Ketogenesis Flashcards
When will Ketone Body Synthesis typically occur?
When Glycogenolysis & Gluconeogenesis substrates are exhausted (starvation)
Once Acetyl CoA is produced through Fatty Acid Oxidation, what two pathway’s can it be utilized for?
Ketone Bodies or TCA Cycle
What is the first step of Ketone Body Synthesis?
x2 Acetyl CoA’s combine to form Acetylacetyl CoA
What is the enzyme that catalyzes the reaction of combining x2 Acetyl CoA’s to form Acetylacetyl CoA?
Thiolase
What is the 2nd step of Ketone Body Synthesis?
Acetylacetyl CoA converts to HMG-CoA
What is the enzyme that converts Acetylacetyl CoA into HMG-CoA?
HMG-CoA Synthase
What is unique about the 2nd step of Ketone Body Synthesis?
A 3rd Acetyl CoA Molecule is added to Acetylacetyl CoA to make HMG-CoA
What is the 3rd step of Ketone Body Synthesis?
HMG-CoA is converted into Acetoacetate
What is the enzyme that converts HMG-CoA into Acetoacetate?
HMG-CoA Lyase
What is unique about step 3 of Ketone Body Synthesis?
An Acetyl CoA molecule is produced as a byproduct (essentially recycling the molecule)
What is the first ketone that is produced in ketone body synthesis?
Acetoacetate
Once the first ketone is formed in ketone body synthesis, how many pathway options are available for further conversions?
2 pathway options
What is step 4(A) of Ketone Body Synthesis?
Acetoacetate is converted into Acetone
What is the enzyme that converts Acetoacetate into Acetone?
Acetoacetate Decarboxlyase
What is a byproduct of step 4A of Ketone Body Synthesis?
CO2
What is step 4(B) of Ketone Body Synthesis?
Acetoacetate is converted into Beta-Hydroxybutyrate
What is the enzyme that converts Acetoacetate to Beta-Hydroxybutyrate?
Beta-Hydroxybutyrate Dehydrogenase
What are 3 ketones produced from Ketone Body Synthesis?
Acetoacetate, Acetone & Beta-Hydroxybutyrate
In Starvation states, why can’t the TCA Cycle produce fuel?
Oxaloacetate is depleted from reoccurring cycles of gluconeogenesis
What identical pathophysiology occurs in starvation states but is a diabetic condition?
Diabetic Ketoacidosis
In Diabetic Ketoacidosis, if Hyperglycemia is high what is the status of Insulin & Glucagon?
Low Insulin (Type 1 Diabetic)
High Glucagon (b/c of low Insulin)
If insulin is low, what metabolic pathway cannot function?
Glycolysis
If Glucagon is high, what metabolic pathway is running?
Gluconeogenesis
How is Alcohol (Ethanol) Metabolized?
Ethanol > Acetaldehyde > Acetate
What are the byproducts of converting Ethanol to Acetaldehyde?
NAD+ / NADH
In chronic alcohol consumption (increased ethanol) what effect to alcohol metabolism byproducts is observed?
Decreased NAD+
Increased NADH
Why is decreased NAD+ & Increased NADH an issue for oxidative metabolism?
To form oxaloacetate (for use in the TCA cycle) NAD+ is needed to convert to NADH to form oxaloacetate.
No NAD+ , No Oxaloacetate , No Gluconeogenisis (or) TCA Cycle
What is a good way to remember how/why ketones are produced in alcoholism?
“NAD+-y Light”
What is the rate-limiting enzyme of Ketone Body Synthesis?
HMG-CoA Synthase
