Lipoproteins

Question 1

Cholesterol is stored in the _ (organ) as _ (name) by _(enzyme)

Answer 1

a. Liver
b. Cholesteryl-ester (ester form is more fat soluble)
c. LCAT

Question 2

ampiphatic meaning. & e.g

Answer 2

molecule that is hydrophilic & hydrophobic

e.g. phospholipid

Question 3

The name of cholesterol transporters. & the types from biggest to smallest (& dec. fat; inc. protein & inc density)

Answer 3

lipoprotiens

1. chylomicrons
2. VLDL
3. IDL
4. LDL
5. HDL

Question 4

what’s the apoprotein (apo) of HDL & receptor which helps cells recognise HDL

Answer 4

1. Apo-A1

2. ABCA1

Question 5

How can cholesterol transfer from lipoprotein to cell (which needs it)?

Answer 5

When apoprotein (apo) on lipoprotein matches w/ a receptor on cell

Question 6

what’s the apoprotein (apo) of LDL

Answer 6

Apo-B-100

Question 7

4 ways cholesterol is used in the body

Answer 7

• Component of cell and organelle membranes
• Precursor for steroid hormones
• Precursor for vitamin D
• Precursor for synthesis of bile acids and salts

Question 8

_ occupies most of the volume of adipocytes.

Answer 8

Cholesterol

Question 9

where can cholesterol be found

Answer 9

inside, outside & within body

Question 10

The outer layer of the cell membrane contains (a), which is fat soluble and it is transported through the blood in the form of water-soluble carrier molecules using (b) as carriers

Answer 10

a. Cholesterol

b. Lipoproteins

Question 11

Lipoproteins consist of:

Answer 11

• Cholesterol
• Phospholipids
• Proteins
• Triglyceride

Question 12

functions of apolipoproteins

Answer 12

• mediate binding of lipoproteins w/ lipoprotein receptors
• required for synthesis of lipoproteins
• Co-factors for enzymes
• synthesis, secretion & catabolism of lipoproteins

Question 13

LDL vs HDL: what they do

Answer 13

• LDL: distributes cholesterol from liver to peripheral tissues
• HDL: takes cholesterol from peripheral tissues to liver

Question 14

what is LPL & function of LPL (lipoprotein lipase)

Answer 14

a) glycoprotein present on all cells
b) - breakdown TG (-> then carried by apo/lipoprotein)
- excess LPL > protects body from obesity
- deficiency LPL > bad = accumulation of chylomicron-TG in plasma

Question 15

describe LPLD

Answer 15

• LPL deficiency => elevates fat in blood
• rare genetic cond.
• Glybera: 1st gene therapy > remedy for LPLD

Question 16

affect of insulin on adipocytes & skeletal muscles in relation to LPL

Answer 16

• adipocytes activated to produce & secrete LPL

- skeletal muscle inhibit secretion of LPL

Question 17

which carrier carries ~ 2/3 of Cholesterol in plasma

Answer 17

LDL

Question 18

How is cholesterol in LDL taken up by the liver (hepatocytes)? & affect of excess LDL

Answer 18

1. LDL binds to LDL receptor on hepatocyte
2. LDL endocytosed by clathrin
3. LDL hydrolysed to AA, FA & cholesterol
4. cholesterol converted into chosteryl ester via LCAT
5. LDL receptor can go back to cell surface
   * NOTE: excess LDL could inhibit LDL receptor

Question 19

How does cholesterol bind to HDL form HDLc

Answer 19

1. cAMP activates Protein kinase A
2. phosphorylation => conformatioinal change => ATP can bind
3. opens channel => cholesterol can bind to HDL

Question 20

Function of Statin or HMG-CoA reductase inhibitors

Answer 20

cholesterol lowering drugs that inhibit the enzyme HMG-CoA reductase - produce cholesterol
=> low cholesterol = prevent CVD

Question 21

limitations to Friedewald equation

Answer 21

• chylomicrons present
• TG > 400 mg/dL (4.52mM)
• patients w/ type III hyperlipoproteinemia

Question 22

atherogenic cholesterols

Answer 22

• LDL & VLDL & IDL

all except HDL

Question 23

The equation used for calculation of non-HDLc =

Answer 23

non-HDLc = Tc - HDLc

Question 24

explain Tangier disease

Answer 24

• Hypolipoproteinemia / Hypolipidemia
• absence of the transporter ABCA1 transporter => accumulation of cholesterol in the cell = low cholesterol and HDL in serum.

Question 25

Describe the condition: familial hypercholesterolaemia

Answer 25

- primary disorder of lipoprotein metabolism (hyperlipidaemia) - Inc. LDLc in blood - *defects in LDL receptor (bc mutations) = not absorb LDL - OR excess production of LDL - OR ApoB100 is faulty

Question 26

Describe the condition: Hyperlipidemia (hyperprotenemia)

Answer 26

- Inc. TG OR Inc. Chol. | - elevated lipoproteins OR lipids (Both = combined/familial hyperlipidemia/Hyperlipoproteinemia)

Question 27

Describe the reverse indirect pathway which is mediated by _ & function

Answer 27

a. cholesteryl ester transfer protein (CETP) > exchanges TG in VLDL for cholesteryl esters in HDL b. 1. VLDL processed to LDL => removed from circulation by LDL receptor pathway 2. TG in HDL degraded by hepatic lipase => small HDL particles => uptake of cholesterol from cells

Question 28

describe the exogenous cycle: chylomicron metabolism | (eating)

Answer 28

1. TG & chol. from broken-down food is absorbed in the small intestine 2. lipids are transported in chylomicron 3. LPL breaks down chylomicron to VLDL & FFA -> goes to muscles & adipocytes 4. VLDL goes to the liver

Question 29

Describe the endogenous lipid transport cycle (fasting)

Answer 29

1. liver produces VLDL 2. VLDL (carry TG, Chol.) is broken down by LPL from tiss. => remove FFA &TG (to muscle, adipocytes) 3. this reduces the size of VLDL -> IDL -> LDL

Question 30

describe hypertriglyceridaemia & cause

Answer 30

- inc. TG, VLDL (not LDL) | - bc deficiency of LPL or over production of VLDL

Question 31

Describe the reverse direct pathway when there is a lot of cholesterol in tissues (need to be excreted)

Answer 31

1. Cholesterol in tissue taken up by HDL 2. LCAT converts cholesterol to cholesteryl ester 3. liver uptakes cholesteryl ester in via SR-BI (reverse scavenger)