6 Questions
Which condition will result in a high rate of de novo synthesis of fatty acids?
A high-carbohydrate diet in a well-fed state
What effect does insulin have on the rate of de novo synthesis of fatty acids?
Activates pyruvate dehydrogenase complex
Which molecules inhibit the activity of acetyl-CoA carboxylase?
Glucagon and epinephrine
Through which pathway(s) is NADPH produced for de novo fatty acid synthesis?
Pentose phosphate pathway and malate pyruvate cycle
What impact do fatty acids have on citrate regarding de novo synthesis of fatty acids?
Inhibit the exit of citrate from the mitochondria into the cytosol
Which statement correctly describes the role of citrate in de novo synthesis of fatty acids?
Citrate activates acetyl-CoA carboxylase
Study Notes
Regulation of De Novo Synthesis of Fatty Acids
Nutritional State
- De novo synthesis rate is high in well-fed individuals with a high-carbohydrate diet, converting surplus glucose to fat.
- Restricted caloric intake depresses de novo synthesis rate.
Enzymes Involved in De Novo Synthesis
- Acetyl-CoA carboxylase is the rate-limiting enzyme in de novo synthesis.
- Increase in acetyl-CoA carboxylase activity is caused by:
- Citrate
- Insulin, which also stimulates de novo synthesis by:
- Increasing glucose transport into the cell for fatty acid synthesis
- Activating pyruvate dehydrogenase complex to convert pyruvate into acetyl-CoA
- Inhibiting lipolysis in adipose tissue
- Inactivation of acetyl-CoA carboxylase is caused by:
- Hormones such as glucagon and epinephrine
- Fatty acids, which exhibit negative feedback inhibition and also:
- Inhibit citrate exit from the mitochondria into the cytosol
- Inhibit pyruvate dehydrogenase complex, reducing available acetyl-CoA for de novo synthesis
Sources of NADPH
- NADPH for fatty acid synthesis comes from:
- Pentose phosphate pathway in the cytoplasm
- Malate pyruvate cycle, where NADPH is formed in the cytoplasm during malate to pyruvate conversion
This quiz covers the regulation of de novo fatty acid synthesis, including the effects of nutritional state and enzymes involved in the process.
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