Biochemical aspects of liver metabolism

Question 1

What is the main function of the liver?

Answer 1

First destination of most nutrients and xenobiotics
Bile production
Elimination of unwanted molecules
Secretion of plasma proteins e.g. albumin
Storage of important molecules - fuels, iron, vitamins
Regulation of metabolism

Question 2

How does the liver contribute to fuel storage?

Answer 2

Carbohydrate and lipid metabolism

Question 3

How does the liver contribute to the urea cycle?

Answer 3

Amino acid metabolism

Question 4

What are the different types of plasma proteins?

Answer 4

Albumin
Alpha globulins
Beta globulins
Gamma globulins - immunoglobulins

Question 5

What are the main functions of plasma proteins?

Answer 5

Maintenance of oncotic or colloid osmotic pressure 
Transport of hydrophobic substances
pH buffering
Enzymatic
Immunity

Question 6

What hydrophobic substances do plasma proteins transport?

Answer 6

Steroid hormones
Free fatty acids
Bilirubin
Cholesterol

Question 7

What is oncotic pressure?

Answer 7

Maintenance of fluids across the blood vessel wall helping to maintain the BP

Question 8

What is the function of alpha globulins?

Answer 8

Transport lipoproteins, lipids, hormones and bilirubin e.g. ceruloplasmin and retinol binding protein

Question 9

What is the function of retinol binding protein?

Answer 9

Transports vitamin A - lipid soluable alcohol converted to retinaldehyde
Deficiency causes visual impairement

Question 10

What is an example of a beta globulin?

Answer 10

Transferrin which transports iron and is an indicator of iron deficiency if low
Fibrinogen - inactive form of firbin which clots the blood

Question 11

What type of protein is albumin?

Answer 11

Small, negatively charged and water soluable

Question 12

What stimulates the production of albumin?

Answer 12

Insulin in repsonse to a meal will stimulate albumin production to transport fatty acids in blood plasma to allow you to metabolize ans store fatty lipids

Question 13

What will decrease the levels of albumin?

Answer 13

Liver disease

Starvation / low protein diet

Question 14

What does albumin transport?

Answer 14

Fatty acids
Bilirubin
Thyroid hormones
Drugs like aspirin

Question 15

What is iron the component of?

Answer 15

Haemoglobin
Myoglobin
Cytochromes

Question 16

How is iron transported in the blood?

Answer 16

As ferric ion Fe 3+ bound to transferrin

Question 17

How is iron stored in cells?

Answer 17

Ferritin

Question 18

How is copper transported around the body?

Answer 18

Bound to ceruloplasmin

Question 19

What is copper necessary for?

Answer 19

Regulation of redox reaction, transport and use of iron

Question 20

What makes up a lipoprotein?

Answer 20

Core of cholesterol esters and triglycerides and surrounded by phospholipids and apoproteins

Question 21

What is the function of lipoproteins?

Answer 21

Fat transport between organs and tissues

Question 22

What is the function of HDL?

Answer 22

Removes excess choleserol from cells and transports it back to the liver where it is excreted as bile salts via the biliary system or faeces

Question 23

What vitamins does liver store?

Answer 23

Vit A
Vit D
Vit B12

Question 24

How does the liver store iron?

Answer 24

Associated with ferritin

Comes from the breakdown of haemoglobin

Question 25

What is the purpose of cholesterol in cell membranes?

Answer 25

Increases rigitidy

Question 26

What is cholesterol the precursor of?

Answer 26

Bile acids Steroid hormones Vitamin D

Question 27

What is cholesterol metabolism important for?

Answer 27

Etiology of CV disease | Major component of gallstones

Question 28

How is cholesterol transported around the body?

Answer 28

30% free Majority is esterified to a wide range of long chain fatty acids where it is encorporated into lipoproteins and thereby solubilised

Question 29

Where is cholesterol stored?

Answer 29

Lipid droplets

Question 30

Where is the main site of liver synthesis?

Answer 30

Liver

Question 31

What does the synthesis of one mole of cholesterol require?

Answer 31

18mol of acetyl-coA 16 mol of NADPH 36 mol of ATP

Question 32

What does HMG-CoA reductase do?

Answer 32

Catalyses the irreversible formation of mevalonic acid

Question 33

What does vitamin D do?

Answer 33

Has a role in the regulation of calcium and phosphorus metabolism

Question 34

What are the 3 groups of steroid hormones?

Answer 34

Corticosteroids Androgens Estrogens

Question 35

What is the main metabolic product of cholesterol?

Answer 35

Bile salts which has a saturated steroid nucleus Stored as a component of bile in the gall bladder Acts as a detergent for emulsifying ingested lipids and recycled by enterohepatic circulation