(a) In the process of respiration, state the function of alveoli.
(b) The rate of breathing in aquatic organisms is much faster than that in terrestrial organisms. Give reasons.
(c) Complete the following pathway showing the breakdown of glucose.

(a) Function of alveoli in respiration:

• Alveoli are tiny, balloon-like structures in the lungs where gaseous exchange occurs.
• They allow oxygen from inhaled air to diffuse into the blood and carbon dioxide from the blood to diffuse out into the air to be exhaled.

(b) Reason why breathing is faster in aquatic organisms:

• Water contains much less dissolved oxygen than air.
• To meet their oxygen demands, aquatic organisms like fish must breathe faster and pump more water over their gills to extract enough oxygen.

(c) Pathway showing the breakdown of glucose:

• Glucose (6-carbon molecule) → Pyruvate (3-carbon molecule) + Energy (in cytoplasm)

Then:

• In presence of oxygen (aerobic respiration, in mitochondria):
  Pyruvate → Carbon dioxide + Water + Energy
• In absence of oxygen (anaerobic respiration in muscle cells):
  Pyruvate → Lactic acid + Energy
• In absence of oxygen (anaerobic respiration in yeast):
  Pyruvate → Ethanol + Carbon dioxide + Energy