Energy production (Carbs 3) Flashcards
How does pyruvate enter stage 3 of catabolism?
not directly, is converted to acetyl coA by the enzyme pyruvate dehydrogenase
What vitamin is the PDH reaction sensitive to and why?
vitamin B, as PDH is a multienzyme complex that requires four B vitamins
What are the consequences of the PDH reaction being irreversible?
-loss of CO2 from pyruvate is irreversible
-acetyl coA can’t be converted to pyruvate and hence can’t be converted to glucose by gluconeogenesis
How can acetyl coA be made instead of from glucose?
under certain conditions acetyl coA can be made from the Beta-oxidation of fatty acids - (acetyl coA inhibits PDH allosterically)
What inhibits and activates the enzyme PDH?
-ATP and NADH inhibit
-ADP activates
PDH is activated when there is lots of glucose to be catabolised (insulin activates)
What is the TCA cycle?
a central pathway in the catabolism of sugars/fatty acids/ketone bodies/alcohol/amino acids
What type of reaction is the TCA cycle and where is it?
oxidative pathway in the mitochondria
What does the TCA cycle require?
-NAD+
-FAD
-oxaloacetate
What is the main function of the TCA cycle?
to break the C-C bond in acetate and oxidise the C- atoms to CO2
What happens to the H+ and e- removed from acetate in the TCA cycle?
transferred to NAD+ and FAD
Describe the conditions of the TCA cycle and known genetic defects
-does not function without oxygen
-no known genetic defects as would be lethal
How many molecules of ATP are generated in the TCA cycle per molecule of glucose?
32
What are the anabolic functions of the TCA cycle?
-C5 and C4 intermediates used for synthesis of non-essential amino acids
-C4 intermediates used for synthesis of haem and glucose
-C6 intermediates used for the synthesis of fatty acids
Which enzyme is important in replacing the oxaloacetate in the TCA cycle?
pyruvate carboxylase
