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Glycolysis spends ATP before it makes any…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Glycolysis spends ATP before it makes any.
- Why does the cell spend ATP at the start?
- A poison blocks only the last step of glycolysis, PEP to pyruvic acid. The pathway still runs as far as PEP. What is the net gain of ATP for each glucose now?
- What compound piles up?
- What is the net gain of NADH now?
Need a reminder? The key ideaShow
Glycolysis, in the cytoplasm, turns one glucose into two pyruvic acid. ATP is used at two steps and made at two steps that run twice. The net gain is ATP and NADH for each glucose. NADH is formed only where PGAL becomes BPGA. Invertase splits sucrose into glucose and fructose.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The two phosphate groups make the sugar ready to split, and they put it on a path from which it cannot leave. This is like spending money to earn more.
Step 2. (b) ATP used: . ATP made before the blocked step: BPGA to PGA, twice, so . Net: ATP.
Step 3. (c) Phosphoenolpyruvate (PEP) piles up.
Step 4. (d) NADH is formed before the blocked step, so the gain is still NADH.
Answer: (a) to prepare the sugar to split; (b) ATP; (c) PEP; (d) NADH.
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