L25-Metabolism Of Ketone Bodies Flashcards
What are ketone bodies
And what are the compounds
Considered alternative fuel for body
Acetoacetate
B-hydroxybutyrate
Acetone
When does ketogenesis occur
When level of acetyl coA from B oxidation inc in excess of that required for entry in to CAC
Undergoes ketogenesis in mitochondria of liver
Normal concentration of ketone bodies in blood
3mg/dl
Why are ketone bodies important sources of energy for peripheral tissue
1)soluble in aqueous solution so dont need to be incorporated in to lipoproteins or carried by albumin as do the other lipids
2)produced in liver during periods when amount of acetyl coA present exceeds that required by CAC
3)used in proportion to their concentration in blood by extrahepatic tissues such as skeletal and cardiac ms,intestinal mucosa and renal cortex
Even brain can use ketone bodies
4)Spare glucose which is important during long periods of fasting
Rate limiting step in synthesis of ketone bodies and what does the enzyme do
3 hydroxy 3 methylgutaryl(HMG) coA synthase
Combines a third mol of acetyl co A with acetoactyl coA to produce HMG coA
Present in liver only
Describe the pathway for ketone body synthesis
▪️2 acetyl coA mol and fatty acyl coA combine by thiolase to form acetoacetyl coA
▪️HMG coA synthase combines a third coA to acetoacteyl coA forming HMG CoA
▪️HMG coA lyase removed acetyl coA from HMG coA forming acetoactetate
Which can break down and form acetone and 3 hydroxybutyrate
How can acetoacetate form 3 hydroxybutyrate and acetone
Acetone: by spontaneous decarboxylation
3HB:by 3HB dehydrogenase
How can ketone body synthesis be regulated
HMG coA synthase is the regulatory enzyme: 1-activity inc fatty acids in blood 2-glucagon hr activates HMG-coA 3-insulin inhibits HMG coA 4-inhibited by high levels of coASH
How does the process of ketolysis occur and what is it
Utilization of ketone bodies
Acetoacetate is reactivated by converting back to acetoactyl coA
Done by mitch enzyme thiophorase in non hepatic tissues and uses succinyl coA as main source of coenzyme A
What is ketosis
When rate of formation is greater than their rate of use
In blood(ketonemia)
In urine(ketonuria) +acetone odor in breath
Not severe
What are the causes of ketosis
1-starvation with depletion of carb stores
2-diabetic person with uncontrolled blood glucose
3-following ketogenic diet
What is ketoacidosis
When acetoacetic acid and b hydroxybuytric acid increase
Buffered by alkali reserce(HC03)
Depletion of alkali reserve
Severe
Common with uncontrolled diabetes known as diabetic ketoacidosis which can lead to coma and death
