Cholestero-Lipoprotein-Steroid Metabolism Chp 18

Question 1

Cholesterol is considered to be what type of Compound?

Answer 1

Hydrophobic

Question 2

What does the structure of Cholesterol consist of?

Answer 2

-4 fused hydrocarbon rings (A-D) called the Steroid nucleus -has 8 carbon -branched hydrocarbon chain attached to carbon 17 of the D ring -Ring A has hydroxyl group at carbon 3 -Ring B has a double bond between carbon 5 and carbon 6

Question 3

Draw Structure of Cholesterol

Answer 3

Question 4

What produces even more of a hydrophobic Cholestery Ester

Question 5

T or F

Cholesterol is synthesized by virtually all human tissues

Question 6

Cholesterol is primarily synthesized primarily by what tissues

Question 7

What are all the Carbon Atoms in Cholesterol provided by

Question 8

What is cholesterol and what is it responsible for

Answer 8

• structural component of all cell membrances
• modulating their fluidity
• in specialized tissues cholesterol is a precursor of bile acids-steroid hormones and vitamin D

Question 9

What organ plays a central role in the regulation of the body’s cholesterol homeostasis

Question 10

What are Sterols

Answer 10

Steroids with 8 to 10 Carbon atoms in the side chain at carbon 17 and a hydroxyl group at carbon 3

Question 11

What does Cholesterol arise from

Question 12

What is the intestinal uptake of cholesterol mediated by

Question 13

In synthesis of cholesterol: all of the carbon atoms in chloesterol are provided by what

Question 14

In synthesis off cholesterol what provides the reducing equivalents

Question 15

The synthesis of cholesterol is considered to be what type of reaction ?

Answer 15

Endergonic= requires energy to be driven, are non-spontaneous and energy is gained

Question 16

What is the synthesis of cholesterol reaction driven by

Question 17

Synthesis of cholesterol requires Enzymes in both: what structures

Answer 17

The cytosol and membrane of the smooth endoplasmic reticulum

Question 18

First two reactions in the cholesterol synthetic pathway are similar to what

Answer 18

-Pathway that procuduces ketones bodies

Question 19

The first two reactions of cholesterol synthesis are similar to pathway of ketone bodie production: describe or draw the pathway of ketone prouduction

Answer 19

Attachment

Question 20

The first two acetyl CoA molecules condense to form what ?

Question 21

Third molecule of Acetyl CoA is added by what enzyme and what does it produce

Answer 21

HMG Co A synthase and produces HMG CoA (6 carbon compound)

Question 22

Liver parenchymal cells contain 2 info Enzymes of the sysnthase: what are they

Answer 22

1- Cytosolic enzyme- participates in cholesterol sysnthesis

2- Mitochondrial enzyme-functions in the pathway of ketone body synthesis

Question 23

Once 3-hydroxyl-3-methylglutaryl CoA (HMG CoA) has been produced–Synthesis of Mevalonate takes place:

It is the REDUCTION of (HMG CoA) to Mevalonate which is catalyze by what enzyme?

Answer 23

Catalized by enzyme -HMG CoA Reductase

Question 24

The reduction of HMG CoA by HMG CoA reductase is considered to be what type of reaction in cholesterol synthesis?

Answer 24

This reaction is considered to be a Rate Limiting & Key Regulatory Step

Question 25

In the sysntesis of Mevalonate: which occurs in Cytosol: how many molecules of reducing agent are used ?

And is this reaction considered irreversible?

Answer 25

2 molecules of NADPH are used as reducing agent and releases CoA, making the reaction irreversible.

Question 26

What is the integral membrane protein of the ER

Answer 26

HMG CoA reductase

Question 27

Verbalize process of Cholesterol synthesis:

Answer 27

1. Acetyl CoA are converted to 3-hydroxyl-3-methylglutaryl-CoA (HMG-CoA)
2. HMG-CoA is converted to Mevalonate
3. Mevalonate is converted to the isoprene based molecule - Isopentenyl Pyrophosphate (IPP)
4. IPP molecules are converted to Squalene
5. Squalene is converted to Cholesterol