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Metabolism > session 5-lipid transport,hyperlipoprotein/cholesterolaemia,ROS, > Flashcards

session 5-lipid transport,hyperlipoprotein/cholesterolaemia,ROS, Flashcards

1
Q

what are 98% of lipids carried as? And what are 2% carried as?

A

lipoproteins 98%

bound to ALBUMIN 2% (fatty acids bound to albumin mostly originate from adipose tissue)

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2
Q

in what 3 ways do lipoproteins differ?

A
  • lipid being transported
  • its origin
  • destination
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3
Q

what are the protein parts of lipoproteins called and what is their function?

A
  • apolipoproteins..are amphipathic (contain both hydrophobic and philic) so can interact with both the lipid and water
  • activate enzymes
  • recognise cell surface receptor
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4
Q

a spherical lipoprotein particle has a surface coat (shell) and hydrophobic core. What does each section contain?

A
  • Surface coat=cholesterol, apoproteins and phospholipids

- core=triacylglycerol and cholesterol esters

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5
Q

what is the role of chylomicrons?

A

transport TAGS from intestine to other tissues-e.g. adipose for energy production

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6
Q

name 3 classes of lipids carried in blood

A

triacylglycerol, fatty acids, cholesterol

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7
Q

what does VLDL do?

A

transport TAGS that are synthesised in the liver to adipose tissue for storage

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8
Q

what is the role of LDL?

A

transport cholesterol from liver to tissues

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9
Q

what is the role of HDL?

A

transport excess cholesterol from tissue to liver for disposal as bile salts

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10
Q

what is the role of lipoprotein lipase?

A
  • removes TAGs from chylomicrons and VLDL’s

- hydrolyses TAG..releasing fatty acids (taken to tissues for respiration) and glycerol (taken to liver)

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11
Q

where is lipoprotein lipase found?

A

inner surface of capillaries

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12
Q

what increases the synthesis of the lipoprotein lipase enzyme?

A

insulin

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13
Q

what is the role of LCAT? (lecithin:cholesterolacyltransferase)

A
  • converts surface lipid to core lipid
  • converts cholesterol to cholesterol esters using fatty acid derived from lecithin
  • lack of LCAT causes unstable lipoproteins of abnormal structure and thus failure of lipid transport
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14
Q

how do cells communicate with apoproteins on LDL particles for cholesterol uptake?

A

synthesis LDL receptors for apoprotein to bind to

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15
Q

what are 2 main diseases associated with plasma lipoproteins?

A

coronary artery disease and atherosclerosis

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16
Q

what is familial hypercholesterolaemia?

A

condition where there may be an absence or deficiency of LDL receptors on tissues
caused by elevated levels of LDL within the blood plasma

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17
Q

what is another name for familial hypercholesterolaemia?

A

type 2a hyperlipoproteinaemia

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18
Q

give 2 ways in which hyperlipoproteinaemias may be treated?

A

dietary and lifestyle modifications and statins (reduced cholesterol synthesis in tissues)

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19
Q

how does the liver dispose of cholesterol?

A

-converts it to bile salts which are taken to the GI tract to be disposed as faeces

20
Q

how are reactive oxygen species formed?

A

some electrons from the electron transport chain in oxidative phosphorylation leak and bind to oxygen…forming super oxide radicals (O2-). These free radicals with an unpaired electron form reactive oxygen species

21
Q

what enzyme changes a super oxide radical into hydrogen peroxide and oxygen?

A

SOD (super oxide dismutase)

22
Q

H2O2 is itself a ROS. What enzyme breaks it down into O2 and H20?

A

catalase

23
Q

what is the fenton reaction?

A

using fe2+ ions to form hydroxide ions which are also ROS-damages membranes and cannot be eliminated with an enzymatic reaction

24
Q

what is the name of the process whereby neutrophils and monocytes (cells of the immune system) release ROS?

A

oxidative burst

25
Q

why do immune system cells release ROS and what enzyme do they use?

A
  • kill the cell but also surrounding bacteria and fungi

- NADPH oxidase

26
Q

how is the NO- radical formed?

A

arginine and enzyme nitric oxide synthase with conversion of NADPH and O2—>NADP+ and H2O

27
Q

what do nitric oxide and oxygen react together to form and what does this thing do?

A

forms free radical peroxynitrite which is involved in inflammation

28
Q

what 2 species also defend against ROS besides catalase and SOD

A

NADPH and GSH (glutathione)

29
Q

what enzyme allows NADPH–>NADP and GSSG (glutathione disulphide)–> GSH?

A

Glutathione reductase (GSH reductase)

30
Q

what enzyme allows H2O2 to become H2O whilst GSH becomes GSSG?

A

GSH peroxidase

31
Q

What is type 1 hyperlipoproteinaemia and what is it caused by?

A

Increase of chylomicrons in plasma

Caused by defective lipoprotein lipase

32
Q

GSH peroxidase requires which element to function?

A

Selenium

33
Q

Which 3 lipoproteins will you find apoB on?

A

VLDL,IDL,LDL

34
Q

Which lipoprotein will you find apoAI on?

A

HDL

35
Q

Complete the passage with the correct words:

  1. Chylomicrons acquire apoE and c in the…..
  2. ApoC binds…..on adipocytes and muscle, releasing fatty acids and depleting chylomicron of its fat content
  3. ApoC dissociates off chylomicron which becomes a…..
  4. This returns to liver where LDL receptor on hepatocyte binds ApoE and endocytosis occurs. ….. Release remaining contents for use in metabolism (note: VLDL mechanism is very similar)
A
  1. Left subclavian vein
  2. lipoprotein lipase
  3. Chylomicron remnant
  4. Lysosomes
36
Q

What happens to a lipoprotein as more TAG is removed?

A

-change from VLDL to IDL to LDL

37
Q

Why aren’t LDLs efficiently cleared from the liver?

A

Do not contain ApoC or ApoE and liver LDL receptor has high affinity for ApoE

38
Q

LDL has a long half life compared to VLDL or IDL.what is the relevance of this?

A
  • more susceptible to oxidative damage

- taken up my macrophages which can turn into foam cells leading to plaque build up

39
Q

Which apoprotein binds to LDL receptors on cells that need cholesterol?

A

ApoB-100

40
Q

What protein in a cell transfers cholesterol to HDL? It is then converted to cholesterol ester (to form central part of lipoprotein for good structure) using….

A

ABCA1

LCAT

41
Q

Cells requiring additional cholesterol can use…..receptor to obtain cholesterol from HDL

A

Scavenger

42
Q

HDL can exchange cholesterol for TAG with VLDL via action of….

A

CETP…cholesterol exchange transfer protein

43
Q

Both chylomicrons and VLDL transport TAG. What is the difference between the TAG they each carry?

A

Chylomicrons-dietary TAG-that’s why they are found in small intestine
VLDL-tag synthesised in liver

44
Q

Which type of hyperlipoproteinaemia is caused by a defect of apoprotein E?

A

Type 3

45
Q

Give 3 clinical signs of hypercholesterolaemia (type 2 hyperlipoproteinaemia) and describe them.

A

Xanthelasma-yellow patches on eyes
Tendon xanthoma-nodules on tendon
Corneal Arcus-White ring in iris

46
Q

An atherosclerotic plaque can rupture, triggering thrombosis and blood clotting cascade. What 2 things does this lead to?

A

MI or stroke

Metabolism (14 decks)

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