Lecture 4- Transport of lipids Flashcards

Question

particle diamter relationship to density

Answer 1

Particle diameter inversely proportional to density

Answer 2

Density obtained by flotation ultracentrifugation

Answer 3

chylomicrons and VLDL

Answer 4

4-6h after a meal

Answer 5

IDL LDL HDL

Answer 6

* Each class of lipoprotein particle has a particular complement of associated proteins * Six major classes (ABCDEH) * apoB (VLDL, IDL, LDL) and apoA1 (HDL) important

Answer 7

VLDL, IDL, LDL

Answer 8

Can be **integral**- passing through phospholipid bilayer **Peripheral** - resting on top

Answer 9

packaging water insoluble lipid

Answer 10

1. Co-factor for enzymes 2. Ligands for cell surface receptors

Answer 11

transport of dietary TAG from the intestine to tissues such as adipose

Answer 12

transport of TAG synthesised in liver to adipose tissue for storage

Answer 13

short-liver precursor of LDL transport of cholesterol synthesied in the liver to the tissues

Answer 14

transport of cholesterol synthesised in liver to tissue

Answer 15

transport of excess choelsterol from cells to liver for disposal as bile salt and to cells requiring additional cholesterol

Answer 16

1. Loaded in the small intestine and **apoB-48** added before entering lymphatic system 2. Travel to the thoracic duct which empties into left subclavian vein and acquire 2 new apoproteins **(apoC and apoE)** once in blood 3. **ApoC binds lipoprotein lipase (LPL) on capillary wall of adipocytes and muscle** * Release of fatty acids into muscle and adipocytes depletes chylomicron of fat content 4. When TAG is reduced to 20%, **apoC dissociate and chylomicron becomes a chylomicron remnant** 5. Chylomicron remnants returns to the liver 6. **LDL receptor on hepatocytes bind apoE** and chylomicron remnant taken up by **receptor mediated endocytosis** 7. Lysosomal degradation of remaining contents for use in metabolism

Answer 17

VLDL made in liver for purpose of transporting TAG to other tissues 1. Apolipoprotein apob100 added during formation and apoC and apoE added from HDL particles in blood 2. VLDL binds to lipoprotein lipase (LPL) on endothelial cells in muscle and adipose and becomes depleted of TAG 3. In muscle…. Released fatty acids taken up and used for energy production 4. In adipose…. Fatty acids are used for the re-synthesis of TAG and stored as fat

Answer 18

VLDL --\> IDL --\> LDL 1. As triacylglycerol content of VLDL particles drops some, VLDL particles dissociates from the LPL enzyme complex and return to liver 2. If VLDL content depletes to ~30%, the particle becomes a short-lived IDL particle. 3. IDL particles can also be taken up by liver or rebind to LPL enzyme to further deplete in TAG content 4. Upon depletion to ~ 10%, IDL loses apoC & apoE and becomes an LDL particle (high cholesterol content)

Answer 19

1. Provides cholesterol from liver to peripheral tissue 2. Peripheral cells express LDL receptors and take up LDL via process of receptor mediated endocytosis

Answer 20

apoC or apoE **not efficiently cleared by the liver (liver LDL- receptor has a high affinity of apoE)**

Answer 21

Raised serum LDL associated with atherosclerosis

Answer 22

LDL has a much longe half life than VLDL or IDL

Answer 23

1. LDL has much longer half-life than VLDL or IDL making LDL more susceptible to oxidative damage 2. Oxidative LDL taken up by macrophages that can transform to foam cell and contribute to formation of atherosclerotic plaques

Answer 24

1. Oxidised LDL (longer half life more vulnerable to ROS) 2. Recognised and engulfed by macrophages 3. Lipid laden macrophages à foam cells accumulate in intima of blood vessel walls to form a fatty streak 4. Fatty streak evolves into atherosclerotic plaque 5. Growth and encroaches on lumen of the artery

Answer 25

1. Angina (narrowing of arteries) or.. 2. Rupture

Answer 26

* acute thrombosis (clot) by activating platelets and clotting cascade * Stroke * Myocardial infarction

Answer 27

* Xanthelasma * Tendon xanthoma * Corneal arcus

Answer 28

– yellow patches on eyelids

Answer 29

nodules on tendon

Answer 30

obvious white circle around eye (common in older people)

Answer 31

1. Cells requiring cholesterol express LDL receptors on plasma membrane 2. apoB-100 on LDL acts as a ligand for these receptors 3. Receptor/LDL complex taken into cell by endocytosis into endosomes 4. fuse with lysosomes for digestion to release cholesterol and fatty acids 5. LDL-R expression controlled by cholesterol conc in the cell

Answer 32

* Synthesis- nascent HDL synthesised by liver and intestine (low TAG levels) * HDL particles can also but off from chylomicrons and VLDL as they are digested by LPL * Free apoA-I can also acquire cholesterol and phospholipid from other lipoproteins and cell membranes to form nascent-like HDL

Answer 33

Nascent HDL accumulates phospholipids and cholesterol from cells lining blood vessels Hollow core progressively fills and particle takes more globular shape Transfer of lipids to HDL does not require enzyme activity

Answer 34

reverse cholesterol transport

Answer 35

1. HDL have ability to remove cholesterol from cholesterol-laden cells and return it to the liver 2. Important process for blood vessels as it reduced likelihood of foam cells and atherosclerotic plaque formation 3. **ABCA1 protein** within cell facilitates transfer of cholesterol to HDL 4. Cholesterol converted to cholesterol ester by lCAT

Answer 36

* Taken up by liver via specific receptors * Cells requiring additional cholesterol e.g. for steroid hormone synthesis can also utile scavenger receptors (SR-B1) to obtain cholesterol from HDL * HDL can also exchange cholesterol ester for TAG and VLDL via action of cholesterol exchange transfer protein (CETP)