All Free Biology MCQs with Answers

571. The microscopic finger like projections of the epithelial cells of each villus are called

• A. microvilli
• B. villi
• C. cilia
• D. flagella

Explanation: Microvilli multiply the absorptive surface a further twenty times beyond the villi themselves. Cilia and flagella are motile structures, so the name similarity hides a different function.

572. Blood carrying the products of digestion from the intestine is delivered first to the

• A. heart
• B. kidneys
• C. lungs
• D. liver, by the hepatic portal vein

Explanation: The liver screens, stores and adjusts nutrients before they enter the general circulation, regulating glucose and detoxifying harmful substances. Sending blood straight to the heart would bypass this control.

573. Diarrhoea occurs when

• A. the large intestine absorbs too much water
• B. digestion proceeds too rapidly in the stomach
• C. the intestinal contents move too quickly for adequate water absorption
• D. the villi absorb too much glucose

Explanation: When contents rush through, the large intestine cannot reclaim enough water and the faeces stay liquid, risking dehydration. Too much absorption has the opposite effect, causing constipation.

574. Constipation results from

• A. very rapid peristalsis
• B. slow movement of contents through the large intestine with excess water absorption
• C. excess secretion of bile
• D. overactivity of the salivary glands

Explanation: The longer contents linger, the more water is reabsorbed and the harder and drier the faeces become. Fibre adds bulk that speeds transit, which is why roughage prevents it.

575. Marasmus, the wasting disease of starving children, is caused by a diet deficient in

• A. calories and protein overall
• B. vitamin C only
• C. iron only
• D. iodine only

Explanation: Marasmus reflects total starvation, with loss of muscle and fat, while kwashiorkor is protein deficiency with adequate calories, causing oedema. The two malnutrition syndromes are distinguished by exactly this point.

576. The taking of food into the body is called

• A. digestion
• B. assimilation
• C. absorption
• D. ingestion

Explanation: Ingestion is simply intake; digestion breaks food down, absorption moves the products into blood, and assimilation uses them in cells. Each step of nutrition has its own term.

577. The mucus secreted by the cells of the stomach wall serves mainly to

• A. digest cellulose
• B. kill every bacterium swallowed
• C. protect the stomach wall from acid and pepsin
• D. absorb glucose

Explanation: A layer of mucus shields the epithelium from hydrochloric acid and pepsin, which would otherwise digest the stomach itself. When this protection fails, ulcers can form.

578. The acidic chyme entering the duodenum is neutralised by

• A. hydrochloric acid
• B. bicarbonate present in the pancreatic juice and bile
• C. pepsin
• D. salivary amylase

Explanation: Pancreatic bicarbonate raises the pH to around 8, the alkaline range in which pancreatic and intestinal enzymes work. Acid from the stomach would inactivate them, so neutralisation is essential.

579. The semi fluid mass of partly digested food in the stomach is called

• A. chyme
• B. bolus
• C. faeces
• D. bile

Explanation: Churning mixes food with gastric juice to form chyme, which is released in small amounts into the duodenum. The bolus is the earlier stage, the swallowed lump from the mouth.

580. The soft mass of chewed food formed in the mouth and swallowed is called the

• A. chyme
• B. plaque
• C. calculus
• D. bolus

Explanation: The tongue shapes moistened, chewed food into a slippery bolus sized for swallowing. Chyme comes later, in the stomach, so order of appearance separates the two.