Metabolism Flashcards
Name the 3 non carbohydrate precursors of glucose :
1 lactate
2 amino acids (alanine in skeletal muscle)
3 glycerol (triacylglycerols in fat tissue )
Which organs are involved in gluconeogenesis :
Liver (90%), kidney and small intestine
Where in the cells does gluconeogenesis occur?
Cytosol (except for the first reaction )
Most of the same glycolysis enzymes involved
Summarise how gluconeogenesis occurs:
Reversal of glycolysis except for 3 steps
- Pyruvate converted to PEP
- F1,6BP converted to F6P
- G6P converted to glucose
Explain the importance of pyruvate carboxylate
Catalyses an important anapleurotic reaction
This means it maintains the conc of Krebs cycle intermediates, allowing it to be a continuous process
Name the reactions involved in gluconeogenesis and the enzymes involved
How do the 3 glucose precursors join the gluconeogenesis pathway ?
Lactate —> pyruvate
Lactate DH
Amino acids —> oxaloacetate + pyruvate
Transamination
Glycerol —>dihydroxyacetone phosphate —>glyceraldehyde 3-phosphate
State the 2 condition for gluconeogenesis
Low [glucose] and high [ATP]
glycolysis and gluconeogenesis can occur simultaneously
true or false
False
when one pathway is active, the other must be inactive
What conditions inhibit Gluconeogenesis
High AMP/F1,6P/ADP
What conditions stimulate gluconeogenesis
High acetyl CoA / citrate
What conditions inhibit glycolysis
High ATP/Citrate/H+/alanine
What conditions stimulate glycolysis
High F2,6P as this stimulate PFK-1 involved in the irreversible step; high AMP (as this indicate there is low ATP); insulin secretion
Describe the effects of insulin
Promote synthesis of glycolysis enzymes e.g. PFK/PK/PFK2
Inhibit synthesis of PEPCK ; this inhibits gluconeogenesis
Describe the effects of glucagon
Increases expression of PEPCK/F1,6BPase
increased gluconeogenesis
Draw the Krebs cycle
citrate is krebs special substrate for making oxaloacetate.
What is the PDH reaction
the link reaction
converts pyruvate to acetyl CoA
Name the4 5 coenzymes of PDH
Thiamine pyrophosphate (TPP)
Lipoamide
CoA
FAD+
NAD+
draw the mechanism of the PDH reaction
Name the 3 enzymes found within the PDH complex
E1 pyruvate decarboxylase
E2 hydrolipoyl transacetylase
E3 dihydrolipoyl dehydrogenase
What conditions cause activation of PDH
Increased [insulin] and [Ca2+]
this cause dephosphorylation of PDH
What conditions cause the inhibition of PDH
Increased ATP/NADH/Acetyl CoA
results in phosphorylation of PDH via kinase
Name the 3 enzymes needed for glycogen formation
Glycogenin
glycogen synthase
branching enzyme
State the role of glycogenin
Combine UDP-glucose (activated form of glucose) to tyrosine