13. Post Absorption Processing of Carbohydrates

Question 1

What is the hormonal response to being in the fed state?

Answer 1

Increased insulin

Decreased glucagon

Question 2

What is the response of organs to being in the fed state?

Answer 2

Liver makes glycogen, proteins, TAGs
Adipose makes TAGs
Muscle makes protein

Question 3

What is the hormonal response to being in the fasting state?

Answer 3

Decreased insulin

Increased glucagon and adrenaline

Question 4

What is the liver’s response to the fasting state?

Answer 4

Glycogenolysis
Gluconeogenesis
B-oxidation
Ketogenesis

Question 5

What is adipose tissue’s response to the fasting state?

Answer 5

Lipolysis

Question 6

What is the muscle’s response to the fasting state?

Answer 6

Use FAs and ketones as fuel

Proteolysis to supply the liver with AAs

Question 7

What is gluconeogenesis?

Answer 7

Synthesis of glucose from lactate, pyruvate and glycerol

Question 8

What is gluconeogensis stimulated by?

Answer 8

Glucagon

Question 9

What enzymes are involved in gluconeogenesis?

Answer 9

Pyruvate carboxylase
PEP carboxykinase
Fructose-1,6-bisphosphate
Glucose-6-phosphatase

Question 10

What is the structure of glycogen?

Answer 10

a-D glucose units joined by a-1,4 glycosidic bonds

Question 11

What type of bonds attach chains to glycogen?

Answer 11

a-1,6 glycosidic bonds

Question 12

What is the function of glycogen synthase?

Answer 12

Adds units to the non-reducing ends of growing chains of glucose

Question 13

What enzyme is used if there is no remaining glycogen?

Answer 13

Glycogenin

Question 14

What adds branches to glycogen?

Answer 14

Branching enzyme

Question 15

What are the steps in glycogenolysis?

Answer 15

1. Glycogen phosphorylase cleaves a-1,4 glycosidic bonds
2. Glucose units are released as glucose-1-phosphate
3. GP stops 4 glucose residues before each branch point, creating limit dextrins
4. Branches are removed by debranching enzyme

Question 16

What converts glucose-1-P to glucose-6-p?

Answer 16

Phosphoglucomutase

Question 17

What happens to glucose-6-P in the liver?

Answer 17

Converted to glucose by glucose-6-phosphatase
Requires glucose-6-P translocase
Released into the bloodstream

Question 18

What happens to glucose-6-P in muscle?

Answer 18

Goes into glycolysis

Question 19

What is the allosteric regulation of glycogen breakdown?

Answer 19

Glucose-6-P increases glycogen synthase and decreases glycogen phosphorylase
Ca++ released by muscle contraction, increased AMP (muscle anoxia) and low ATP increase glycogen phosphorylase

Question 20

What are the effects of glucagon and adrenaline on glycogen breakdown?

Answer 20

Activate cAMP dependent PkA to cause phosphorylation

Activates GP and inactivates GS to cause glycogen breakdown

Question 21

What effect does insulin have on glycogen breakdown?

Answer 21

Causes dephosphorylation
Increase GS, decrease GP
Glycogen synthesis

Question 22

What enzyme is deficient in McArdle Disease?

Answer 22

Muscle Glycogen Phosphorylase Deficiency

Question 23

What are symptoms of McArdle Disease?

Answer 23

Muscle fatigue

Myoglobinuria

Question 24

What enzyme is deficient in Von Gierke’s Disease?

Answer 24

Glucose-6-Phosphatase

Question 25

What are symptoms of Von Gierke’s Disease?

Answer 25

Hypoglycaemia
Lactic acidosis
Ketosis
Hepatomegaly