Lipid

Question 1

whats the function of cholesterol?

Answer 1

1- structure of membranes

2- precursor of steroid hormones and bile acids

Question 2

where do you get most of the cholesterol ?

Answer 2

synthesized de novo

Question 3

how are lipids and cholesterol transported within the body?

Answer 3

lipoproteins

Question 4

whats the basic structure of cholesterol ?

Answer 4

4 rings

polar head pointing outside

Question 5

whats does the 4 rings do?

Answer 5

increase fluidity

Question 6

whats the function of polar head?

Answer 6

ester bond forming

Question 7

whats the form of cholesterol that is running in your body

Answer 7

cholesterol ester form ( 2 cholesterol bond by ester bond )

Question 8

whats the substrate of cholesterol ?

Answer 8

acetyl coa

Question 9

whats the cofactor that is used?

Answer 9

NADPH –> anabolic

Question 10

what are the steps in byiosynthesis of cholesterol?

Answer 10

2 acetyl coa —> HMG COA —-> mevalonate —>IPP —> squalene –> cholesterol

Question 11

whats the enzyme that is responsible for combining the 2 acetyl
coa

Answer 11

thiolase

Question 12

whats enzyme responsible for converting acetoacyle coa ( 2 acetyl coa ) to HMG COA

Answer 12

HMG COA synthase

Question 13

whats the enzyme responsible for converting HMG COA into mevalonate?

Answer 13

HMG COA REDUCTASE

Question 14

whats the main limiting STEP and the one regulating cholesterol synthesis?

Answer 14

HMG coa —-> mevalonate

by HMG REDUCTASE

Question 15

what cofactor does HMG coa reductase need?

Answer 15

NADPH

Question 16

whats the short regulation of HMG coa reductase?

Answer 16

phosphorylation of the enzyme :

if you add phosphate it will become inhibited and inactive

Question 17

whats the kinase that is responsible for the short term regulation?

Answer 17

AMP dependent protein kinase

its active in AMP ( low energy state ) and it will inhibit HMG COA reductase by phosphorylation it , because we dont have energy to produce cholesterol

Question 18

whats long term regulation of HMG COA ?

Answer 18

degradation and formation of the enzyme itself

Question 19

what could lead to degradation of HMG coa ?

Answer 19

cholesterol negative feedback

Question 20

whats the transmembrane in the HMG COA that is responsible for the degradation?

Answer 20

sterol sensing domain

Question 21

whats the enzyme responsible for forming ester bonds between cholesterol ?

Answer 21

ACAT ( intracelluar )

Question 22

whats the enzyme responsible for forming ester bonds between cholesterol EXTRACELLUAR ?

Answer 22

LCAT

Question 23

can we degrade cholesterol?

Answer 23

no

Question 24

whats the fate of cholesterol?

Answer 24

converted into bile acids and is secreted in bile

Question 25

whats lipoprotiens?

Answer 25

particles found in plasma that transport lipids including cholesterol

Question 26

what are the 5 examples of lipoproteins ?

Answer 26

Chylomicrons ( largest , lowest in density ) VLDL IDL LDL HDL ( smallest but highest in density ) AS YOU GO DOWN YOU LOSE TRIGLYERICDES

Question 27

which apo protein is found in lipoproteins made by intestine?

Answer 27

B48

Question 28

which apo protein is found in lipoproteins made by liver?

Answer 28

b100

Question 29

which lipoprotein has the highest compositon of triglycerides and lowest cholesterol?

Answer 29

chylomicrons

Question 30

which lipoprotein has the highest composition of cholesterol ?

Answer 30

LDL

Question 31

which lipoprotein has the highest protein composition ?

Answer 31

HDL

Question 32

which lipoprotein has apo protein b48

Answer 32

chylomicrons because its formed in the intestine

Question 33

which lipoprotein has apo protein b100

Answer 33

VLDL cuz its made in the liver IDL LDL

Question 34

under which circumstances you cant find chylomicros in plasma?

Answer 34

fasting for 12 hours after a meal

Question 35

describe the cycle of chylomicrons?

Answer 35

AFTER A MEAL 1- small intestine will collect both cholesterol and triglycerides and surrounds them with APPO PROTEIN B48 2- HDL gives the chylomicron APO C 2 AND APO E 3- chylomicrons travel in the blood until it reaches the liver 4- during the travel , LIPOPROTEIN LIPASE WILL BE ACTIVATED BY APO C WHICH WILL BREAD TRIGYLCERIDE FOR STORAGE 5- when it reaches the liver most of the triglycerides will be gone and only cholesterol will be there 6- before it enters the liver it will give HDL apo C2 BACK 7- Chylomicrons remimant will be reach the liver and it will be RECOGNIZED VIA APO E AND IT MEDIATES THE UPTAKE

Question 36

whats the function of apo c2?

Answer 36

activation of lipoprotein lipase and degradation of TRIglycerides

Question 37

whats the function of apo E?

Answer 37

its helps the liver uptake chylomicrons remnant

Question 38

describe the cycle of VLDL, IDL, LDL?

Answer 38

in the liver there will be 3 sources of cholesterol : one is from the chylomicrons coming with cholesterol only ( remember the triglycerides where taken by lipoprotein lipase ) one is from the de novo the liver synthesis cholesterol one is from adipose tissue so what does the liver do? it combines all of them and covers them with APO B 100 forming : VLDL 1- VLDL will leave the liver with only APO B 100 2- HDL will give VLDL apo c2 and apo E --> VLDL WILL HAVE APO B 100 + APO C2 + APO E 3- while VLDL travel in the blood stream , APO C2 will activate lipoprotein lipase and it will start degrading triglycerides like in the chylomicrons scenario 4- after losing bit of triglycerides it will become IDL 5- IDL ( apo b100 + Apo c2 + apo E) will give back APO C2 AND APO E back to the HDL 6- after giving back the apo proteins it will become LDL 7- LDL ( only have apo b 100) is mostly formed of cholesterol and it cant be degraded so it will have options either : GO BACK TO THE LIVER FOR HELP VIA LDL RECEPTOR DEPOSIT THE CHOLESTEROL IN ENDOTHELIUM AND CAUSE ATHEROSCLEROSIS

Question 39

whats the function of LDL receptor?

Answer 39

it will make the liver endocytose LDL

Question 40

what does the liver does when it has soo much cholesteorl?

Answer 40

1- Stops synthesis 2- LDL receptors endocytosis 3- Starts storing the already formed the cholesterol ( ACAT)

Question 41

Describe HDL?

Answer 41

its formed by the body to take the deposited cholesterol and free cholesterol from tissue back to the liver ( good thing )

Question 42

whats are other functions of HDL

Answer 42

- transfer cholesterol back to the liver - give proteins to the other lipoproteins -convert cholesterol to cholesterol ester via LCAT ( EXTRACEULLAR )

Question 43

how does HDL give other lipoproteins the apo proteins

Answer 43

CETP enzyme cholesterol ester transfer protein

Question 44

whats lipoprotein a?

Answer 44

LDL that has apo a that is bound to apo b100 disulfide linkage

Question 45

whats the function of lipoprotein A?

Answer 45

unknown

Question 46

whats risk associated with Lipoprotein A

Answer 46

premature coronary artery disease and stroke