liver

Question 1

what is excretion

Answer 1

• removal of waste products of metabolism from the body

Question 2

main metabolic waste products in mammals

Answer 2

• CO2 : from cellular respiration + excreted from lungs
• bile pigments : breakdown of Hb from old RBC in the liver + excreted in the bile via gall bladder.
• urea : break down of excess Aa from liver + excreted by kidneys in urine.

Question 3

what is a hepatocyte

Answer 3

• cells that make up most of liver

- carries out most of homeostatic functions of the liver

Question 4

structure of the liver

Answer 4

• hepatocytes have large nuclei (active DNA transcription) , Golgi apparatus (protein packaging and modification) and lots of mitochondria (active)
• metabolically active cells
• they can divide and replicate
• blood from the hepatic artery and the hepatic portal vein are mixed in sinusoids (spaces surrounded by hepatocytes)
• the mixing increases oxygen content of the blood from HPV
• supplies hepatocytes with enough O2 for needs
• sinusoids have Kupffer cells which are the macrophages of the liver
• they ingest foreign particles and help protect against disease
• bile , from the breakdown of blood, is secreted from the hepatocytes into canaliculi.
• bile drains into bile ductules and then taken to the gall bladder.

Question 5

how is the liver adapted for its function

Answer 5

• blood from HPV brings products of digestion and cell metabolism to the liver
• blood from HA bring o.blood to the liver
• blood from HPV and HA combine in sinusoids
• giving raw materials and oxygen to hepatocytes.
• Kupffer cells act as macrophages and ingest foreign particles and protect from disease.
• HPV removes deoxygenated blood carrying detoxification products (urea away from liver)

Question 6

how does the liver control carbohydrate metabolism

Answer 6

• when BGC rises, insulin levels rise
• hepatocytes are stimulated to convert glucose into glycogen
• when BGC falls, glucagon levels rise
• hepatocytes convert the glycogen back into glucose.

Question 7

deamination of excess Aa

Answer 7

• remove and amine group from a molecule
• convert into ammonia and then into urea
• urea is toxic in high concentrations
• the urea is excretes by the kidneys
• any excess Aa are used in cellular respiration
• ## converted into lipids for storage

Question 8

transamination

Answer 8

• the conversion of one Aa into another

- overcomes problems of not having the required balance of Aa in a diet

Question 9

ornithine cycle

Answer 9

• set of enzyme controlled reactions

- where the ammonia produced in deamination is converted into urea

Question 10

detoxification

Answer 10

• liver can detoxify substances
• breakdown of hydrogen peroxide
• by product of metabolic pathways in the body
• hepatocytes contain catalase which split hydrogen peroxide into oxygen + water
• liver breaks down ethanol (drinks)
• hepatocytes have alcohol dehydrogenase
• ethanol broken down into ethanal
• ethanal converted into ethanoate
• ethanoate can be used in cellular respiration/build up of fatty acids.
• Ethanol is absorbed and concentrated in the liver so an excess of toxic ethanol could affect liver cells first.