The Liver: Functions

Question 1

What are the 6 main functions of the liver?

Answer 1

Controls blood glucose, amino acid and lipid levels, synthesises RBC in foetus, bile, plasma proteins and cholesterol, stores vitamin A, D , B12, iron, glycogen, detoxification of drugs and alcohol, hormone breakdown, RBC destruction

Question 2

How many grams of protein do we need every day?

Answer 2

40-60g, most people in developed countries get more than this

Question 3

What is the ornithine cycle?

Answer 3

Process where ammonia is converted to urea (combined with CO2), partly in the cytosol and partly in mitochondria (ATP is used)

Question 4

What is the chemical summary of the ornithine cycle?

Answer 4

Ammonia + CO2 -> urea and water

Question 5

What is a compound that the liver detoxifies which is produced by the body?

Answer 5

Hydrogen peroxide

Question 6

How can toxins be rendered harmless?

Answer 6

Oxidation, reduction, methylation or combination with another mol

Question 7

What are the enzymes that liver cells have in them to make toxic mols less toxic?

Answer 7

Catalase: converts hydrogen peroxide to O2 and H2O, high turnover number: 5million H peroxide mols that can be made harmless in a minute

Question 8

What are the 3 stages of the ornithine cycle?

Answer 8

Ornithine, citrulline, arginine

Question 9

What is ethanol?

Answer 9

Drug that depresses nerve activity, contains chemical potential energy (can be used in respiration)

Question 10

What happens to ethanol in the liver cells?

Answer 10

Broken down by enzyme ethanol dehydrogenase, makes ethanal, broken down by ethanal dehydrogenase, final compound = ethanoate (acetate)

Question 11

What happens to ethanoate (acetate) –product of ethanol breakdown?

Answer 11

Combined with coenzyme A = acetyl coenzyme A which enters respiration process, H ions released combine with NAD (coenzyme) = reduced NAD

Question 12

What is NAD required for?

Answer 12

To oxidise and break down fatty acids for use in respiration, if the liver has to detoxify lots of alcohol it has insufficient NAD

Question 13

What happens if there is insufficient NAD in the liver?

Answer 13

Fatty acids not broken down so converted back to lipids and stored in hepatocytes, liver becomes enlarged: fatty liver, leads to alcohol-related hepatitis or cirrhosis

Question 14

What large group of enzymes do liver cells contain? What do these enzymes do?

Answer 14

Cytochrome P450, breakdown toxic mols like cocaine, most concentrated in endoplasmic reticulum