Glycolysis and Gluconeogenisis

Question 1

Glycolysis reaction

Answer 1

Glucose + 2NAD+ + 2ADP + 2Pi —> 2Pyruvate + 2NADH + 2 net ATP (use 2 in the process)

Question 2

Glycolysis steps

Answer 2

Glucose -> Glucose 6 P (using hexokinase to trap glc in cell) USING ATP and Mg

G6P-> Fructose 6P (phosphoglucose isomerase)

F6P -> Fructose 1,6 bisphosphate (using phosphofructose kinase 1 the commited step , highly regulated) USING ATP and Mg

Fructose 1,6 bisphosphate–> Dihydroxyacetone phosphate schiff base + Glyceraldehyde 3 phosphate (using Aldolase B (liver) A(muscle)) DHAP and GAP are interchanged via triose phosphate isomerase only GAP continues on to glycolysis

2x

Glyceraldehyde 3 Phosphate-> 1,3 bisphosphoglycerate (using glyceraldyhyde 3 phosphate dehydrogenase and NAD+ -> NADH)

1,3 bisphosphoglycerate-> ATP + 3 phosphoglycerate (using phosphoglycerate kinase)

3 phosphoglycerate-> 2 phosphoglycerate (using phosphoglycerate mutase)

2 phosphoglycerate-> Phosphoenolpyruvate (PEP) using enolate

PEP -> pyruvate + ATP (pyruvate kinase)

Question 3

Irreversible reactions in glycolysis

Answer 3

irreversible reactions in glycolysis are typically comitted and highly regulated

hexokinase/glucokinase
PFK1 (rate limiting step of glycolysis)

pyruvate kinase

Question 4

Hexokinase vs Glucokinase

Answer 4

hexokinase: in most tissues except liver and B cells, low Km, low Vmax, not induced by insulin, inhibited by G6P
glucokinase: in liver and B cells, high Km, high Vmax, insulin induced, not inhibited by G6P

Question 5

Gluconeogenisis

Answer 5

Pyruvate-> oxaloacetate (by Pyruvate carboxylase)

oxaloacetate-> PEP (by PEP carboxykinase)

PEP-> 2 phosphoglycerate->->Fructose 1,6 Bisphosphate

fructose 1,6 bisphosphate-> fructose 6 phosphate (fructose 1,6 bisphosphatase)

fructose 6 phosphate-> glucose 6 p

glucose 6 P-> glucose (glucose 6 phosphatase)

Pathway Produces Fresh Glucose

Question 6

Pyruvate carboxylase

Answer 6

converts pyruvate to oxaloacetate (reversed via PEPCK)
needs biotin and ATP, done thru the mito, pepck in cyto, activated by acetyl coA

Mito malate dehydrogenase converts oxaloacetate to malate so that it can leave mito (it uses NADH-> NAD with NAD going to cyto)

Aspartate amino transferase (AAT) converts oxaloactetate to aspartate so that it can leave mito

Malate and aspartate translocate via transporter

Then once in cyto malate dehydrogenase get converted back to oxaloacetate and aspartate is converted by cyto AAT (using NAD)

Cytosolic oxaloacetate is converted to PEP via PEP CK and GTP

Question 7

PEPCK (Phosphoenolcarboxykinase)

Answer 7

converts oxaloacetate to PEP using GTP and then pushed thru the reverse glycolysis until fructose 1 6 bisphosphatase

Question 8

Fructose 1 6 bisphosphatase

Answer 8

converts fructose 1 6 bisphosphate to fructose 6 phosphate

RATE limiting step of gluconeogenisis

inhibited by AMP and fructose 2 6 bisphosphatase

activated by citrate

Question 9

Glucose 6 phosphatase

Answer 9

converts glucose 6 phosphate to glucose

in luminal side of ER, expressed in liver