LECTURE 2 - GLYCOLYSIS

Question 1

why does phosphorylated glucose stay trapped in the cell?

Answer 1

phosphorylated compounds do not transport easily
too big, cannot fit through GLUT2

Question 2

how do hexokinase and glucokinase compare to each other in these categories:
1.catalysed reaction
2.substrate specificity
3.tissue of prevalence
4.affinity constant (Km in mM)
5. modulator
6. metabolic consequence

Answer 2

Question 3

how is glucokinase regulated?

Answer 3

by glucokinase regulatory protein (GKRP)
binding partner that traps GK in the nucleus when glucose levels are too low
when glucose levels are high GKRP releases glucokinase to the cytoplasm where it can produce G6P
GK activates when HK is overwhelmed

Question 4

what reaction does phosphoglucose isomerase catalyse (PGI)?

Answer 4

G6P –> <– fructose -6 phosphate
(equilibrium arrows)

Question 5

what drives the PGI reaction?

Answer 5

at equilibrium, so driven by abundance of substrates
can easily go both ways
not a regulatory step of glycolysis

Question 6

what is the reaction that phosphofructokinase 1 catalyses (PFK1)?

Answer 6

fructose 6 phosphate + ATP –> (Mg2+ above the arrow) fructose-1-6-bisphosphate + ADP

Question 7

what is special about the PFK1 reaction?

Answer 7

highly exergonic
irreversible
THE step that commits the cell to metabolise glucose
specific to glycolysis

Question 8

what are activators and inhibitors of PFK1?

Answer 8

activators: AMP, F2,6P
inhibitors: ATP, citrate

Question 9

what are the two states of PFK1?

Answer 9

Question 10

which is more potent at its function: AMP or ATP?

Answer 10

AMP is more potent activator, overcomes the ATP inhibition

Question 11

what does adenylate kinase do and the biochemical consequence?

Answer 11

adenylate kinase regenerates ATP from two molecules of ADP
2 ADP-> <- ATP+AMP
adenylate kinase not only keeps ATP abundant for exercise but also generates AMP which activates PFK1 and therefore glycolysis