Carbohydrate Metabolism I

Question 1

Glucokinase vs Hexokinase

Answer 1

Question 2

Phosphofructokinase-1 (PFK-1)-catalysis

Answer 2

Question 3

Pyruvate Kinase Catalysis

Answer 3

Question 4

Production of F-2,6-BP

Answer 4

Question 5

PFK1 is inhibited by ____ and activated by ____.

Answer 5

PFK1 is inhibited by ATP and activated by AMP.

Question 6

How the liver bypasses typical ATP-mediated glycolysis inhibition

Answer 6

Insulin signaling generates F-2,6-BP. F-2,6-BP activates PFK-1 desite high ATP.

This generates F-1,6-BP. F-1,6-BP activates Pyruvate Kinase despite high ATP.

However, if glucagon is also present, the glucagon receptor -> cAMP -> PKA mediated phosphorylation of pyruvate kinase will deactivate this step, preventing liver fatty acid synthesis.

Question 7

Phosphofructokinse-2 (PFK-2) regulation in the liver

Answer 7

Question 8

Glycolysis net equation

Answer 8

Question 9

Skeletal muscle glucose

Answer 9

Question 10

Glycolysis vs Gluconeogenesis

Answer 10

Question 11

2,3-bisphosphoglycerate generation in erythrocytes

Answer 11

Question 12

How does the pancreas sense glucose levels?

Answer 12

Increased ATP blocks the K⁺ channel.

Question 13

fructose-2,6-bisphosphate

Answer 13

Allosteric regulator of PFK1 in the liver. Increases in response to insulin signaling and serves as a second messenger.

Stimulates glycolysis even in the presence of high ATP levels. This is important as it allows the liver to bypass typical PFK-1 regulation in order to generate the Acetyl-CoA it needs to make fat.

Question 14

Glucose levels in the fed state are ___ and drop to ___ in the fasted state.

Answer 14

Glucose levels in the fed state are 8 mM and drop to 4 mM in the fasted state.

Question 15

The Cori Cycle

Answer 15

Question 16

Three fates of glucose

Answer 16

1. Storage as glycogen
2. Pentose Phosphate Pathway
3. Glycolysis

Question 17

Phases of glycolysis

Answer 17

Question 18

Type ___ skeletal muscle is always glucose dependent.

Answer 18

Type IIb skeletal muscle is always glucose dependent.

Therefore there is a high baseline Glut4 expression which is not substantially upregulated during fasting or exercise.

Question 19

The red blood cell uses glucose transporter ____.

Answer 19

The red blood cell uses glucose transporter Glut1.

Km ~ 1 mM

Question 20

Glycolysis outline

Answer 20

Question 21

Once fructose-6 phosphate is phosphorylated, it is committed to ____ rather than ____.

Answer 21

Once fructose-6 phosphate is phosphorylated, it is committed to glycolysis rather than glycogen formation or the pentose phosphate pathway

Question 22

The renal medulla is _____ and thus performs glycolysis due to ____.

Answer 22

the renal medulla is oxygen-limited and thus performs glycolysis due to lack of adequate oxygen.

Question 23

Which pathway glucose proceeds down depends on the _____ of each pathway.

Answer 23

Which pathway glucose proceeds down depends on the activity of the rate determining step of each pathway.

Question 24

In cells that lack mitochondria, or in muscle that is exercising anaerobically, ____ must be regenerated somehow to allow glycolysis to continue.

Answer 24

In cells that lack mitochondria, or in muscle that is exercising anaerobically, NAD⁺ must be regenerated somehow to allow glycolysis to continue.

In this case, the electrons are transferred from NADH to pyruvate itself, producing lactate and regenerating NAD.

Question 25

In the ____, ____, and the____, glucose is a preferred fuel and is used constantly.

Answer 25

s. In the brain, renal medulla, and the red blood cell, glucose is a preferred fuel and is used constantly.

Question 26

All pathways of glucose metabolism require the same initial step, ___

Answer 26

All pathways of glucose metabolism require the same initial step, phosphorylation of glucose by glucokinase or hexokinase

Question 27

Fates of pyruvate

Answer 27

Question 28

Role of glucose in various tissues

Answer 28

Question 29

Type ___ muscle can perform beta-oxidation of fatty acids as a fuel source.

Answer 29

Type I muscle can perform beta-oxidation of fatty acids as a fuel source.

Question 30

Citric acid cycle from 10,000 ft

Answer 30