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Digestion, circulation, respiration and excretion
9 MDCAT Biology questions with answers and explanations.
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Which enzyme in saliva begins the digestion of starch?
- 1 Pepsin
- 2 Salivary amylase
- 3 Lipase
- 4 Trypsin
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Correct answer: Salivary amylase
Salivary amylase breaks starch into maltose in the mouth. Pepsin works on proteins in the stomach.
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Which chamber of the heart pumps oxygenated blood to the body?
- 1 Right atrium
- 2 Right ventricle
- 3 Left atrium
- 4 Left ventricle
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Correct answer: Left ventricle
The left ventricle has the thickest wall and pushes blood into the aorta for the whole body.
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The functional unit of the kidney is the:
- 1 Neuron
- 2 Nephron
- 3 Alveolus
- 4 Villus
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Correct answer: Nephron
Each kidney has about a million nephrons, which filter blood and form urine.
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Gas exchange in the lungs takes place in the:
- 1 Bronchi
- 2 Trachea
- 3 Alveoli
- 4 Pleura
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Correct answer: Alveoli
Alveoli have very thin walls and a rich blood supply, so oxygen and carbon dioxide diffuse across them easily.
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Which vessel carries oxygenated blood from the lungs to the heart?
- 1 Pulmonary artery
- 2 Pulmonary vein
- 3 Vena cava
- 4 Aorta
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Correct answer: Pulmonary vein
The pulmonary vein is unusual because it carries oxygenated blood. It enters the left atrium.
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Which acid is secreted by the stomach to kill microbes and activate pepsinogen?
- 1 Sulphuric acid
- 2 Lactic acid
- 3 Hydrochloric acid
- 4 Nitric acid
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Correct answer: Hydrochloric acid
Parietal cells secrete hydrochloric acid, which gives the stomach a pH of about 2 and converts pepsinogen into pepsin.
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Most of the water in the glomerular filtrate is reabsorbed in the:
- 1 Proximal convoluted tubule
- 2 Collecting duct
- 3 Bowman's capsule
- 4 Loop of Henle only
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Correct answer: Proximal convoluted tubule
About two thirds of the filtered water is reabsorbed in the proximal convoluted tubule, together with glucose and salts.
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Which blood component is mainly responsible for clotting?
- 1 Red blood cells
- 2 Platelets
- 3 Lymphocytes
- 4 Plasma proteins only
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Correct answer: Platelets
Platelets stick together at a wound and release factors that start the clotting cascade.
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Bile is produced by the liver and stored in the:
- 1 Pancreas
- 2 Spleen
- 3 Gall bladder
- 4 Duodenum
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Correct answer: Gall bladder
The gall bladder stores and concentrates bile, then releases it into the duodenum to emulsify fats.