Regulation of Carbohydrate Metabolism

Question 1

what is the reasoning for regulating metabolism in the fasting state?

Answer 1

• maintain blood glucose levels via gluconeogenesis, glycogenolysis, and TAG mobilization

Question 2

what are the fed state pathways? where do they occur?

Answer 2

glycolysis- all
glycogen synthesis- liver, muscle
fatty acid/TAG synthesis- liver
TAG storage- adipose
pentose shunt- liver
PDH- liver and aerobic tissue

Question 3

what are the fasting state pathways?

Answer 3

gluconeogenesis- liver
glycogenolysis- liver (muscle)
lipolysis- adipose
fatty acid oxidation- muscle, liver
ketone body formation- liver
ketone body use- muscle, brain

Question 4

what is necessary for TAG mobilization?

Answer 4

mitochondria- need TCA cycle

Question 5

what is glucagon? what controls it? where does it act?

Answer 5

fasting state hormone
released in response to decreased insulin
acts on liver (adipose has a few receptors)

Question 6

what does glycogen do?

Answer 6

decreases glucose uptake by removing GLUTs from membranes and putting them back into vesicles

Question 7

what is special about liver GLUTs?

Answer 7

low affinity for glucose
glucose is only taken up when concentration is really high (immediately after meals)
GLUTs are not responsive to insulin, only glucose concentration

Question 8

what energy source does the liver use between meals?

Answer 8

fatty acid oxidation

glycolysis is turned off to conserve glucose coming from gluconeogenesis and glycogenolysis

Question 9

what does phosphorylase b kinase do? what activates it?

Answer 9

phophorylates glycogen phosphorylase b to a (activates glycogen phosphorylase)
phosphorylated in the presence of glucagon

Question 10

what does protein pohsphatase do? what activates it?

Answer 10

dephosphorylates glycogen phosphorylase a to b (deactivates glycogen phosphorylase)
dephosphorylated in the presence of insulin (activated)

Question 11

how does insulin control enzymes

Answer 11

dephosphorylates things to result in glycogen synthesis

Question 12

how does glucagon/epinepherine regulate things?

Answer 12

phosphorylates things to degrade glycogen

Question 13

what is the key control point in mitochondrial pyruvate metabolism?

Answer 13

at the pyruvate dehydrogenase/pyruvate carboxylase branch point
fasting state- PC is activated, PDH off
fed state- PDH activated, PC off

Question 14

what inhibited pyruvate dehydrogenase?

Answer 14

acetyl-CoA

NADH

Question 15

what stimulates the fasting state route for pyruvate?

Answer 15

high FA oxidation (lots of NADH and FADH2 and acetylCoA)

Question 16

what happens to excess acetyl CoA?

Answer 16

turned into ketone bodies in the liver

Question 17

what are the goals of PDH deficiency?

Answer 17

treat acidosis
lower lactate production
increase lactate use

Question 18

what is a ketogenic diet?

Answer 18

low carb, high fat and protein
shifts to usage of TAGs due to low glucose
high energy burring because glucose comes from glycogenolysis and gluconeogenesis
lactate is primary carbon source

Question 19

what can be used to get pyruvate?

Answer 19

lactate and alanine