Biochem of the Liver

Question 1

where does the liver excrete unwanted molecules

Answer 1

into biliary tree and faecal excretion

Question 2

name a plasma protein

Answer 2

albumin

Question 3

why is faeces white in end stage liver disease

Answer 3

as liver not breaking down haem into bilirubin

Question 4

how does the liver regulate metabolism

Answer 4

fuel storage- carbohydrate and lipid metabolism

urea cycle- amino acid metabolism

Question 5

what does electrophoresis do

Answer 5

separates proteins by size

Question 6

name the different plasma proteins

Answer 6

albumin, alpha gamma and beta globulins (gamma globlins= immunoglobulins)

Question 7

what colour is plasma

Answer 7

straw coloured

Question 8

what are the main functions of plasma proteins

Answer 8

maintain oncotic or collois osmotic pressure (maintains fluid balance across vessels walls)

transports hydrophobic substances

pH buffering

enzymatic

immunity

Question 9

what hydrophobic substances do plasma proteins transport

Answer 9

steroid hormones, free fatty acids, bilirubin, cholesterol

Question 10

give an example of the enzymatic actions of plasma proteins

Answer 10

blood clotting

Question 11

what does albumin do

Answer 11

controls oncotic pressure ans transports hydrophobic substances

Question 12

what do alpha globulins do (e.g ceruloplasmin)

Answer 12

transport lipoproteins, lipids, hormones and bilirubin

is a retinal binding protein , transports vitamin A

Question 13

what does a deficiency in vitamin A cause

Answer 13

visual impairment

Question 14

name two beta globulins and their functions

Answer 14

transferrin- transports Fe3+, indicator of iron deficiency

fibrinogen- inactive form of fibrin, clotting of blood

Question 15

what is the most abundant plasma protein

Answer 15

albumin

Question 16

what stimulates the production of albumin

Answer 16

insulin and nutrient intake

Question 17

when are albumin levels low

Answer 17

liver disease or starvation

Question 18

what is albumins affinity and capacity for hydrophobic molecules

Answer 18

low affinity but high capacity

Question 19

what endogenous lipophilic substances does albumin transport

Answer 19

fatty acids, bilirubin, thyroid hormone

Question 20

what exogenous substances does albumin transport

Answer 20

drugs with weak hydrophobic capacity e.g. aspirin

Question 21

where is iron stored

Answer 21

in cells bound to ferritin

Question 22

why is iron important

Answer 22

component of haemoglobin, myoglobin, cytochromes

Question 23

what in the blood transports copper

Answer 23

ceruloplasmin

Question 24

what does a deficiency in ceruloplasmin result in

Answer 24

wilsons disease

Question 25

what are steroid hormones derived from

Answer 25

cholesterol

Question 26

which steroid hormones are hydrophobic

Answer 26

T3/4

Question 27

how are steroid hormones transported in the circulation

Answer 27

via transport molecules - thyroxine bound to thyroid-binding globulin - cortisol bound to cortisol-binding globulin

Question 28

why are transport molecules essential for steroid hormones

Answer 28

as would be eliminated by liver or kidney without them

Question 29

describe the structure of a lipoprotein

Answer 29

core of hydrophobic lipids (cholesterol esters, triglycerides) surrounded by a shell of polar lipids (phospholipids) and apoproteins

Question 30

what is the role of lipoproteins

Answer 30

fat and cholesterol transport between organs and tissues

Question 31

what is the function oh HDL

Answer 31

reverse cholesterol transport- removes excess cholesterol from cells (cholesterol esterified with fatty acids, transported back to liver, excreted as bile salts via biliary tree of faeces)

Question 32

what is the only organ capable of metabolising and excreting cholesterol

Answer 32

the liver

Question 33

what vitamins does the liver store

Answer 33

A, D and B12

Question 34

where does iron stored in the liver come from

Answer 34

haemoglobin

Question 35

what does cholesterol do to cell membranes

Answer 35

increases rigidity- good thing

Question 36

what is cholesterol pre cursors of

Answer 36

bile acids, steroid hormones, vit D

Question 37

is cholesterol soluble in water

Answer 37

no- especially if esterified to a long chain fatty acid

Question 38

how is cholesterol solubilised

Answer 38

via incorporation into lipoproteins- located in core of molecule

Question 39

where is the main site of cholesterol synthesis

Answer 39

liver

Question 40

what does HMG-CoA reductase

Answer 40

catalyses the irreversible formation of mevalonic acid- rate limiting enzyme in cholesterol synthesis

Question 41

what increases and reduces the activity of HMG-CoA reductase and therefore the synthesisi of cholesterol

Answer 41

increased by fasting decreased by dietary cholesterol also controlled by hormones

Question 42

what is the role of vit D (a product from cholesterol)

Answer 42

regulation of calcium and phosphorus metabolism

Question 43

what steroid hormones are made from cholesterol

Answer 43

corticosteroids androgens astrogens

Question 44

what organ makes each steroid hormones from cholesterol

Answer 44

corticosteroids- adrenal cortex androgens- testis estrogens- ovary

Question 45

what is the main metabolic product from cholesterol

Answer 45

bile salts

Question 46

where are bile salts synthesised and secreted from

Answer 46

the liver

Question 47

where are bile salts stored

Answer 47

in gall bladder as component of bile

Question 48

how are bile salts recycled

Answer 48

by the enterohepatic circulation

Question 49

what do anion exchange resins do and how does it affect cholesterol

Answer 49

bind bile salts and inhibit re-absorption in the enterohepatic circulation- increased synthesis and excretion, conversion of cholestrol in the liver is decreased, uptake of LDL is increased as numbers of LDL receptors increased= lower plasma LDL