I have asked for help from other classmates and we are so lost. Any help would be appreciated!! :)
Q: What are the major carbon-containing products and the total molar yield of ATP when mammalian cell homogenates are incubated iwth the four fatty acids listed below under condition A and condition B? Assume all necessary enzymes and coenzymes are present.
a) CH3-(CH2)8-COO
b)cis-CH3-CH=CH-CH2-CH2-COO
c)cis-CH3-CH=CH-CH2-CH2-COO and inbibitor of epimerase enzyme
d) CH3-CH(OH)-(CH2)3-COO
Condition A - the citric acid cycle is blocked by fluorocitrate, and acetyl CoA is the final degredation product
Condition B - the citric acid cycle is operating normally.
To determine the major carbon-containing products and the total molar yield of ATP under two different conditions (Condition A and Condition B), you need to understand the metabolic pathways involved in fatty acid degradation and the role of the citric acid cycle.
Here's how you can approach solving this problem:
1. Familiarize yourself with the metabolic pathways involved in fatty acid degradation:
- In the initial step, fatty acids are activated by converting them into acyl-CoA molecules.
- The breakdown of fatty acids occurs in a series of reactions involving beta-oxidation, which generates acetyl-CoA units.
- Acetyl-CoA can then enter the citric acid cycle (also known as the tricarboxylic acid or Krebs cycle), where it is further oxidized to produce ATP.
2. Understand the roles of Condition A and Condition B:
- Condition A: The citric acid cycle is blocked by fluorocitrate, and acetyl-CoA is the final degradation product. This means that no further oxidation of acetyl-CoA occurs, limiting the ATP synthesis from the citric acid cycle.
- Condition B: The citric acid cycle operates normally, allowing complete oxidation of acetyl-CoA and maximizing ATP production.
3. Analyze each fatty acid separately under both conditions:
a) CH3-(CH2)8-COO: This is a long-chain fatty acid without any specific modifications.
- Under Condition A: The fatty acid undergoes beta-oxidation until it is converted into acetyl-CoA. However, due to the blocked citric acid cycle, no ATP will be synthesized.
- Under Condition B: The fatty acid undergoes beta-oxidation, generating multiple acetyl-CoA units which then enter the citric acid cycle. This leads to the production of ATP through oxidative phosphorylation.
b) cis-CH3-CH=CH-CH2-CH2-COO: This is a cis-unsaturated fatty acid.
- Under Condition A: Similar to the previous fatty acid, beta-oxidation will occur until acetyl-CoA is formed. However, ATP synthesis is hindered due to the blocked citric acid cycle.
- Under Condition B: The unsaturated bond needs to be processed by an enzyme called enoyl-CoA isomerase to be able to enter the beta-oxidation pathway. Once inside, the fatty acid will undergo beta-oxidation, resulting in acetyl-CoA units that produce ATP in the citric acid cycle.
c) cis-CH3-CH=CH-CH2-CH2-COO (with an inhibitor of epimerase enzyme): The presence of an inhibitor of the epimerase enzyme will affect a specific step in fatty acid degradation, resulting in different products.
- Under Condition A: Beta-oxidation will occur until the inhibitor blocks the epimerase enzyme. As a result, the formation of acetyl-CoA will stop, and no ATP will be produced from the citric acid cycle.
- Under Condition B: The inhibitor does not affect the citric acid cycle, allowing complete oxidation of acetyl-CoA and ATP synthesis.
d) CH3-CH(OH)-(CH2)3-COO: This is a hydroxy fatty acid.
- Under Condition A: The fatty acid will undergo beta-oxidation, generating acetyl-CoA. However, with the blocked citric acid cycle, no ATP will be synthesized.
- Under Condition B: Beta-oxidation converts the fatty acid into acetyl-CoA, which can be further oxidized in the citric acid cycle to produce ATP.
4. Calculate the molar yield of ATP for each condition:
- To determine the total molar yield of ATP, you need to know the number of acetyl-CoA units derived from the fatty acid degradation and the amount of ATP produced from each acetyl-CoA unit in the citric acid cycle.
It is important to note that specific values for the molar yield of ATP cannot be determined without additional information, such as the precise number of acetyl-CoA units produced from each fatty acid and the ATP yield during oxidative phosphorylation. You may need to refer to literature sources or consult your instructor for additional information.
Remember, understanding the metabolic pathways and the effects of specific conditions on those pathways is crucial for determining the major carbon-containing products and the total molar yield of ATP.