(a) How many turns of the Calvin cycle make one glucose? …
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
(a) How many turns of the Calvin cycle make one glucose? (b) How many ATP and how many NADPH does one glucose cost? (c) How many ATP does a leaf spend to make glucose molecules?
Need a reminder? The key ideaShow
Calvin cycle (C3 pathway, in the stroma): carboxylation (RuBP, 5C, plus carbon dioxide, by RuBisCO, gives two 3-PGA, 3C), reduction (2 ATP and 2 NADPH for each carbon dioxide, gives triose phosphate), regeneration (1 ATP for each carbon dioxide). Each carbon dioxide: 3 ATP and 2 NADPH. One glucose: 6 turns, 18 ATP, 12 NADPH. Six turns: 6 RuBP (30 C) and 6 CO2 (6 C) give 12 triose phosphate (36 C); 2 leave as glucose (6 C) and 10 (30 C) rebuild 6 RuBP.
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.
Given. Each turn fixes one carbon dioxide and spends ATP and NADPH.
Step 1. Turns. Glucose has carbon atoms, so it takes turns.
Step 2. ATP. ATP.
Step 3. NADPH. NADPH.
Step 4. Five glucose. ATP.
Check. The ATP is times the NADPH, as it must be: against for each turn.
Answer: (a) turns; (b) ATP and NADPH; (c) ATP.
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