Carb Metab

Question 1

Rate limiting step in glycolysis

Answer 1

F6P to F1,6BP by PFK1**

Question 2

First input of ATP in glycolysis

Answer 2

Glucose to G6P

Question 3

Imp hub in glycolysis

Answer 3

pyruvate

either into TCA cycle w/ oxygen present in mitochondria or converted to lactate w/o oxygen and exported from cell

Question 4

Where does gluconeogenesis occur?

Answer 4

liver

kidney

Question 5

Three key regulated steps in gluconeogenesis

Answer 5

1. Pyruvate to PEP (thru oxaloacetate, malate)
   use: Pyruvate carboxylase, PEPCK
2. F1,6BP to F6P using fructose 1,6 bisphosphatase
3. G6P to glucose (using glucose 6 phosphatase)

Question 6

Key steps in glycogen formation

Answer 6

G6P to glucose 1P, then glucose 1P to UDP-glucose

UDP glucose added to glycogen molecule using glycogen synthase (glycogen phosphorylase removes glucose from glycogen)

Question 7

Glycogen molecule

Answer 7

highly branched polymer (so need to add indiv glucose molecules but also introduce branch points)

Question 8

Pentose phosphate pathway

Answer 8

(hexose monophosphate shunt)

• when glucose is very abundant
  1. generates NADPH (fatty acid, chol biosynth, defense against oxidative stress, and white cell function)
  2. generation of 5 carbon sugars for nucleotide synthesis

Key regulated step: oxidation of G6P to 6-phosphogluconolactone by G6PD

Question 9

Regulation of flux thru a pathway

Answer 9

1. amount of substrate available
2. amount of key enzymes available
3. Allosteric regulation (can change Km or Vmax)
4. covalent modification of a key enzyme

Question 10

Counterregulatory hormones

Answer 10

glucagon
catecholamines
growth hormones
cortisol