Which statement best describes anaerobic metabolism?

Which statement best describes anaerobic metabolism?

• A. Breakdown of proteins with oxygen
• B. Breakdown of fats with oxygen
• C. Breakdown of glycogen with oxygen
• D. Breakdown of glycogen without oxygen

Answer: (D)

Anaerobic metabolism means producing energy without using oxygen. In muscles, this mainly occurs through glycolysis starting from glycogen, where glycogen is broken down to glucose-6-phosphate and then to pyruvate. When oxygen is scarce, pyruvate is converted to lactate to regenerate NAD+, allowing glycolysis to continue and ATP to be produced quickly. This setup explains why the best description is breakdown of glycogen without oxygen. It reflects rapid, short‑term energy production that doesn’t rely on the mitochondrial oxidative system. The other ideas involve substrates or conditions that require oxygen, or describe aerobic pathways, so they don’t fit anaerobic metabolism as closely.

Anaerobic metabolism means producing energy without using oxygen. In muscles, this mainly occurs through glycolysis starting from glycogen, where glycogen is broken down to glucose-6-phosphate and then to pyruvate. When oxygen is scarce, pyruvate is converted to lactate to regenerate NAD+, allowing glycolysis to continue and ATP to be produced quickly. This setup explains why the best description is breakdown of glycogen without oxygen. It reflects rapid, short‑term energy production that doesn’t rely on the mitochondrial oxidative system. The other ideas involve substrates or conditions that require oxygen, or describe aerobic pathways, so they don’t fit anaerobic metabolism as closely.