Say what is made, and whether carbon dioxide is released…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Say what is made, and whether carbon dioxide is released.
- Yeast in bread dough, without oxygen.
- Muscle of a runner in a sprint, when oxygen is short.
- Bacteria that turn milk into curd.
- Yeast in grape juice in a closed vat.
Need a reminder? The key ideaShow
Without oxygen, pyruvic acid takes the hydrogen of NADH, and NAD is made again. Alcoholic fermentation: pyruvic acid decarboxylase gives acetaldehyde and carbon dioxide, then alcohol dehydrogenase gives ethanol. Lactic acid fermentation: lactate dehydrogenase gives lactic acid and no carbon dioxide. The net gain is ATP for each glucose.
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) Ethanol, and carbon dioxide is released. The gas makes the dough rise.
Step 2. (b) Lactic acid, and no carbon dioxide.
Step 3. (c) Lactic acid, and no carbon dioxide.
Step 4. (d) Ethanol, and carbon dioxide is released.
Answer: (a) ethanol, CO; (b) lactic acid, none; (c) lactic acid, none; (d) ethanol, CO.
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