Multiple Choice
Why is a different enzyme involved in each step of glycolysis?
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8. Respiration
Glycolysis
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Which of the following best describes the primary function of the first half of glycolysis?
A
It produces carbon dioxide and water as end products.
B
It generates ATP and NADH by substrate-level phosphorylation.
C
It invests ATP to phosphorylate glucose and split it into two three-carbon molecules.
D
It converts pyruvate into acetyl-CoA for entry into the citric acid cycle.
Verified step by step guidance1
Understand the process of glycolysis: Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells and involves the breakdown of glucose into pyruvate. It consists of two phases: the energy investment phase (first half) and the energy payoff phase (second half).
Focus on the first half of glycolysis: The primary function of the first half is to prepare glucose for further breakdown by investing energy in the form of ATP. This phase is often referred to as the 'energy investment phase.'
Explain the phosphorylation of glucose: In the first step of glycolysis, glucose is phosphorylated by ATP to form glucose-6-phosphate. This phosphorylation is catalyzed by the enzyme hexokinase. The addition of a phosphate group makes glucose more reactive.
Describe the splitting of glucose: After further phosphorylation and rearrangement, the six-carbon molecule fructose-1,6-bisphosphate is split into two three-carbon molecules: glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). This splitting is catalyzed by the enzyme aldolase.
Summarize the primary function: The first half of glycolysis invests ATP to phosphorylate glucose and split it into two three-carbon molecules, setting the stage for the energy payoff phase where ATP and NADH are generated.
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