4B- Fed and Fasted States

Question 1

1. Describe the general metabolism of glucose, fats, and proteins in the fed state following their absorption from the digestive tract into the following tissues: liver, brain, red blood cell, muscle and adipose tissue.

Answer 1

Question 2

What does insulin do in the fed state?

Answer 2

in the fed state, insulin allows glucose uptake into msucle and adipose tissues

muscle uses the glucose to replenish glycogen storage

adipose oxidize glucose for energy and also use glucose as the source of glycerol of triglycerides they store

Question 3

How are blood glucose levels maintained during a short term fast (up to 12h)?

talk about the pancreas, liver and adipose tissue

Answer 3

2 hours after eating, blood glucose levels drop so the pancreas stops secreting insulin and starts secreting glucagon

the liver starts to degrade its glycogen stores (glycogenolysis) and release glucose into the blood

it also goes through gluconeogenesis by converting noncarbohydrate precursors (lactate, glycerol, and amino acids) into glucose

when insulin drops, glucagon rises and adipose tissues undergo lipolysis which coverts fatty acids into glycerol, which enter the blood.

most of the fatty acids undergo beta-oxidation into acetyl-CoA’s for the

Question 4

How are blood glucose levels maintained during a prolonged fast (starvation)?

Answer 4

muscle decreases its use of ketone bodies and depends mainly on fatty acids for fuel

liver continues to covert fatty acids into ketone bodies to supply the brain. it also makes free glucose (by guconeogenesis) for RBC’s and a little for the brain.

adipose tissue continues to break down TG’s for FA’s and glycerol for fuel.

Question 5

Provide a summary of fasting

Answer 5

Question 6

Provide a summary of fasting for days

Answer 6

Question 7

What metabolic pathways are active in the liver?

Answer 7

gluconeogenesis

glycogenolysis

TCA

glycolysis

glycogen synthesis

beta-oxidation

Question 8

What metabolic pathways are active in the brain?

Answer 8

glycolysis

TCA

Question 9

What metabolic pathways are active in the RBC?

Answer 9

only glycolysis

Question 10

What metabolic pathways are active in the muscle?

Answer 10

TCA

glycolysis

proteolysis

glycogenolysis

glycogen synthesis

Question 11

What metabolic pathways are active in the adipose tissue?

Answer 11

lipolysis

lipogenesis

Question 12

What are the 3 ketone bodies?

Answer 12

Ketone bodies are produced from excess acetyl-CoA when fatty acids are broken down, making:

acetone, acetoacetic acid, and beta-hydroxybutyric acid

Question 13

Which 2 ketone bodies can be used as energy?

Answer 13

acetoacetate and beta-hydroxybutyrate can be reconverted to acetyl-CoA to produce energy, via the citric acid cycle.