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

What role does DNA play in anaerobic respiration?

1. It provides energy for respiration

2. It holds the genetic code for making the enzymes needed for respiration

3. It transports oxygen to cells

4. It assists in the breakdown of glucose

The correct answer is: It holds the genetic code for making the enzymes needed for respiration

DNA plays a crucial role in anaerobic respiration by holding the genetic code for synthesizing enzymes that are essential for the process. Enzymes act as biological catalysts, facilitating the chemical reactions needed to break down glucose and other substrates during respiration. In the absence of oxygen, organisms utilize anaerobic respiration pathways, such as fermentation, to extract energy from glucose. The enzymes specified by the DNA are responsible for converting pyruvate into ethanol or lactic acid, depending on the type of organism. While enzymes are critical for the anaerobic respiration process, energy is not supplied directly by DNA but rather through the metabolic breakdown of glucose. DNA also does not transport oxygen; this function is primarily performed by hemoglobin in blood. Additionally, while DNA contributes to the enzymes for glucose breakdown, it does not directly assist in the breakdown itself but rather provides the instructions for making those enzymes.