(a) (i) What is respiration? (ii) In a tabular form, state four differences between gaseous exchange and aerobic respiration (b)(i) Explain the term residua...

(a)(i) Respiration

Respiration is the process by which food substances (mainly glucose) are oxidised within living cells to release energy (stored as ATP) needed for the activities of the organism, usually with the uptake of oxygen and release of carbon dioxide and water.

(a)(ii) Four differences between gaseous exchange and aerobic respiration

(b)(i) Residual air

Residual air is the volume of air that remains in the lungs and cannot be breathed out even after the most forceful expiration.

(b)(ii) Importance of residual air

It keeps the alveoli (air sacs) inflated so they do not collapse, and it allows continuous gaseous exchange between breaths, so oxygen is still absorbed into the blood even during expiration.

(c) Four characteristic features of respiratory structures

1. They have a large surface area for maximum gaseous exchange.
2. They are thin (one or few cells thick) for rapid diffusion of gases.
3. They are moist so that gases dissolve before diffusing.
4. They are well supplied with blood vessels (highly vascular) to maintain a steep diffusion gradient.

(d)(i) Oxygen debt

Oxygen debt is the extra amount of oxygen that the body needs to take in after vigorous exercise, to oxidise the lactic acid that accumulated in the muscles during anaerobic respiration.

(d)(ii) Three activities that can result in oxygen debt

• Sprinting / fast running (a race).
• Weight lifting / heavy physical work.
• Vigorous swimming or fast cycling.