15.4 Excretion, Homeostasis And The Liver

Question 1

What is excretion?

Answer 1

The removal of metabolic waste products from the body 
E.g.
- carbon dioxide 
- urea
- bile pigments

Question 2

What is the structure of a liver lobule?

Answer 2

Kupffer cells - specialised macrophages in the liver where haemoglobin is broken down. The line the bile canaliculus

Bile canaliculus - the hepatocytes secrete bile into these canaliculi and from there it drains into the gall bladder to be stored

Sinusoids - where blood from the hepatic portal vein and the hepatic portal artery mix

Question 3

What are hepatocytes?

Answer 3

Liver cells

Question 4

What are the function of the liver?

Answer 4

Deamination
Transanimation
Glycogen storage
Detoxification 
Carbohydrate Control

Question 5

What is deamination?

Answer 5

The removal of an amine group from a molecule

Question 6

What is transamination?

Answer 6

The conversion of one amino acid to another

Question 7

What is glycogen storage?

Answer 7

• glucose is converted to glycogen in the hepatocytes

- glycogen stores are hydrolysed to glucose when required

Question 8

What is detoxification?

Answer 8

When a metabolic waste products is converted into a useful or less harmful waste product

e. g. hydrogen peroxide —> water and oxygen by catalase
e. g. ethanol —> ethanal by alcohol dehydrogenase

Question 9

What is carbohydrate Control?

Answer 9

When blood glucose levels rise, insulin levels get hjgh and stimulate hepatocytes to convert glucose to the storage carbohydrate glycogen

When blood glucose levels fall, insulin levels rise and the hepatocytes convert glycogen back to glucose under the influence of glucagon

Question 10

How is blood supplied to the liver?

Answer 10

1. The hepatic artsy supplies oxygenated blood from the heart
2. The hepatic portal vein supplies blood carrying glucose, amino acids and fats from the small intestine