Which statement describes anaerobic respiration?
A) Anaerobic respiration in humans produces lactic acid and carbon dioxide.
B) Anaerobic respiration in yeast produces water and carbon dioxide.
C) Anaerobic respiration releases energy from glucose without using oxygen.
D) Anaerobic respiration releases more energy per glucose molecule than aerobic respiration.
▶️ Answer/Explanation
Ans: C
Option C is correct because anaerobic respiration is defined as the release of energy from glucose without oxygen. This occurs in both humans (lactic acid fermentation) and yeast (alcoholic fermentation).
Option A is incorrect because human anaerobic respiration produces lactic acid, not carbon dioxide.
Option B is incorrect because yeast anaerobic respiration produces ethanol and CO2, not water.
Option D is incorrect because aerobic respiration releases far more energy (36-38 ATP/glucose) than anaerobic respiration (2 ATP/glucose).
Thus, only C accurately describes anaerobic respiration.
Some yeast, sugar and water are mixed in a test-tube. The diagrams show the test-tube at the start and after one hour.
Which process causes this change?
A) growth
B) reproduction
C) respiration
D) sensitivity
▶️ Answer/Explanation
Ans: C
Yeast undergoes anaerobic respiration (fermentation) when mixed with sugar, producing carbon dioxide gas and ethanol. The observed bubbles or foam in the test-tube indicate gas release, confirming respiration (C).
Growth (A) and reproduction (B) are biological processes but do not directly cause gas production. Sensitivity (D) involves responses to stimuli, which is unrelated. Thus, the correct answer is C (Respiration).