PPSC Everyday Science MCQs

Carbon dioxide is transported from tissues to the lungs.
It diffuses into alveoli and is exhaled.

Digestion breaks large food molecules into smaller units.
These nutrients can then be absorbed into blood or lymph.

The small intestine has villi that greatly increase surface area.
Most digested nutrients enter blood or lymph there.

The large intestine absorbs remaining water and salts.
It compacts undigested material into feces.

The heart has two atria and two ventricles.
The chambers separate oxygenated and deoxygenated blood.

Arteries carry blood away from the heart under pressure.
Most carry oxygenated blood, with pulmonary arteries as an exception.

Veins return blood to the heart.
Many contain valves that help prevent backflow.

Capillary walls are only one cell thick.
This allows diffusion of gases, nutrients, and wastes.

Photosynthesis stores light energy in glucose.
Oxygen is released as a by-product.

Red blood cells contain hemoglobin.
Hemoglobin binds and transports oxygen.

Carbon dioxide supplies carbon for glucose formation.
It enters leaves mainly through stomata.

White blood cells identify and attack pathogens.
Different types act through phagocytosis or immune responses.