Liver Function

Question 1

Define the ornithine cycle.

Answer 1

A series of biochemical reactions that can convert ammonia to urea

Question 2

List the functions of the liver.

Answer 2

Control of blood glucose levels, amino acid levels and lipid levels
Synthesis of bile, plasma proteins and cholesterol
Synthesis of red blood cells in the fetus
Storage of vitamins A,D and B12, iron and glycogen
Detoxification of alcohol and drugs
Breakdown of hormones
Destruction of RBC

Question 3

How many grams of glycogen is the liver able to store?

Answer 3

100-120g

Question 4

How is the glycogen stored in the liver?

Answer 4

Glycogen forms granules in the cytoplasm of the hepatocytes.

Question 5

Give an example of a substance that has to be broken down by the liver that is produced by the body.

Answer 5

Hydrogen peroxide

Question 6

Give an example of a toxic substance that is consumed into the body.

Answer 6

Alcohol, medicinal drugs, recreational drugs.

Question 7

How are toxins rendered harmless by the liver?

Answer 7

Oxidation, reduction, methylation or by combination with other molecules.

Question 8

What does catalase do?

Answer 8

Converts hydrogen peroxide to oxygen and water.

Question 9

What does cytochrome P450 do?

Answer 9

A group of enzymes used to breakdown drugs including cocaine and various medicinal drugs.

Question 10

What is alcohol broken down into during the detoxification of alcohol?

Answer 10

Ethanol -> Ethanal -> Ethanoic acid -> Acetate -> Acteyl CoenzymeA which follows into respiration

Question 11

Which enzyme breaks down ethanol into ethanal?

Answer 11

Ethanol dehydrogenase

Question 12

Which enzyme breaks down ethanal into ethanoic acid?

Answer 12

Ethanal dehydrogenase

Question 13

What happens if the liver has to oxidise too much alcohol?

Answer 13

It’s supplies of NAD are all used up which means that it cannot break down fatty acids. The fatty acids are then broken down into lipids and stored in the liver which can lead to fatty liver disease, alcohol-related hepatitis or cirrhosis.

Question 14

Why can’t excess amino acids be stored?

Answer 14

Their amino group makes them toxic.

Question 15

What are the two processes that amino acids undergo to be turned into urea?

Answer 15

Deamination and the ornithine cycle

Question 16

Give the word equation for deamination.

Answer 16

Amino acid + oxygen -> keto acid + ammonia

Question 17

Describe the ornithine cycle.

Answer 17

Ammonia + CO2 + ornithine - H2O -> Citrulline
Citrulline + ammonia - H2O -> Arginine 
Arginine + H2O -> urea
Arginine - Urea = ornithine 
(the cycle begins again)