Hsf Final (Lipoproteins Final 3)

Front 1

Lipoprotein lipase

Back 1

an enzyme that hydrolyzes lipids in lipoproteins, such as those found in chylomicrons and very low-density lipoproteins (VLDL), into three free fatty acids and one monoacylglycerol molecule. It requires Apo-CII as a cofactor (apoCII is required for activation of LPL).

Lipoprotein lipase is specifically found in endothelial cells lining the capillaries.

Front 2

WHAT ACTIVATES LPL?

Back 2

Insulin is known to activate LPL in adipocytes and its placement in the capillary endothelium.

Front 3

What is the primary apoprotein responsible for activation of LCAT?

Back 3

ApoAI is the primary apoprotein responsible for activation of LCAT

Front 4

What apoproteins are synthesized in the intestine?

Back 4

apoAI and AIV

Front 5

Since apoB100 vs apoB48 are synthesized from the same gene, what differentiates them?

Back 5

mRNA editing

apoB48 is produced exclusively by the intestine as a result of tissue-specific expression of an mRNA-editing enzyme activity (editase).

a substitution of thymidine (T) for cytidine (C) at position 6666, which creates a premature stop codon (TAA) in place of a codon for glutamine (CAA) at residue 2153

apoB48 is 48% of apoB100 in size

Front 6

Result of eating fat in Regulation of Lipoprotein Synthesis

Back 6

Dietary fat:
induces chylomicron production by the intestine
induces production of VLDL by the liver

Front 7

Result of eating carbohydrates in Regulation of Lipoprotein Synthesis

Back 7

Dietary carbohydrates:
increase VLDL production by stimulating fatty acid synthesis and insulin release

Front 8

Result of eating cholesterol in Regulation of Lipoprotein Synthesis

Back 8

Dietary Cholesterol:
suppresses expression of LDL receptors ; important determinant of plasma LDL levels

Front 9

LDL Clearance

Back 9

40% of plasma LDL is cleared by the liver

70% of LDL clearance is mediated by LDL receptors

Front 10

LDL clearnace:
Internalization and degradation of LDL by cells cause........

Back 10

1) increased intracellular cholesterol (which suppresses HMGCoA reductase activity (the rate-limiting enzyme in cholesterol synthesis))
2) stimulates acyl CoA: cholesterol acyltransferase (ACAT) activity (the intracellular cholesterol-esterifying enzyme)
3) suppresses LDL receptor synthesis

Front 11

What is the most common cause of accelerated atherosclerosis?

Back 11

a deficiency of LDL receptors
(prolonged sequestration of lipoproteins next to smooth muscle and endothelial cells leads to oxidative damage of the lipoproteins)

Front 12

Fatty Acids are converted into molecules of Acetyl CoA in a process called?

Back 12

BETA OXIDATION

Front 13

Glycerol formed by lipolysis is absorbed by the liver and phosphorylated, oxidized to dihydroxyacetone phosphate, and then isomerized to.....?

Back 13

glyceraldehyde 3-phosphate

Front 14

What hormone is responsible for the breaking down of lipids molecules (not referring to chylomicron or VLDL molecules) in circulation?

Back 14

Hormone Sensitive Lipase

Front 15

Lipid synthesis from carb's occurs when citrate is........?

Back 15

transported out of mito matrix and converted to AcCoA carboxylase, then converted into malonyl CoA by AcCoA carboxylase, then eventually into FA by adding glycerol in Endo Reticulum and transported into circulation

Front 16

Key regulatory points of lipid synthesis are?

Back 16

Acetyl CoA and NADH

Front 17

To make fat, you also need to have carbohydrates, derived from.....?

Back 17

from a combination of pyruvate and oxaloacetate to form citrate. Remember, citrate is the source of AcCoA for fat synth.
(Note: if oxaloacetate is being used to make energy, it wont be available to build fat)

Front 18

After Meal Insulin:

Back 18

1. Inhibits Hormone-sensitive lipase (HSL)
2. Stimulates triglycerides synthesis; FFA+a-glycerol phosphate (inc. with insulin-induced glucose uptake)
3. Stimulates secretion of LPL
stimulates glycolysis (uses glucose for fuel)
4. stimulates glycogenesis (storage of glucose)
5. stimulates FA synthase and AcCoA carboxylase (increases FA synthesis from glucose)

Result: Storage of triglycerides

Front 19

During Fasting:

Back 19

1. Plasma glucose dec.
2. Insulin levels decline
3. Drop in insulin activates HSL
4. Triglycerides hydrolyzed in adipocytes

Front 20

Exogenous Lipid Transport

Back 20

absorbed by the small intestine; packaged into chylomicrons (large lipoprotein)

