Advanced Biology: Cell Respiration, Krebs Cycle and Genetics
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1. Glycolysis and the Krebs Cycle
Cellular respiration begins with glycolysis in the cytoplasm. Glucose is converted into pyruvate, producing a small amount of ATP and NADH. Pyruvate then enters mitochondria and contributes to the Krebs cycle.
The Krebs cycle does not directly produce large amounts of ATP. Its main role is creating electron carriers such as NADH and FADH2, which deliver electrons to the next stage.
Worked example
One glucose molecule enters glycolysis and produces 2 pyruvate molecules. These molecules enter mitochondria, where the Krebs cycle produces NADH and FADH2. These carriers later provide electrons for ATP production.
1.Glycolysis occurs in the cytoplasm.
2.The Krebs cycle produces most cellular ATP directly.
3.NADH transports high-energy electrons.
Exam strategy
Focus on understanding underlying concepts — exam questions test application, not memorization.
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