Part A. Given what you know about the function of the glyoxylate cycle and the r
ID: 1068391 • Letter: P
Question
Part A. Given what you know about the function of the glyoxylate cycle and the regulation of the citric acid cycle, propose control mechanisms that might regulate the glyoxylate cycle. Check ALL that apply.
a. substrate-level control of succinyl-CoA synthetase
b. increasing the availability of glucose as the carbon source
c. activation of succinic dehydrogenase
d. activation of citrate lyase by acetyl-CoA or fatty acids
e. substrate-level control of citrate synthase
f. increasing fatty acids level in a cell
g. inhibition of isocitrate lyase by succinate
First i put option (b, f, g) . They said wrong. Then I put ( a, d , g). Both combinations are wrong. Could you please help me?
Explanation / Answer
substrate-level control of citrate synthase, activation of citrate lyase by acetyl-CoA or fatty acids, inhibition of isocitrate lyase by succinate (to ensure adequate flux through the citric acid cycle). (only options b, e, and g)
explanation
1. In glyoxylate cycle, isocitrate is converted to succinate and glyoxylate. Succinic dehydrogenase is required in the TCA cycle. So, its activation will not affect the glyoxylate cycle.
2. Isocitrate lyase is the key enzyme of glyoxylate cycle. So, its inhibition or activation will definitely regulate the cycle.
3. substrate-level control of succinyl-CoA synthetase- no effect on glyoxylate cycle
4. Glyoxylate cycle allows plant cells to use other sources of carbon when glucose is unavailable. So, increasing glucose availability will inhibit the cycle.
4. Yes, controlling levels of citrate synthase will regulate the cycle.
5. Increasing fatty acid levels will produce more Acetyl CoA. So, glyoxylate cycle will be enhanced.
6. Citrate lyase has no role in glyoxylate cycle.