Front 21

Endogenous Lipid Transport

Back 21

1. Liver synthesizes lipids de novo
2. secreted into the blood as very low-density lipoproteins (VLDL)

Front 22

_____ and ______ are cleared by the liver, BUT 60% of LDL are cleared by _____________ ?

Back 22

IDL and LDL; extrahepatic tissues

Front 23

Reverse Cholesterol Transport

Back 23

excess cholesterol accumulates in cell membranes of extrahepatic tissues and is returned to the liver via high-density lipoproteins (HDL)

Front 24

HDL

Back 24

1) excess cholesterol can accumulate in the cell membranes of extrahepatic tissues and is returned to the liver via high-density lipoproteins (HDL)
2. HDL acquires unesterified (or free) cholesterol
3. lecithin-cholesterol acyltransferase (LCAT) forms cholesterol esters
(transferred from HDL to VLDL by cholesterol ester transfer protein (CETP))

Front 25

Hepatic cholesterol can be.....?

Back 25

1. excreted in bile as either bile acids or free cholesterol 2. undergoes reabsorption by the intestine or excretion in the stool
3. hepatic cholesterol can be secreted with new hepatic lipoproteins

Front 26

cholesterol, triglycerides, cholesterol esters, and phospholipids transported by ....?

Back 26

LIPOPROTEINS

Front 27

Apoproteins are either completely or partially exchangeable among lipoprotein except for which apoproteins?

Back 27

except apoB 100 and B48

Front 28

Apoproteins are either completely or partially exchangeable among surface phospholipids and cholesterol?

Back 28

completely transferable

Front 29

Apoproteins are either completely or partially exchangeable among cholesterol esters and triglycerides ?

Back 29

Partially transferable and need CETP (cholesterol ester transfer protein)

Front 30

Which has a greater buoyant density? chylomicrons and VLDL's or LDL and HDL's?

Back 30

LDL and HDL's (smaller lipoprotein particles)

Front 31

Chylomicrons

Back 31

1. most triglyceride-rich (80% is triglyceride) & least dense
2. nearly absent in the fasting state
3. ApoB48 is the major structural protein
4. secreted into intestinal lymph with apoAI and AIV but rapidly lose these in plasma and acquire apoE, CI, CII, and CIII

Front 32

Very Low-density Lipoproteins (VLDL)

Back 32

1. produced by the liver
2. During fasting, major carriers of plasma triglycerides
3. apoB100 as their major structural apoprotein
4. Circulating VLDL also may contain apoE, CI, CII, and CIII

Front 33

Intermediate-density lipoproteins (IDL)

Back 33

1. 50% of small VLDL are lipolytically converted to IDL
2. contain apoB100
3. enriched in cholesterol esters
4. ApoCs are also lost, whereas apoE is retained (ApoC depleted)

Front 34

Low-density lipoproteins (LDL)

Back 34

1. cholesterol-rich
2. account for 70% of the cholesterol in plasma
3. derived from lipolysis of VLDL
4. deliver cholesterol to the artery wall
5. high level of plasma LDL or apoB100 is the best single predictor of increased risk for atherosclerosis
6. oxidation of LDL contributes to atherosclerosis.

Front 35

Lipoprotein (a) or Lp(a)

Back 35

LDL particle + Apo (a)
1. (Kringles)
2. Lp(a) level of >40 mg/dl is an independent predictor of coronary artery disease in Caucasians
3. May promote atherosclerosis by competing for plasminogen activation and subsequent lysis of fibrin clots
4. impairs receptor-mediated catabolism of the LDL

Front 36

High-density lipoproteins (HDL)

Back 36

1. associated with several minor apoproteins and enzymes, including LCAT, CETP, and a phospholipid transfer protein (enzymes involved in reverse cholesterol transport)
2. role in removal of cholesterol from the artery wall
3. high level of HDL cholesterol (or apoAI, the major apoprotein in HDL) is an
important predictor of decreased risk for atherosclerosis.

Front 37

Cholesterol esterification catalyzed by ........ a9enzyme) ?

Back 37

lecithin-cholesterol acyltransferase (LCAT)

Front 38

__________ is the most abundant protein in the α-lipoproteins (HDL), followed by __________

Back 38

ApoAI, apoAII

Front 39

_________ is virtually the sole protein in β-lipoproteins (LDL)

Back 39

ApoB100

Front 40

What apoprotein that has three common isoforms, directly affect plasma cholesterol levels?

Back 40

apoE

Front 41

Where are 3/4 of the apoproteins synthesized? The other 1/4th?

Back 41

liver, intestine