Science MCQs

The coronary arteries branch off the aorta and supply oxygenated blood to the heart muscle (myocardium).

Enzymes are biological catalysts that speed up the metabolic reactions of respiration without being consumed.

Platelets are crucial for clotting. A deficiency (thrombocytopenia) leads to difficulty stopping bleeding.

Regular exercise is a protective factor that strengthens the heart and improves circulation, reducing heart attack risk.

The blue appearance is an optical effect. Light penetration and absorption by skin and blood make deoxygenated blood in deep veins appear blue.

Atherosclerosis is the buildup of plaques (cholesterol, fats) inside arteries, narrowing them and increasing the risk of heart attack and stroke.

Alveoli have extremely thin, one-cell-thick walls and are surrounded by a dense network of capillaries, creating a vast surface area for efficient diffusion.

CO2 produced in body cells diffuses into the blood, is carried to the lungs, diffuses into the alveoli, and is finally exhaled.

The pericardium is a double-layered sac that encloses the heart, providing protection and reducing friction as the heart beats.

Deoxygenated blood enters the right atrium, flows to the right ventricle and is then pumped to the lungs via the pulmonary artery.