Glycolysis, PPP, TCA, B-Oxidation

Question 1

Hexokinase/Glucokinase

Answer 1

Traps glucose in the cell by phosphorylating it to glucose-6-phosphate.
Hexokinase - present in most tissues and has a low Km. Inhibited by glucose-6-phosphate
Glucokinase - present in beta cells and hepatocytes and has high Km. Activated by insulin. High Km allows for uptake proportional to that of blood glucose levels. (only want to transport excess)

Question 2

PFK(I)

Answer 2

Converts fructose-6-phospate to 1,3 bisphosphofructose which is used for further glycolysis. Inhibited by ATP and citrate, activated by AMP.

Question 3

PFK(II)

Answer 3

Converts fructose-6-phosphate into 2,6 bisphosphofructose which activates PFK(I). PFK(II) is activated by insulin and inhibited by glucagon.
Found mostly in the liver (continues gycolysis even at high ATP concentrations to generate glycogen, fatty acids, etc)

Question 4

Glyceraldehyde-3-phosphate Dehydrogenase

Answer 4

Converts glyceraldehyde-3-phosphate to 1,3 bisphosphoglycerate. Oxidation reaction that is coupled to the reduction of NAD+ to NADH.

Question 5

3-phosphoglycerate kinase

Answer 5

Converts 1,3-phosphoglycerate to 3-phosphoglycerate. Generates ATP from ADP

Question 6

Pyruvate kinase

Answer 6

Converts phosphoenolpyruvate(PEP) to Pyruvate. Generates ATP from ADP.

Question 7

Pyruvate dehydrogenase

Answer 7

Converts pyruvate into Acetyl-CoA. Reduces NAD+ to NADH. Excess Acetyl CoA inhibits pyruvate dehydrogenase.

Question 8

Glycogen synthase

Answer 8

Forms alpha-1,4 glycosidic bond (linear bond). Inhibited by glucagon and epinephrine

Question 9

Blanching enzyme AKA alpha-1,4:alpha-1,6 transferase)

Answer 9

Forms alpha-1,6 glycosidic bond (branched bond) by breaking a 1,4 bond and reorganizing into a 1,6 branch

Question 10

Glycogen phosphorylase

Answer 10

Breaks alpha-1,4 bonds

Question 11

Debranching enzyme AKA alpha-1,4:alpha1,6 glucosidase)

Answer 11

Breaks alpha-1,6 bonds and converts to 1,4 bonds

Question 12

Substrates for gluconeogenesis

Answer 12

glycerol-3-phosphate (from fats)
lactate (from anaerobic glycolysis)
gluconeogenic amino acids (all except leucine and lysine)

Question 13

Pyruvate carboxylase

Answer 13

Mitochondrial enzyme that is activated by acetyl-CoA. Converts acetyl-CoA into oxaloacetate

Question 14

Phosphoenolpyruvate carboxykinase (PEPCK)

Answer 14

Induced by glucagon and cortisol. Converts oxaloacetate to phosphoenolpyruvate (PEP). Uses GTP.

Question 15

Fructose-1-6-bisphosphatase

Answer 15

Converts 1,6-bisphosphofructose to fructose-6-phosphate. Activated by ATP.

Question 16

Glucose-6-phosphatase

Answer 16

Found in the lumen of the ER of hepatocytes. Converts glucose-6-phosphate to glucose.

Question 17

Glucose-6-Phosphate dehydrogenase

Answer 17

Converts glucose-6-phosphate to 6-phosphogluconate. 1st step in the PPP is also the RATE LIMITING.

Question 18

Glycolysis Products

Answer 18

2 ATP, 2 NADH, 2 pyruvate, 2 H2O

Question 19

PPP Products

Answer 19

2 NADPH, Ribose-5-phosphate for nucleotide synthesis.

Question 20

3 points of TCA regulation

Answer 20

• Citrate Synthase
  Inhibited: ATP, NADH, succinyl-CoA, citrate
  Activated: NONE
• Isocitrate Dehydrogenase
  Inhibited: ATP, NADH
  Activated: ADP, NAD+
• a-Ketoglutarate dehydrogenase
  Inhibited: ATP, NADH, succinyl-CoA
  Activated: ADP, Ca2+