15.4 Excretion, Homeostasis + The Liver

Question 1

What are the main metabolic waste products in mammals? How are they formed?

Answer 1

• CO2, formed in cellular respiration
• Bile Pigments, formed from the breakdown of haemoglobin in the liver
• Urea, formed from the breakdown of excess amino acids in the liver

Question 2

How is blood delivered to and taken from the liver?

Answer 2

the HEPATIC ARTERY carries blood to the liver
the HEPATIC VEIN carries blood to the heart
the liver is also supplied with blood by the intestines by the HEPATIC PORTAL VEIN (which carries products of digestion for the liver to use)

Question 3

Cell structure of the liver

Answer 3

Liver cells, or HEPATOCYTES, are relatively simple in design, they have large nuclei, prominent Golgi apparatus and a large volume of mitochondria, so are largely metabolically active

Question 4

Structure of the liver

Answer 4

• blood from hepatic artery and portal vein is mixed into spaces called SINUSIODS, which are lined with hepatocytes
• sinusoids contain KUPPFER CELLS which act as resident macrophages to the liver

Question 5

Function of hepatocytes

Answer 5

these cells secrete bile into spaces called CANALICULI, from here bile is drained into the bile ducts and transported to the gall bladder

Question 6

Functions of the Liver:

CARBOHYDRATE METABOLISM

Answer 6

when blood glucose levels rise so do insulin levels, stimulating hepatocytes to convert glucose to glycogen for storage.

Question 7

Functions of the Liver:

DEAMINATION of Excess Amino Acids

Answer 7

this is the removal of an amine group from a molecule. the body cannot store the amino acids and so would be excreted unless this deamination occurred. the convert the amine group into ammonia and then urea through a process known as the ORNITHINE CYCLE

Question 8

What is the ORNITHINE CYCLE?

Answer 8

this is the enzyme-controlled cycle of the production of urea through the deamination of proteins

Question 9

Functions of the Liver:

DETOXIFICATION

Answer 9

The liver is a site where poisonous substances are taken to be made harmless through detoxification
An example would be the breakdown of H2O2 via the enzyme catalase producing harmful water and oxygen