OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the equation for anaerobic respiration in plants and fungi?

1. Glucose + Oxygen --> Carbon Dioxide + Water

2. Glucose + Ethanol --> Carbon Dioxide

3. Glucose --> Ethanol + Carbon Dioxide

4. Glucose --> Lactic Acid

The correct answer is: Glucose --> Ethanol + Carbon Dioxide

The equation for anaerobic respiration in plants and fungi involves the conversion of glucose into ethanol and carbon dioxide. This process occurs when oxygen is not available, allowing these organisms to generate energy through fermentation. During anaerobic respiration, glucose is broken down without oxygen, resulting in the production of ethanol (alcohol) and carbon dioxide as byproducts. This is particularly significant in yeast, which undergoes alcoholic fermentation — a key process in brewing and baking. The generation of carbon dioxide is also crucial in these processes, as it causes dough to rise and contributes to the carbonation of beverages. In contrast, the other options reference different processes or conditions. For example, the first option describes aerobic respiration which requires oxygen. The second option is misleading as it incorrectly implies that glucose combines with ethanol, rather than producing it. The fourth option refers to lactic acid fermentation, which typically occurs in animal cells (including human muscle cells) when oxygen is scarce, not in plants and fungi. Thus, the equation 'Glucose --> Ethanol + Carbon Dioxide' accurately represents the anaerobic respiration that occurs in plants and fungi.