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Biochemistry Block 2 > Cholesterol (Deev) > Flashcards

Cholesterol (Deev) Flashcards

1
Q

What is one major function of cholesterol?

A

precursor for steroid hormones.

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2
Q

Organic compound with four fused rings arranged in a specific ABCD configuration.

A

Steroids

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3
Q

A subgroup of steroids with a hydroxyl group at the 3 position of the A-ring.

A

hydroxyl

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4
Q

Highly hydrophobic compound, and is the major sterol in animal tissues.

A

Cholesterol

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5
Q

Most important functions of Cholesterol:

A

structural component
maintain integrity and fluidity
enables cells to dispense within the cell
lipid rafts

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6
Q

What 3 things are involved with lipid rafts?

A

sphingolipids
cholesterol
phospholipids??

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7
Q

Cholesterol is a precursor for synthesis of what 3 things:

A

Bile salts
Steroid hormones
Vitamin D

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8
Q

Free cholesterol (unesterified) is found in ________ of all animal cells

A

membranes

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9
Q

_________ cholesterol (plasma cholesterol) is not found in membranes, bound to a protein that can solubilize them and transport them for the body.

A

Esterified

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10
Q

True False: Most cells can synthesize cholesterol

A

True

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11
Q

________ is the central organ that controls the overall cholesterol homeostasis.

A

Liver

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12
Q

Sources of liver cholesterol:

A

De novo synthesis
Diet
Delivered via HDLs

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13
Q

What are the routes for cholesterol clearance from the liver to the rest of the body?

A

Secretion into VLDL/ LDL

Cholesterol is secreted as free cholesterol into bile and converted to bile acids/salts

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14
Q

Lipid depositions can lead to __________ over time and narrowing of blood vessels.

A

plaque formation

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15
Q

Narrowing of blood vessels is called _________.

A

Atherosclerosis

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16
Q

Atherosclerosis (narrowing of blood vessels) can cause

A

increased risk of cardio- cerebro- and peripheral vascular disease

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17
Q

Narrowing of blood vessels is called _________, a potentially life threatening disease.

A

Atherosclerosis

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18
Q

Atherosclerosis (narrowing of blood vessels) can cause

A

increased risk of cardio- cerebro- and peripheral vascular disease

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19
Q

What are the substrates for cholesterol synthesis?

A

Acetyl CoA- to build carbons of cholesterol
NADPH- reducing equivalents
ATP- as energy

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20
Q

Why do low fat diets not lower cholesterol?

A

Low fat diets usually have higher carbohydrates, so there is more glucose

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21
Q

What is the enzyme important for conversion of Acetyl CoA to HMG CoA:

A

HMG-CoA synthase
2 isoenzyme forms:
-cytosolic- used to make cholesterol
-mitochondrial- used to make ketone bodies

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22
Q

What is the enzyme that catalyzes the synthesis of mevalonate? Rate limiting key regulatory step. (WE HAVE TO KNOW THIS ENZYME)

A

HMG-CoA reductase

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23
Q

Statin drugs are a big group of compounds that are considered ___________ inhibitors (most prescribed drugs in US)

A

competitive

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24
Q

How many molecules of acetyl CoA are required to make one molecule of cholesterol?

A

18 Acetyl CoAs for 1 cholesterol

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25
Q

Can cholesterol be metabolized to CO2 like sugars and fats? Why?

A

No, no enzyme for reverse reaction.

26
Q

Where does synthesis of cholesterol take place?

A

Cytoplasm

27
Q

Regulation of HMG CoA reductase:

A

Regulation of levels of the enzyme protein product
Sterol independent covalent modifications- phosphorylation and dephosphorylation via AMPK
Hormonal regulation- insulin and thyroxine upregulate HMG CoA reductase, glucagon and glucocorticoids downregulate it.

28
Q

If levels of sterols suddenly drop then _______ transcription factor will bind in order to start producing the sterol ring.

A

SREBP

29
Q

Cholesterol ring structure cannot be metabolized to ________ and ______ in humans.

