Biochemistry week 4

Question 1

What do lipoproteins transport

Answer 1

• Lipids in blood

Question 2

Explain the structure of lipoproteins

Answer 2

• Spherical with a neutral lipid core and Amphipathic shell

Question 3

Where is apoliproteins synthesised

Answer 3

Liver and small intestine

Question 4

Name 2 characteristics of chylomicrons

Answer 4

• Low density and large in size

Question 5

Where are chylomicrons formed

Answer 5

• In the intestinal mucosa

Question 6

What do chylomicrons carry

Answer 6

Exogenous lipids

Question 7

What does the assembly of chylomicrons involve

Answer 7

• MTP- Microsomal TAG transfer protein

Question 8

EXPLAIN the process of chylomicron Metabolism

Answer 8

-Nascent chylomicron Recieves apo E and CII from HDL
-APO CII activates lipoprotein lipase(LPL)
- LPL breaks down TAG into Fatty acids and glycerol
- CM ( chylomicron )remnant is taken up by liver via APO

Question 9

What does a deficiency of LPL OR apo CII lead to

Answer 9

Type 1 hyperlipoproteinemia

Question 10

Where is lipoprotein lipase found

Answer 10

On capillary walls of adipose , cardiac and skeletal muscle

Question 11

What is lipoprotein lipase activated by + What is the synthesis stimulated by

Answer 11

• Actovated by apo C-II
  -Synthesis stimulated by iNSULIN

Question 12

Where does VLDLS originate from’’’’’
\’
“

Answer 12

Liver

Question 13

What does VLDLS Cary

Answer 13

Endogenous TAGs to peripheral tissues

Question 14

Explain how VLDL is converted to LDL

Answer 14

converted to IDL then converted to LDL via LPL action and CETP-mediated exchanges

Question 15

What does Fatty liver result from

Answer 15

VLDL secretion imbalance

Question 16

What does LDL stand for

Answer 16

Low density poproteins

Question 17

Where are LDLs( low density lipoproteins ) derived from

Answer 17

VLDL in the blood stream

Question 18

What are the 3 functions of LDLs

Answer 18

-Transport cholesterol from the liver to the peripheral tissues
- Facilitates membrane formation and steroid hormone synthesis
-Returns cholesterol to the liver

Question 19

Explain the difference between LDL and VLDL

Answer 19

LDL particles have less TAGs compared to VLDL

Question 20

Explain the process of LDL uptake + regulation

Answer 20

1. LDL receptors recognize apo B-100 and apo E.
2. Endocytosis of LDL-receptor complex.
   3.Vesicle loses clathrin → forms endosomes.
3. LDL separates from receptor.
4. Receptors are recycled; LDL is sent to lysosomes and degraded by lysosomal acid hydrolases → releases cholesterol, amino acids

Question 21

Explain al the regulation steps for LDL

Answer 21

-High cholesterol inhibits HMG- coA reductase , lowers cholesterol synthesis
-Low LDL receptor gene expression , leads to low LDL uptake

Question 22

What happens to the Oxidized LDL

Answer 22

• Macrophages uptake oxidized LDL via scavenger receptors( SR-A)

Question 23

What is HDL produced by

Answer 23

Mostly liver, a bit by intestines

Question 24

What is the main functiuons of HDL

Answer 24

• Carries cholestrol from peripheral tissues to the liver

Question 25

After cholestrol is carried to the liver by HDL what happens to it

Answer 25

- Either converte to biles acids or lipoproteins or excreted in bilw

Question 26

What does HDL contain

Answer 26

phospholipids and apoliporteins

Question 27

What is the structure of Nascent HDL + what does it contain

Answer 27

Disk shaped, contains mainly phospholipids and Apo A,C,E

Question 28

What does HDL act as a resrvoir for

Answer 28

- ApoE and Apo C11

Question 29

What does APOc11 AND ApoE activate

Answer 29

chylomicrons and VLDL

Question 30

What can HDL be seen as

Answer 30

Good cholesterol

Question 31

What is there an inverse realtionship with including HDL levles

Answer 31

Inverse relationship with HDL lebls and CHD

Question 32

What is High HDL linked to

Answer 32

low risk of coronary artery disease

Question 33

Explain the process of HDL metabolism

Answer 33

LCAT esterifies cholesterol → stored in HDL core ABCA1 transporter helps form HDL3 from free cholesterol HDL3 → HDL2 after esterification HDL2 taken up by SR-BI receptor in liver Cholesteryl ester transfer protein (CETP) moves esters to VLDL/LDL Phospholipid transfer protein (PLTP) helps transfer phospholipids between particles

Question 34

Name the 2 different types of HDL

Answer 34

-Nascent HDL -Mature HDL

Question 35

Explain the steps in plaque formation starting from Endothelial injury

Answer 35

1.Endothelial injury- caues monocytes to become macrophages 2.Macrophages engulf Oxidzed LDL and become FOAM CELLS 3. Foam cells accumulate, release cytokines, which attract smooth muscle cells + form plaque

Question 36

What cuases atherosclerosis

Answer 36

When cholesterol esters build up in foam cells