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GI > Biochem of the Liver > Flashcards

Biochem of the Liver Flashcards

1
Q

where does the liver excrete unwanted molecules

A

into biliary tree and faecal excretion

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2
Q

name a plasma protein

A

albumin

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3
Q

why is faeces white in end stage liver disease

A

as liver not breaking down haem into bilirubin

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4
Q

how does the liver regulate metabolism

A

fuel storage- carbohydrate and lipid metabolism

urea cycle- amino acid metabolism

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5
Q

what does electrophoresis do

A

separates proteins by size

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6
Q

name the different plasma proteins

A

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

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7
Q

what colour is plasma

A

straw coloured

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8
Q

what are the main functions of plasma proteins

A

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

transports hydrophobic substances

pH buffering

enzymatic

immunity

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9
Q

what hydrophobic substances do plasma proteins transport

A

steroid hormones, free fatty acids, bilirubin, cholesterol

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10
Q

give an example of the enzymatic actions of plasma proteins

A

blood clotting

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11
Q

what does albumin do

A

controls oncotic pressure ans transports hydrophobic substances

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12
Q

what do alpha globulins do (e.g ceruloplasmin)

A

transport lipoproteins, lipids, hormones and bilirubin

is a retinal binding protein , transports vitamin A

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13
Q

what does a deficiency in vitamin A cause

A

visual impairment

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14
Q

name two beta globulins and their functions

A

transferrin- transports Fe3+, indicator of iron deficiency

fibrinogen- inactive form of fibrin, clotting of blood

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15
Q

what is the most abundant plasma protein

A

albumin

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16
Q

what stimulates the production of albumin

A

insulin and nutrient intake

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17
Q

when are albumin levels low

A

liver disease or starvation

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18
Q

what is albumins affinity and capacity for hydrophobic molecules

A

low affinity but high capacity

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19
Q

what endogenous lipophilic substances does albumin transport

A

fatty acids, bilirubin, thyroid hormone

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20
Q

what exogenous substances does albumin transport

A

drugs with weak hydrophobic capacity e.g. aspirin

21
Q

where is iron stored

A

in cells bound to ferritin

22
Q

why is iron important

A

component of haemoglobin, myoglobin, cytochromes

23
Q

what in the blood transports copper

A

ceruloplasmin

24
Q

what does a deficiency in ceruloplasmin result in

A

wilsons disease

25
Q

what are steroid hormones derived from

A

cholesterol

26
Q

which steroid hormones are hydrophobic

A

T3/4

27
Q

how are steroid hormones transported in the circulation

A

via transport molecules

  • thyroxine bound to thyroid-binding globulin
  • cortisol bound to cortisol-binding globulin
28
Q

why are transport molecules essential for steroid hormones

A

as would be eliminated by liver or kidney without them

29
Q

describe the structure of a lipoprotein

A

core of hydrophobic lipids (cholesterol esters, triglycerides)

surrounded by a shell of polar lipids (phospholipids) and apoproteins

30
Q

what is the role of lipoproteins

A

fat and cholesterol transport between organs and tissues

31
Q

what is the function oh HDL

A

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)

32
Q

what is the only organ capable of metabolising and excreting cholesterol

A

the liver

33
Q

what vitamins does the liver store

A

A, D and B12

34
Q

where does iron stored in the liver come from

A

haemoglobin

35
Q

what does cholesterol do to cell membranes

A

increases rigidity- good thing

36
Q

what is cholesterol pre cursors of

A

bile acids, steroid hormones, vit D

37
Q

is cholesterol soluble in water

A

no- especially if esterified to a long chain fatty acid

38
Q

how is cholesterol solubilised

A

via incorporation into lipoproteins- located in core of molecule

39
Q

where is the main site of cholesterol synthesis

A

liver

40
Q

what does HMG-CoA reductase

A

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

41
Q

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

A

increased by fasting

decreased by dietary cholesterol

also controlled by hormones

42
Q

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

A

regulation of calcium and phosphorus metabolism

43
Q

what steroid hormones are made from cholesterol

A

corticosteroids
androgens
astrogens

44
Q

what organ makes each steroid hormones from cholesterol

A

corticosteroids- adrenal cortex

androgens- testis

estrogens- ovary

45
Q

what is the main metabolic product from cholesterol

A

bile salts

46
Q

where are bile salts synthesised and secreted from

A

the liver

47
Q

where are bile salts stored

A

in gall bladder as component of bile

48
Q

how are bile salts recycled

A

by the enterohepatic circulation

49
Q

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

A

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

GI (64 decks)

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