A young seed cell is making fatty acids for its membranes…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A young seed cell is making fatty acids for its membranes.
- Where does the cell get the acetyl CoA that it needs?
- In this cell, is the respiratory pathway working as a catabolic or as an anabolic pathway?
- Give another example of a compound that is withdrawn from the pathway to make a different compound.
- Why is the pathway called amphibolic?
Need a reminder? The key ideaShow
Carbohydrates are changed to glucose. Glycerol enters as PGAL, and fatty acids enter as acetyl CoA. Amino acids, after deamination, enter as pyruvic acid, acetyl CoA or a Krebs cycle intermediate. The pathway also supplies intermediates for building fats and proteins, so it is amphibolic.
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) From the respiratory pathway. It is made from pyruvic acid, which comes from glucose.
Step 2. (b) The pathway is working in the anabolic way for this purpose, since a compound is withdrawn to build something.
Step 3. (c) An intermediate of the Krebs cycle, such as alpha-ketoglutaric acid, is withdrawn to make an amino acid for a protein.
Step 4. (d) The pathway is used for both breaking down and building up, so it is amphibolic.
Answer: (a) from the pathway; (b) anabolic; (c) a Krebs cycle intermediate for an amino acid; (d) it works both ways.
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