A

CO2 and H2O

30
Q

Cholesterol is secreted into _____ and excreted from the body.

A

Bile

31
Q

> 60% of Bile is made up of _____.

A

bile salts

32
Q

How does cholesterol, bile acids, and bile work together?

A

Bile acids are the precursor for the synthesis of bile salts, and are produced in liver cells from cholesterol.
Cholesterol–> Bile Acids–> Bile salts

33
Q

What is a watery mixture of organic and inorganic compounds produced by the liver to help with digestion of lipids in the small intestine?

A

Bile

34
Q

Cholelithiasis (gall stones ) are derived from ________.

A

Cholesterol

35
Q

Too little ________ or too much ________ causes gall stones.

A

Bile salts

Cholesterol

36
Q

Possible causes of gall stones leading to lower bile salts or high cholesterol.

A

Inefficient enterohepatic cycling

liver dysfunction

37
Q

Spherical macromolecular complexes of lipids and specific proteins (apolipoproteins)

A

Lipoproteins

38
Q

Lipoproteins function is to transport:

A

cholesterol, fats and fat-soluble compounds in the plasma.

39
Q

______ transports dietary lipids, produced in enterocytes.

A

Chylomicrons

40
Q

What is VLDL?

A

Very low density lipoproteins transport newly synthesized lipids produced in hepatocytes.

41
Q

What is LDL?

A

Low density Lipoproteins- transport cholesterol to peripheral tissues

42
Q

What is HDL?

A

High density lipoproteins. transport cholesterol from periphery to the liver.

43
Q

How are lipoproteins arranged?

A

One layer of phospholipids (PC and SM)

Hydrophilic head and hydrophobic fatty acid tails.

44
Q

There are 11 different types of ___________ _________.

A

Amphipathic apolipoproteins

45
Q

What are the largest, least dense, and highest fat percentage of all lipoproteins?

A

Chylomicrons

46
Q

What are smaller and more dense than chylomicrons and are produced in hepatocytes (liver cells) to distribute fat away from the liver to peripheral tissues.

A

VLDLs

47
Q

What makes up the highest percentage of cholesterol? These are the bad cholesterols.

A

LDLs

48
Q

This is the second highest percentage of cholesterol ~25% which brings peripheral cholesterol to the liver. Good cholesterol.

A

HDLs

49
Q

Size and density of ________ are routinely used in plasma lipid profiling, have to be in fasted patient to be accurate.

A

lipoproteins

50
Q

Which of the lipoproteins would you expect to vary based on recent meals?

A

Chylomicrons
VLDLs
because they are very shortly lived particles, degraded quickly.

51
Q

Chylomicrons go to the ______ (hospital) and _______ of intestinal mucosal cells, using _______ as scaffold protein.

A

ER
Golgi
Apo B48

52
Q

Lipids are transferred to ApoB-48 via a _______.

A

microsomal Transfer Protein (MTP)

53
Q

_________ is the central organ for lipoprotein pathways.

A

liver

54
Q

If there is excess free cholesterol:

A

converted to CE by ACAT (acyl CoA: cholesterol acyltransferase) and stored in lipid droplets

55
Q

_______ are very sensitive to oxidizing agents.

A

Lipids

56
Q

3 factors increasing propensity for producing modified LDL in the circulation:

A

High blood sugar
Oxidative stress
Chemicals in tobacco smoke

57
Q

HDL does reverse ______ transport.

A

Cholesterol, therefore HDL is good cholesterol

58
Q

This disease is deficiency of Apo CII or Lipoprotein lipase (LPL)

A

Type 1 hyperlipoproteinemia

59
Q

Disease that is a defect in LDL receptor

A

Type IIa hyperlipidemia

60
Q

Disease that is a defect in Apo E protein synthesis

A

Type III hyperlipoproteinemia

61
Q

This disease is a defect in the microsomal transfer protein (MTP)…
Progressive degeneration of the retina that can progress to near-blindness (due to dificiency of Vitamin A, retinol)

A

Abetalipoproteinemia (Bassen Kornzweig syndrome)

Biochemistry Block 2 (13 decks)

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