9.4 Metabolism and the liver

Question 1

What is metabolism

Answer 1

The sum of all the reactions that take place in a cell or in the body

Question 2

What are examples of metabolic reactions

Answer 2

• Conversion of glucose to starch, glycogen and cellulose
• formation of lipid molecules from glycerol and three fatty acid molecules
• use of glucose and nitrate ions to form amino acids that are then used to make proteins
• respiration
• photosynthesis
• breakdown of excess proteins in the liver to form urea

Question 3

What metabolic reactions does the liver do

Answer 3

• detoxifying poisonous substances
• passing the breakdown products into the blood so they can be excreted in the urine via the kidneys
• breaking down old, worn out blood cells and storing the iron until it is needed to synthesise more blood cells

Question 4

What does the liver do with lactic acid

Answer 4

Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose

Question 5

How is the oxygen debt repaid

Answer 5

The oxygen debt is repaid once the lactic acid has been converted back to glucose and it has been completely broken down in aerobic respiration to form carbon dioxide and water

Question 6

What happens if glucose is not needed

Answer 6

Converted to glycogen and stored in the liver until its needed

Question 7

What does the hepatic vein do

Answer 7

Carries blood from the liver on to the heart with levels of food adjusted

Question 8

What does the hepatic artery do

Answer 8

Brings oxygenated blood to the liver

Question 9

What does the hepatic portal vein do

Answer 9

Carries blood containing digested food from the intestines to the liver

Question 10

What are the roles of the liver

Answer 10

• Produces bile to raise the pH