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2 MEH > 4 Lipid Transport > Flashcards

4 Lipid Transport Flashcards

1
Q

What are Hyperlipoproteinaemias?

A

Raised plasma levels of 1+ lipoprotein classes

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2
Q

What (in general terms) causes hyperproteinaemias?

A

Defects in: Enzymes, receptors, apoproteins

Under removal/over production

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3
Q

Specifically, what causes each type of hyperlipoproteinaemia? (6)

A
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4
Q

What is hyper cholesterolaemia?

A

High cholesterol levels in blood–>cholesterol depostions in areas of body

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5
Q

What are some of the symptoms of hypercholesterolaemia? (3)

A
  1. Xanthelasm: yellow patches on eyelids
  2. Tendon xanthoma: nodule on tendon
  3. Corneal Arcus: white circle around eye
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6
Q

What is the first line of treatment for hyperlipoproteinaemias?

A

LIFESTYLE MODIFICATION

  1. Diet
    1. Reduce cholesterol, saturated lipids
    2. Increase fibre–> sequester bile salts
  2. Increase exercise
  3. Stop smoking
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7
Q

What drugs are used to treat hyperlipoproteinaemias if lifestyle modifications dont work?

A
  • Statins (Atorvastatin)
      • reduce cholesterol synthesis
    • inhibit HMG-CoA reductase
  • Bile Salt sequestrants (Colestipol)
    • _​_bind bile salts in GI tract
    • liver forced to produce more bile acids- uses up cholesterol
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8
Q

How does benecol reduce cholesterol levels?

A

Contains a molecule which bind preferentially to cholesterol

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9
Q

What are the ideal cholesterol plasma levels?

A

Total: 5mmol/L or less

If total cholestrol: HDL-cholesterol ratio is >6 then= high risk

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10
Q

Which vitamins are classed as lipids?

A

Vitamins A, D, E, K

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11
Q

In what form are the majority (98%) of lipids transported in the blood?

A

Lipoprotein particles

Phospholipid, cholesterol, cholesterol esters, proteins and TAG (triacylglycerol)

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12
Q

Apart from in the form of lipoprotein particles, how else can lipids be transported in the body (2%)?

A

Bound to albumin

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13
Q

Describe the structure of a phospholipid. (which part is hydrophobic and which part is hydrophilic)

A
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14
Q

How is cholesterol obtains for use in the body? (2)

A
  • Synthesised by Liver (most)
  • Diet
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15
Q

Give 3 functions of cholesterol in the body.

A
  • Modulate fluidity
  • Precursor for steroid hormones
    • Cortisol, aldosterone, testosterone, oestrogen
  • Prescursor for bile acid
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16
Q

In what form is cholesterol transported in the body?

A

Cholesterol ester

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17
Q

This image shows the structure of a lipoprotein. Label each of the arrows:

A
18
Q

One of the 5 classes of Lipoproteins is HDL (high density lipoproteins). What are the other 4?

A
  1. Chylomicrons
  2. VLDL
  3. IDL
  4. LDL
  5. (HDL)
19
Q

Out of the 5 classes of lipoproteins (Chylomicrons, VLDL, IDL, LDL, HDL) which ones are:

  • The main carriers of fat
  • The main carriers of cholesterol esters
A
20
Q

What method do we use to measure the density of lipoproteins in blood plasma?

A

Flotation ultracentrifugation

21
Q

Apoliproteins complement lipoproteins and can be integral or peripheral. What are the 6 major classes of Apoliproteins?

(Think simple)

A
  1. ApoA
  2. ApoB
  3. ApoC
  4. ApoD
  5. ApoE
  6. ApoH
22
Q

ApoB and ApoA are either (VLDL, IDL, LDL, HDL). Identify which type of Lipoprotein these apoliproteins can be.

A

apoB = VLDL, IDL, LDL

apoA = HDL

23
Q

Where in the body are chylomicrons loaded?

A

Small intestine

24
Q

Identify the apoliprotein which is added to th echylomicrons before they enter the lymphatic system.

A

apoB-48

25
Q

Fill in the missing gaps:

A chylomicron is formed in the ______ in the body. It then enters the ______ system. Once the chylomicron enters the left subclavian vein from the _____ duct, it acquires apo_ and apo_. apo_ binds to ________ _______ (which is found on adipocytes and muscle) , which allows fatty acids to be released from chylomicrons and enter cells.

A

Fill in the missing gaps:

A chylomicron is formed in the small intestine in the body. It then enters the lymphatic system. Once the chylomicron enters the left subclavian vein from the thoracic duct, it acquires apoC and apoE. apoC binds to lipoprotein lipase (which is found on adipocytes and muscle) , which then allows fatty acids to be released from chylomicrons and enter cells.

26
Q

Which organ in the body are chylomicron remnants returned to?

A

Liver

27
Q

Fill in the gaps:

Once the chylomicron remnants return to the liver, they have now become ___. There are ___ receptors on hepatocytes which allow for receptor mediated ______. Lysosomes release their contents.

A

Once the chylomicron remnants return to the liver, they have now become LDLs. There are LDL receptors on hepatocytes which allow for receptor mediated endocytosis. Lysosomes release their contents.

28
Q

What is the function of VLDL made in the liver?

A

Transporting TAG to other tissues

29
Q

What is the name of the enzyme that VLDLs bind to on endothelial cells in muscle and adipose to become depleted of TAG?

A

Lipoprotein lipase

30
Q

What is the main function of LDLs?

A

Provide cholesterol from the liver

(IDL= short lived)

31
Q

Why are LDLs not efficiently cleared by the liver?

Hint: Lacking …….

A

apoC and apoE

32
Q

Why are LDLs more susceptible to oxidative damage than VLDLs and IDLs?

A

LDLs have much longer half life than VLDLs and IDLs

33
Q

What happens to oxidised LDLs?

A
  1. Taken up by macrophages
  2. Transformed into foam cells
  3. Contribute formation of atherosclerotic plaques
34
Q

apoB-100 can be found on LDLs. What is the function of this apoliprotein?

A

Functions as ligand

Binds to LDL receptor on cell requiring cholesterol

35
Q

How are HDLs synthesised? (3 ways)

A
  1. By liver and small intestine
  2. Bud off from chylomicrons & VLDLs when digested by LPL
  3. Free apoA-I can acquire cholesterol and phospholipid from other lipoproteins- form HDLs
36
Q

HDLs do not require enzyme activity to mature. How do they mature?

A
  1. Accumulate phospholipids and cholesterol…
  2. …from cells lining blood vessels…
  3. …hollow core- fills
37
Q

What is the main function of HDLs?

A
  1. Removes cholesterol from cholesterol laden cells
  2. –> returns it to liver
  3. Reduces foam cell and plaque formation in blood vessels
38
Q

Name the molecule which facilitates the transfer of cholesterol to a HDL.

A

ABCA1

(then cholesterol converted to cholesterol ester by LCAT)

39
Q

Which organ takes up the mature HDL?

A

Liver

40
Q

Describe the 2 ways in which HDLs can be used once taken up by the liver.

A
  1. Exchange cholesterol ester via CETP (cholesterol exchange transfer protein) for TAG with VLDL
  2. Cells requiring aditional cholesterol- use SR-B1 (scavenger receptor) to obtain cholesterol from HDL

2 MEH (18 decks)

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