Chapter 18: Citric Acid Cycle 1 Flashcards
pyruvate dehydrogenase complex
pyruvate + coenzyme A + NAD+ —> acetyl-CoA + NADH + CO2 + H+
What is pyruvate considered to be?
alpha keto acid
all metabolized same way:
kick off carboxyl group
attaches whats left of coenzyme A
creates acetyl-CoA and NADH that can be
used for reductions or generating energy
What does the pyruvate dehydrogenase complex structure do?
-enhances reaction rate by keeping local
-minimizes side reactions by confining intermediates
Alpha keto acid complexes all deal with these reagents…
lipoamide
thiamine pyrophosphate (B1)
coenzyme A (B5)
FAD (B2)
NAD+ (B3)
pyruvate in muscle
converted to lactate (ethanol)
Pyruvate closely related to what amino acid?
alanine
T/F Pyruvate to Acetyl-CoA is a 2 way process.
Fasle; it’s a one way process
once Co2 released into atmosphere, the process can’t be reversed
main thing that acetyl-CoA goes into
citric acid cycle
if we are well fed and don’t need energy from citric acid cycle, acetyl-CoA is converted into
lipids
minor amount drawn off to make amino acids
process of making acetyl-CoA from pyruvate
-pyruvate decarboxylated
-part is tranferred to thiamine pyruphosphate
-that transferred onto lipoamide
-transferred to coenzyme A
-acetyl-CoA is made (and dihydro-lipoamide)
What happens to the dihydrolipidamine made with acetly-CoA?
-recycled with FAD to make FADH2 and lipoamide
-FADH2 recycled with NAD+ to make NADH and FAD
primary regulators via substrate availability
pyruvate
coenzyme A
NAD+
if super low, we can’t do process
input and outputs of pyruvate dehydrogenase
input: pyruvate
output: acetyl-CoA and NADH
what process limits pyruvate dehydrogenase complex via regulation by substrate availability?
lipid catabolism
regulation by phosphorylation
PDH kinase phosphorylates pyruvate dehydrogenase complex
regulation by phosphorylation
PDH kinase phosphorylates pyruvate dehydrogenase complex
becomes inactive
reversed by PDH phosphotate
removes the phosphates and reactivates
What activates the PDH kinase?
acetyl-CoA
NADH
What inactivates kinase?
excess pyruvate
low ADP
high Ca++
what has reciprocal relationship in phoshporylation regulation?
Ca++
activates phosphotase
inactivates kinase
what effect does high blood sugar have on regulation?
-ups insulin production
-insulin uses Ca++ as second messenger
-turns up phosphotase
-turns down kinase
complex turns up and more acetyl-CoA production is converted to lipids which become stored fat
What role does muscle play in Ca++ regulation?
-adrenaline/epi released
-Ca++ stimulates muscle contraction and makes muscles work harder
