Functions of the liver

Question 1

How does the liver control carbohydrate metabolism?

Answer 1

• hepatocytes are closely involved in the homeostatic control of glucose levels in the blood by their interaction with insulin and glucagon
• when blood glucose levels rise and stimulate heptacytes to convert glucose to the storage carbohydrate glycogen
• when blood sugar levels start to fall, the hepatocytes convert glycogen back to glucose under the influence of the hormone glucagon

Question 2

What do hepatocytes synthesise?

Answer 2

most of the plasma protein

Question 3

What is transamination?

Answer 3

• the conversion of one amino acid to another
• hepatocytes do this
  
  • important because the diet does not always contain the required balance of amino acid but transamination can overcome problems this might cause

Question 4

What is deamination simply?

Answer 4

the removal of an amine group from a molecule

Question 5

Why must deamination occur?

Answer 5

the body cannot store either proteins or amino acids

any excess ingested protein would be excreted and therefore wasted if it were for the action of the hepatocytes

Question 6

How does deamination occur>

Answer 6

• first converting into ammonia
  
  • toxic
• then to urea
  
  • toxic in high conc but not in conc found in blood

Question 7

What is done with the remainder of amino acid?>

Answer 7

can be fed into cellular respiration or converted into lipids for storage

Question 8

What is the ornithene cycles?

Answer 8

the ammonia produced in the deamination is converted into urea in a set of enzyme controlled reactions known as the ornithene cycle

Question 9

Draw the ornithene cycle

Answer 9

Question 10

How are toxins produced?

Answer 10

• level of toxins always tends to increase
• other metabolic pathways produce potentially posionous substance
• we also voluntarily take a wide variety of toxins such as alcohol or other drugs

Question 11

How is hydrogen peroxide broken down?

Answer 11

• H2O2 is a by-product of various metabolic pathways in the body
• hepatocytes contain the enzyme catalase
• catalase splits hydrogen peroxide into oxygen and water

Question 12

How is alcohol broken down?

Answer 12

• hepatocytes contain the enzyme alcohol dehydrogenase that breaks down the ethanol to ethanal
• ethanal is converted to ethanoate which may be used to build up fatty acids or used in cellular respiration

Question 13

what is 1 2 and 3

Answer 13

1. central vein and lobule
2. sinusoids
3. hepatocytes

Question 14

Answer 14

1. hepatocyte
2. red blood cells within sunusoids
3. mitochondria
4. Kupffer cells

Question 15

What is Cirrhosis ?

Answer 15

• disease where normal liver tissue is replaced by fibrous scar tissue
• many causes e.g.
  
  • hep c
  • mainly alcohol
  • genetic conditions

Question 16

where does the liver store glycogen?

Answer 16

• stores it as granules in cells

Question 17

What is detoxification?

Answer 17

• harmful compounds broken down into less harmful compounds