M1: Carbohydrates L4

Question 1

What organ metabolizes the majority of fructose?

Answer 1

The liver.

Question 2

Write down fructose metabolism in liver.

Answer 2

see lecture 4.1 slide 33

Question 3

Write down fructose metabolism in muscle.

Answer 3

see lecture 4.1 slide 33

Question 4

Why would the cell choose to metabolize fructose one way in the liver versus the other?

Answer 4

If the liver needs to make glycerophospholipids and triacylglycerol from glycerol-3-phosphate then it will use the longer path. There is no benefit energy wise between both paths.

Question 5

If fructose is metabolized in the muscle, when does it converge with the glycolysis pathway?

Answer 5

As fructose-6-phosphate right before the PFK1 regulatory step.

Question 6

If fructose is metabolized in the liver, when does it converge with the glycolysis pathway?

Answer 6

As GAP (Glyceraldehyde-3-phosphate) right after PFK1 regulatory step.

Question 7

In terms of glucose, in the fed state, is the liver an anabolic or catabolic organ?

Answer 7

Anabolic

generates glycogen from glucose for storage

Question 8

In therms of fructose, in the fed state, how is it metabolized in the liver?

Answer 8

Fructose bypasses the PFK1 regulation to eventually be metabolized into fatty acids.

Question 9

In non-liver cells (ex: muscle) is fructose metablized in the presence of high [ATP]?

Answer 9

No. in non-liver cells, fructose does not bypass PFK in the glycolysis pathway because it gets metabolized into F6P. Therefore, in abundant [ATP], PFK is inhibited, and F6P will not be metabolized.

Question 10

Write down galactose metabolism in liver (mostly).

Answer 10

See lecture 4.1 slide 38

Question 11

What is the point of entry of galactose into glycolysis?

Answer 11

G6P (Glucose-6-phosphate) -> before PFK1

Question 12

What is galactosemia?

Answer 12

The inability to metabolize galactose due to the mutation of 3 possible enzymes in the galactose metabolism pathway.

Question 13

What 3 enzymes can be mutated if you have galactosemia and what type of galactosemia goes with the mutation?

Answer 13

1. Type 1: galactose-1-phosphate uridylyl transferase mutation
2. type 2: galactokinase mutation
3. Type 3: UDP-galactose-4-epimerase mutation

Question 14

Can a galactosemic mother produce milk?

Answer 14

yes, if she has type 1 or 2 galactosemias.

Question 15

write down the pathway for how a galactosemic mother produce milk?

Answer 15

See lecture 5.1 slide 11

Question 16

Draw the metabolism of mannose.

Answer 16

See lecture 4.1 slide 43

Question 17

At what step of glycolysis does mannose metabolite enter?

Answer 17

Fructose-6-phosphate (F6P).