Calvin's team supplied algae with carbon dioxide that held radioactive carbon…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Calvin's team supplied algae with carbon dioxide that held radioactive carbon. (a) Name the algae they used and the radioactive isotope. (b) What was the first stable compound that carried the radioactive carbon? (c) How many carbon atoms does it have, and what name does this give to the pathway? (d) Check the carbon count: RuBP has carbon atoms and it takes up one carbon dioxide. How many 3-carbon molecules does it give?
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.
Step 1. The algae and the isotope. Chlorella and Scenedesmus, with carbon-14 ().
Step 2. The first stable product. 3-phosphoglyceric acid, PGA.
Step 3. The name. It has three carbon atoms, so the route is called the C3 pathway.
Step 4. The carbon count. carbon atoms, and . One RuBP and one carbon dioxide give molecules of PGA.
Answer: (a) Chlorella, Scenedesmus; carbon-14; (b) PGA; (c) carbon atoms, the C3 pathway; (d) molecules.
Discussion (0)
Log in to join the discussion.
Loading…