A balance sheet of ATP for one glucose rests on some assumptions…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A balance sheet of ATP for one glucose rests on some assumptions. Say whether each statement below is one of them, or is a fact about a living cell that the count ignores.
- Glycolysis, the Krebs cycle and the electron transport system follow one after another.
- The cell withdraws intermediates from the pathway to build other compounds.
- Only glucose is respired.
- ATP is used as soon as it is made.
Need a reminder? The key ideaShow
One NADH gives ATP and one FADH gives ATP. For one glucose there are ATP made directly, NADH (2 from glycolysis, 2 from the link reaction, 6 from the Krebs cycle) and FADH. NCERT counts the NADH of glycolysis as ATP each and states a net gain of ATP. The count is theoretical.
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) An assumption. The count takes the stages in order.
Step 2. (b) A fact the count ignores. The count assumes that no intermediate is used for anything else.
Step 3. (c) An assumption. No other substrate is supposed to enter.
Step 4. (d) A fact the count ignores. A living cell spends ATP as it is made.
Answer: (a) assumption; (b) fact ignored; (c) assumption; (d) fact ignored.
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