All Free Biology MCQs with Answers

1911. _________ stimulates the production of gastric juice in the stomach:

• A. Gastrin
• B. Enterokinase
• C. Rennin
• D. None of these

Explanation: Gastrin is a hormone released mainly by the stomach lining that stimulates secretion of gastric juice, including hydrochloric acid and digestive enzymes. Students may choose rennin because it is also a stomach enzyme, but rennin digests milk protein and does not stimulate gastric secretion.

1912. One of the reasons why some people cough while eating a meal may be due to the improper movement of _______ :

• A. Larynx
• B. Diaphram
• C. Epiglottis
• D. None of these

Explanation: The epiglottis is a flap that covers the opening of the larynx during swallowing and directs food into the oesophagus. If it moves improperly, food may enter the airway and trigger coughing; students may choose the larynx because it is the airway structure involved, but the protective flap is the epiglottis.

1913. The small intestine has three parts. The first part is called________?

• A. Duodenum
• B. Oesophagus
• C. Larynx
• D. None of these

Explanation: The duodenum is the first part of the small intestine and receives bile and pancreatic juice for digestion. Students may choose the oesophagus because it is also part of the alimentary canal, but it lies before the stomach and is not part of the small intestine.

1914. the food ground in cockroach in______?

• A. mesentron
• B. crop
• C. gizzard
• D. intestine

Explanation: In a cockroach, the gizzard or proventriculus has a muscular wall and chitinous teeth that grind food mechanically. Students may choose the crop because it stores food, but storage is its main function rather than grinding.

1915. Typhoid is caused by_________?

• A. Salmonella typhi
• B. Hepatatis
• C. Bacillus
• D. None of the above

Explanation: Typhoid is caused by Salmonella typhi, a bacterium that commonly spreads through food or water contaminated with human waste. Students may choose “Bacillus” because it sounds like a bacterial name, but Bacillus is a bacterial genus, not the specific organism responsible for typhoid.

1916. Dysentery is a disease that can lead to severe diarrhea with mucus or blood in the feces caused by inflammation in?

• A. Stomach
• B. Small intestine
• C. Colon
• D. Liver

Explanation: Dysentery commonly involves inflammation of the colon, producing frequent stools that may contain mucus and blood. The small intestine may be associated with other diarrhoeal diseases, but the colon is the characteristic site described in this question.

1917. Pancreas is/are__________?

• A. Endocrine Gland
• B. Exocrine Gland
• C. Digestive Gland
• D. All of the above

Explanation: The pancreas has both exocrine and endocrine functions, and its exocrine secretions include digestive enzymes released into the small intestine. Its endocrine cells release hormones such as insulin, so it is correctly described by all three of the first classifications.

1918. The enzyme which is secreted by salivary gland is?

• A. Pepsin
• B. Ptyalin
• C. Lactalase
• D. Bile

Explanation: Salivary glands secrete ptyalin, also called salivary amylase, which begins the digestion of starch in the mouth. Pepsin acts in the stomach, bile is produced by the liver, and lactase is an intestinal enzyme, so they are not salivary secretions.

1919. Acid present in gastric juice is_________?

• A. Hydrochloric Acid
• B. Citric Acid
• C. Sulphuric Acid
• D. Acetic Acid

Explanation: The stomach lining secretes hydrochloric acid, which creates a strongly acidic medium for pepsin activity and helps kill many swallowed microorganisms. Citric acid is found mainly in citrus fruits, while sulphuric and acetic acids are not the normal gastric acid. Students may choose another familiar acid because they confuse acids found in foods with the acid in gastric juice.

1920. An adult human normally has______?

• A. 6 molar teeth
• B. 8 molar teeth
• C. 10 molar teeth
• D. 12 molar teeth

Explanation: An adult normally has 12 molars: 3 on each side of the upper jaw and 3 on each side of the lower jaw, including the wisdom teeth. Students may choose 8 because there are 8 premolars, or because wisdom teeth may be absent or removed, but the normal complete dentition has 12 molars.