Glycolysis

Question 1

Hexokinase:
Transfer of phosphoryl group to _____
Transfer of phosphoryl group facilitated by ____

Answer 1

C6 OH of glucose
Electrostatic catalysis
Invest 1 ATP

Question 2

Phosphoglucose Isomerase

Answer 2

Isomerized between aldose and ketose

Glucose –> Fructose

Question 3

Phosphofructokinase

Answer 3

Consumes 2nd ATP
Attach to C1 of fructose
Slowest reaction

Question 4

Aldolase
What forms Schiff base? What is base catalyst?
Schiff base facilitates split.

Answer 4

Lys: forms Schiff base by Nuc attack
Asp: base catalyst (ABC)
C3/C4 split- aldehyde and ketone
Despite high positive delta G, in vivo products are substrates for the next

Question 5

Triose phosphate isomerase: what does it mean to be catalytically perfect?

Answer 5

catalytically perfect, limited by rate of diffusion
Low barrier H bonds
Active site protein loop stabilizes transition state
pulls aldolase forward

Question 6

G3P dehydrogenase

Answer 6

Oxidation/Phosphorylation
Aldehyde: oxidize, NAD+ reduced
Pi added to aldehyde

Covalent catalysis by CYS RESIDUE
Pulls aldolase forward
Attack by phosphate

SH of active site Cys forms covalent bond to G3P
Thioester bond

Question 7

Phosphoglycerate kinase

Answer 7

Drive ATP formation
removal of phosphate from acyl phosphate: largeree energy
pairing = net decrease free energy

Question 8

Phosphoglycerate mutase

Answer 8

His residue in active site- transfer of phosphoryl groups
C3 –> C2
Reversible

Question 9

Enolase

What facilitates exit?

Answer 9

Dehydration (water released)
Mg2+ Ion coordination with C3 OH to make better leaving group

Inhibited when fluoride and Pi from complex with Mg2+ ion

Question 10

Pyruvate Kinase

Answer 10

1) ADP attacks phosphoryl group of phosphoenolpyruvate to make ATP and enolpyruvate
2) Tautomerization (isomerization by shift of H atom) of enolpyruvate to pyruvate

Question 11

Where does gluconeogensis occur?

Answer 11

Liver and Kidneys

Question 12

Pyruvate Carboxylase

Answer 12

ATP/CO2 consumed

Makes 4C Oxaloacetate

Question 13

Phosphoenolpyruvate Carboxykinase

Answer 13

GTP consumed, CO2 created

Question 14

During gluconeogensis, Phosphoglycerate kinase reaction consumes ATP and NADH is used to reverse ______

Answer 14

G3P dehydrogenase

Question 15

_______ are gluconeogenic precursors

Answer 15

Amino acids

Question 16

Regulation step of gluconeogenesis

Answer 16

Fructose biphosphatase

Hydrolysis of phosphoryl group from C1

Question 17

G6P – >glucose

Answer 17

glucose 6 phosphatase

Hydrolyzes phosphoryl group on C6

Question 18

High levels of F-2,6- bip

Answer 18

Glycolysis

Question 19

Why are amino acids (except leucine/lysine) main gluconeogenic precursors?

Answer 19

They can all be converted to oxaloacetate.

During starvation, proteins broken down and used to produce glucose to fuel CNS
Fatty acids can’t be converted to oxaloacetate
3C glycerol backbone of triacylglycerols is precursor

Question 20

Why would cells with no gluconeogenesis have fructose biphosphatase anyway?

Answer 20

When fructose bisphosphate and phosphofructokinase are both active, net result in hydrolysis of ATP.