Mod3

Question 1

Gluconeogenesis occurs in the ___ and ____ in animals

Answer 1

Liver and kidney

Question 2

Primary function of gluconeogenesis

Answer 2

Maintaining glucose levels in blood

Question 3

Brain uses __ g glucose per day

Answer 3

120 g

(Can also use ketone bodies when glucose is unavailable)

Question 4

Glucose can be synthesized from

Answer 4

Non-carbohydrate precursors (gluconeogenic precursors), including:

1. Lactate: becomes pyruvate and enters the pathway (reversible rxn from last mod catalyze by lactate dehydrogenase) - lactate from muscles released into blood and taken up by liver to be converted back to pyruvate
2. Amino acids: amino acids from diet or protein degaradation become intermediates
3. Glycerol: triacylglycerol break down —> glycerol taken up by the liver from the blood —> converted to dihydroxyacetone phosphate

• phosphorylated to glycerol phosphate by glycerol kinase —> glycerol phosphate oxidized to dihydroxyacetone phosphate by glycerol phosphate dehydrogenase

Question 5

Number of high transfer potential phosphoryl groups spent in synthesizing glucose from pyruvate

Answer 5

6 (4 ATP + 2 GTP)

Question 6

Overall stoichiometry of gluconeogenesis

Answer 6

2 Pyruvate + 4 ATP + 2 GTP + 2 NADH + 2H+ + 6 H2O —> glucose + 4 ADP + 2 GDP + 6 Pi + 2 NAD+

-38 kj/mol

Question 7

Fructose 1,6-bisphosphatase inhibitors and activators

Answer 7

• Inhibitors: fructose 2,6-bisphosphate and AMP
• Activator: citrate

Question 8

Pyruvate carboxylase inhibitors and activators

Answer 8

• inhibitor: ADP
• activator: Acetyl CoA

Question 9

PEP carboxykinase inhibitor

Answer 9

• inhibitor: ADP

Question 10

Liver responsibility

Answer 10

Maintaining blood sugar levels by adjusting glucose and gluconeogenesis rates

• through F-2,6-Bisphosphate

Question 11

Fructose 2,6- bisPhosphate

Answer 11

• Activates glycolysis (PFK)
• inhibits gluconeogenesis (F 1,6-bisphosphatase)
• enzymes: PFKase-2 and FBPase-2 (present in the same protein - bifunctional enzyme w two distinct domains - kinase domain and phosphatase domain (also regulatory domain))

Question 12

Insulin’s effect on gluconeogenesis

Answer 12

Inhibits gluconeogenesis

Question 13

Insulin

Answer 13

Released by pancreas after a meal to help tissues take up more glucose - inhibits gluconeogenesis (but not in type 2 diabetes - insulin resistance)

Question 14

Type 2 diabetes

Answer 14

Insulin resistance- body doesn’t respond properly to insulin - produce glucose even when it is enough, leading to hyperglycemia

• sugar increases osmolarity of blood and draws water out of tissues - excessive thirst and frequent urination
• insulin resistance associated w obesity
• drugs target inhibiting liver gluconeogenesis, increasing insulin sensitivity, stimulating ability of pancreas to release insulin

Question 15

Cori cycle

Answer 15

Lactate to glucose

• Muscle produces lactate from pyruvate after breaking down glucose during strenuous exercise and the absence of oxygen
• lactate released into blood - taken up by liver - converted back to pyruvate using lactate dehydrogenase
• pyruvate converted to glucose by gluconeogenesis
• blood glucose levels replenished, muscle can use this glucose to generate atp via glycolysis again

Question 16

Gluconeogenesis

Answer 16

The synthesis of glucose from non-carbohydrate precursors

Question 17

Obligate allosteric activator

Answer 17

An allosteric activator that is required to be beyond to an enzyme for it to have catalytic activity

Question 18

Reciprocal regulation

Answer 18

A situation where an allosteric molecule inhibits one pathway and activates the opposing pathway, such as that which occurs with glycolysis and gluconeogenesis