Metabolic Functions of the Liver

Question 1

What are the fuel preferences of the liver?

Answer 1

Fatty acids, glucose, and amino acids

Question 2

What are the fuel preferences of adipose tissue?

Answer 2

Fatty acids

Question 3

What are the fuel preferences of skeletal muscle (at rest and during exercise)?

Answer 3

At rest: fatty acids

Exercising: glucose

Question 4

What are the fuel preferences of cardiac muscle?

Answer 4

Fatty acids

Question 5

What are the fuel preferences of the brain (fed and fasted states)

Answer 5

Fed: glucose
Fasted: Ketone bodies/glucose

Question 6

What are the steps of drug metabolism

Answer 6

1. Combine ingested drug with cytochrome P450(3+)
2. Reduce using NADPH-cytochrome P450 reductase to yield cytochrome P450(2+)-drug
3. Oxidize with O2 to cytochrome P450(2+)O2-drug
4. Form water by removing an oxygen to yield the oxidized form: cytochrome P450(3+)O-drug
5. Add -OH or -COOH to yield drug product-cytochrome P450(3+)
6. Release oxidized drug and cytochrome P450(3+)

Question 7

Why must a drug by oxidized to become hydrophilic/water soluble?

Answer 7

So that it can be excreted by the kidneys

Question 8

What, besides drugs, does cytochrome P450 catalyze oxidation of?

Answer 8

lipids, steroidal hormones, drugs, and toxic chemicals

Question 9

What is phase 2 of drug metabolism?

Answer 9

Oxidized drug product of phase 1 is conjugated with compounds (glucuronic acid, glycine, taurine, sulfate) to make it more hydrophilic

Question 10

Children and the elderly have LOW/HIGH drug metabolizing enzyme activity

Answer 10

Low

Question 11

What is the impact of undernutrition (insufficient metabolism) on drug metabolizing enzyme activity?

Answer 11

Decreases it

Question 12

What is the impact of polycyclic aromatic hydrocarbons in smoke on drug metabolizing enzyme activity?

Answer 12

Induces it

Question 13

How is retinol transported to the liver?

Answer 13

In chylomicrons as an ester of long-chain fatty acids

Question 14

How does the liver mobilize vitamin A when levels are low?

Answer 14

Hydrolyzes the retinol ester

Question 15

How is retinol secreted into the blood?

Answer 15

Retinol (result of retinol ester hydrolysis) binds to retinol-binding protein, which is secreted into the blood

Question 16

Where in the cell is retinol binding protein synthesized?

Answer 16

Rough ER

Question 17

Where is more than 80% of vitamin A stored in the body?

Answer 17

Hepatic cells

Question 18

How is vitamin D3 transported in the body?

Answer 18

In a non-esterified form via chylomicrons

Question 19

Where are major vitamin D stores found?

Answer 19

Adipose tissue and skeletal muscle

Question 20

What does the liver activate D3 to?

Answer 20

25 hydroxycholecalciferol by hydroxylation

Question 21

Vitamin D-binding protein is synthesized in the intestines, true or false?

Answer 21

False, it is synthesized in the liver

Question 22

What is the carrier of calcitriol

Answer 22

Vitamin D-binding protein

Question 23

Where is the major store of vitamin K?

Answer 23

sKeletal muscle

Question 24

What is the role of vitamin K in the hepatocyte?

Answer 24

Required for prothrombin synthesis, which is essential to clotting

Question 25

Iron is stored as _______

Answer 25

Ferritin

Question 26

What is the effect of iron on transferrin synthesis?

Answer 26

Inhibitory

Question 27

What does transferrin do?

Answer 27

Transport iron in the plasma

Question 28

What does the transferrin receptor do?

Answer 28

Move iron into the cell from the plasma

Question 29

What is the role of the liver in regards to copper?

Answer 29

1. store copper
2. take up copper
3. excrete copper into bile