The Liver

Question 1

What is a hepatocytes?

Answer 1

A liver cell

Question 2

Why is it essential for good blood supply in liver?

Answer 2

Very metabolically active cells, important role in homeostasis - metabolism reaction generate heat, maintain glucose levels

Question 3

Which sources supply liver with blood?

Answer 3

Oxygenated blood from the heart, oxygen for aerobic respiration, very active. From hepatic artery
Deoxygenated blood from digestive system, through hepatic portal vein, rich in products of digestion, uncontrolled concentrations, may be toxic

Question 4

What is the hepatic portal vein?

Answer 4

Unusual blood vessel that has capillaries at both ends, carries blood from digestive system to the liver, products uncontrolled concentration so removal of excess amino acids, glucose, alcohol etc

Question 5

What vessel does blood leave liver from?

Answer 5

Hepatic vein that rejoins the vena cava

Question 6

What is the fourth vessel in the liver?

Answer 6

Bile duct, bike secretes from liver cells into bile duct, carries it to gall bladder where it is stored to be used to digest fats in the small intestines

Question 7

How are cells in the liver arranged?

Answer 7

Arranged to ensure maximum contact with blood, divided into lobes, further divided into lobules, hepatic vein and portal vein enter liver, split into small vessels, inter lobular. At intervals, branch off and enter lobules, blood mixed, and passes into sinusoid, lined with liver cells. Sinusoid empties into the intralobular vessel, branch of hepatic vein, branches join together to form hepatic vein, drains blood from the liver

Question 8

What is the role of the sinusoid?

Answer 8

Runs through lobules, ensures blood comes into close contact with liver cells, so they can remove and pass molecules into the blood

Question 9

How is bile moved through the liver?

Answer 9

Manufacture bile, released into bile canaliculi, join together to form bile duct, which transports bile to gall bladder

Question 10

Outline passage of blood through liver

Answer 10

Hepatic portal vein and hepatic artery bring blood in, split into inter lobular vessels, branch and enter lobules, into sinusoid, drains into intra lobular vessel, join to form hepatic vein to drain out if liver

Question 11

How are liver cells specialised?

Answer 11

Hepatocytes, cuboidal, micro villi to increase SA, many metabolic functions, so cytoplasm is very dense, specialised in amounts of organelles

Question 12

What are the metabolic functions of the liver?

Answer 12

Protein synthesis
Carbohydrate storage
Protein synthesis
Cholesterol synthesis
Bike salts
Detoxification

Question 13

What are kupffer cells?

Answer 13

Specialised macrophages that move in sinusoids and involved in breakdown of old red blood cells, bilirubin produced haemoglobin break down, rexcreted in bile and faeces

Question 14

What are the functions of the liver?

Answer 14

Control of blood glucose, amino acids, lipid levels
Synthesis of red blood cells in fetid, bile, plasma proteins, cholesterol
Storage of vitamins and glycogen
Detoxification if alcohol and drugs
Breakdown of hormones
Destruction of red blood cells

Question 15

What is urea?

Answer 15

Excretory product formed from the breakdown of excess amino acids

Question 16

How is urea formed?

Answer 16

Excess amino acids cannot be stored, so deamination in liver so rest of molecule can be removed and toxic amine group removed, undergoes rearmed t by deamination and ornithine cycle

Question 17

What is the equation for deamination?

Answer 17

Produces highly toxic ammonia, cannot accumulate, and Keto acid
Ammonia + Oxygen > Keto acid + NH3

Question 18

What is the ornithine cycle?

Answer 18

Process in which ammonia is converted to urea, occurs partly in cytosol and partly in mitochondria, unread less soluble and less toxic, taken to kidneys, filtered out if blood and stored in bladder, concentrated as urine

Question 19

Why is equation for ornithine cycle?

Answer 19

2 Ammonia + CO2 > Urea +H2O

Urea is CO(NH2)2
Cycle is ornithine, plus ammonia and co2, which makes citrulline, then another ammonia added to make arginine, water added to make urea and regenerate ornithine

Question 20

What is detoxification?

Answer 20

Conversion of toxic molecules to less toxic or non toxic molecules, such as h2o2, alcohol, drugs, rendered harmless by oxidation, reduction, methylation or combination with another molecule. Liver cells contain many enzymes for these reactions

Question 21

What does catalase do?

Answer 21

H2o2 to oxygen and water

Question 22

Outline detoxification of alcohol

Answer 22

Alcohol depresses nerve activity and has energy that can be used in reputation, so broken down by action of ethanol dehydrogenase to ethanal, then ethanal dehydrogenase used to break down to ethanoic acid, final product is ethanoate(acetate), which combines with coenzyme A enters respiration. Hydrogen a released accepted by NAD to form reduces NAD

Question 23

How does alcohol cause problems in the liver?

Answer 23

NAD also required to oxidise and breakdown fatty acids for respiration, but insufficient NAD if too much alcohol detoxification, so fatty acids converted back to lipids and stored in hepatocytes, causing liver to enlarge, fatty liver, can lead to hepatitis or cirrhosis

Question 24

why might different by products be produced from breakdown of drugs?

Answer 24

Slightly different enzymes so so break down substrate in different way, different enzymes from genetic variation, everyone has different alleles to produce slightly different alleles

Question 25

Why is there high concentration of mitochondria on the hepatocytes?

Answer 25

Provide ATP for energy requiring processes such as protein synthesis, ribosomes manufacture many enzymes needed in liver cell