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Multiple Choice
In glycolysis, what is the initial substrate (starting molecule) that enters the pathway in most cells?
A
Pyruvate
B
Acetyl-CoA
C
Glycogen
D
Glucose
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Verified step by step guidance
1
Understand that glycolysis is the metabolic pathway that breaks down a six-carbon sugar molecule to produce energy in the form of ATP.
Identify the molecule that enters glycolysis at the very beginning; this molecule must be a six-carbon sugar since glycolysis involves splitting it into two three-carbon molecules.
Recall that pyruvate is actually the end product of glycolysis, not the starting molecule.
Recognize that Acetyl-CoA is a molecule that enters the citric acid cycle after glycolysis, so it is not the initial substrate for glycolysis.
Note that glycogen is a storage form of glucose and must be broken down into glucose before entering glycolysis, so the direct initial substrate is glucose itself.