students may choose the neck because the thyroid and parathyroid glands are located there, but the pineal gland is a brain structure.