Carbohydrate Metabolism II

Question 1

PEP Carboxykinase

Answer 1

Question 2

Sources of Gluconeogenesis Precursors

Answer 2

Question 3

Glycogen branching cartoon

Answer 3

Question 4

In exercising muscle, ____ also helps to activate phosphorylase kinase.

Answer 4

In exercising muscle, the elevated calcium (released to promote contraction) also helps to activate phosphorylase kinase.

Question 5

Hepatomegaly usually indicates. . .

Answer 5

. . .defects in liver carbohydrate metabolism.

Question 6

Regulation of glycogen phosphorylase

Answer 6

Question 7

NAD⁺ and NADP⁺

Answer 7

Question 8

Ketogenic-only amino acids

Answer 8

Leucine and Lysine. Thus they cannot be used to generate glucose.

Question 9

Key Gluconeogenesis Steps

Answer 9

Question 10

Why is glycogen stored as a polymer?

Answer 10

The high concentration of glucose 6-phosphate would create a strong osmotic load on the cell, causing water to enter and swell the cell, causing it to lyse

Question 11

Glycogen phosphorylase

Answer 11

Question 12

Glycogen molecular structure

Answer 12

Question 13

Glycogen branching enzyme creates ____ linkages.

Answer 13

Glycogen branching enzyme creates α1→6 linkages.

Question 14

Glutathione Production

Answer 14

Question 15

Ratios of NAD⁺ to NADH and NADP⁺ to NADPH.

Answer 15

Question 16

Akt in glycogen synthesis

Answer 16

Akt will also help stimulate glucose transport (Glut4)

Question 17

Role of α1→6 glucosidases in glycogenolysis

Answer 17

α1→6 glucosidases remove the terminal α1→6 -bound glucose in a glycogen branch, leaving a linear chain.

Question 18

Glycogenolysis and gluconeogenesis have the same _____.

Answer 18

Glycogenolysis and gluconeogenesis have the same terminal step.

This step is dephosphorylation by glucose-6-phosphatase, which produces free glucose that may be exported into the bloodstream.

Question 19

UDP glucose synthesis

Answer 19

Question 20

Glycogen synthase regulation

Answer 20

Akt is what phosphorylates GSK3, turning it off.

Question 21

In order for glycogen synthase to add a glucose, the existing glycogen molecule must be ____.

Answer 21

In order for glycogen synthase to add a glucose, the existing glycogen molecule must be at least 4 glucose units long.

Question 22

Thus the only storage forms of glucose in the body are. . .

Answer 22

1. Glycogen, which is used quickly
2. Amino acids, stored in muscle, which must be converted into glucose via gluconeogenesis
3. Glycerol, which is stored in triglycerides

Question 23

What level of Acetyl-CoA would favor gluconeogenesis in the liver?

Answer 23

High Acetyl-CoA

High acetyl CoA inhibits pyruvate dehydrogenase and activates pyruvate carboxylase, stimulating conversion of pyruvate to oxaloacetic acid.

Question 25

Liver glycolysis vs gluconeogenesis diagram

Answer 25

Question 26

When the body is fasting for prolonged periods, fats provide the major energy source for the body, but do not directly provide \_\_\_\_\_

Answer 26

When the body is fasting for prolonged periods, fats provide the major energy source for the body, but do not directly provide **the carbon skeletons.** These are provided by **amino acids**.

Question 27

Pyruvate Carboxylase

Answer 27

Located in mitochondria

Question 28

Where is PEP Carboxykinase located?

Answer 28

The cytosol.

Question 29

Where is pyruvate carboxylase located?

Answer 29

The mitochondrion

Question 30

Pentose Phosphate Pathway from 10,000 ft

Answer 30

Question 31

Glucose monomers are added and removed from the ____ ends of the polymer

Answer 31

Glucose monomers are added and removed from the **“non-reducing”** ends of the polymer

Question 32

Why keep glucose-6-phosphatase in the ER?

Answer 32

1. It is not very specific, so it would interfere with other carbohydrate metabolism pathways 2. It is the same topology as the exterior, and it removes the G6P from the cytoplasm where it may exert inhibitory effects on the enzymes of glycogenolysis and gluconeogenesis.

Question 33

Glycogen phosphorylase in Type IIb skeletal muscle

Answer 33

Type IIb muscle lacks the glucagon receptor and has very little insulin sensitivity.

Question 34

Fates of Glucose-6-phosphate

Answer 34

Question 35

Hepatocyte Glycogen Stores

Answer 35

Glycogen-containing granules appear black by SEM

Question 36

Role of Pentose Phosphate Pathway in different tissues

Answer 36

Question 37

Activity of glycogen branching enzyme

Answer 37

Question 38

Phase I (Oxidate Phase) of Pentose Phosphate Pathway

Answer 38

Question 39

Glucose-6-phosphatase

Answer 39

Expressed only in liver, as only the liver needs export glucose from its glycogen stores.

Question 40

NADPH feedback inhibition

Answer 40

Question 41

Gluconeogenesis from 10,000 ft

Answer 41

Question 42

G6P is an allosteric regulator of ___ and \_\_\_.

Answer 42

G6P is an allosteric regulator of **glycogen synthase** and **glycogen phosphorylase**.

Question 43

Glycogen Phosphorylase Regulation in Muscle vs Liver

Answer 43

Question 44

\_\_\_ is the substrate used to make glycogen.

Answer 44

**UDP-glucose** is the substrate used to make glycogen. This is because glucose must be chemically activated in order to be coupled to an elongating glycogen molecule.

Question 45

Debranching of glycogen

Answer 45