Cholesterol

Question 1

What are the two major food molecules and where do they produce acetyl co A?

Answer 1

Sugars and fats produce acetyl coA in the mitochondria

Question 2

What are the 3 primary sources that fats are derived from

Answer 2

1. The diet.
2. De novo biosynthesis (liver).
3. Storage depots in adipose.

Question 3

Where are bile salts generated?

Answer 3

The liver

Question 4

Where are bile salts stored?

Answer 4

The gallbladder

Question 5

During digestion, where do bile salts pass from and into?

Answer 5

From the bile duct into the intestines

Question 6

What do bile salts do and why is it important?

Answer 6

They emulsify fats in the intestine, aiding digestion and absorption of fats and also of fat-soluble vitamins e.g. A, D, E and K.

Question 7

What does a lack of bile salts result in?

Answer 7

Majority of fat passing through the gut undigested and unabsorbed resulting in steatorrhea (fatty stool).

Question 8

What is Orlistat?

Answer 8

A weight loss drug

Question 9

What enzymes does Orlistat inhibit?

Answer 9

Gastric and pancreatic lipases

Question 10

By what percent does Orlistat inhibit fat absorption and how is this fat excreted?

Answer 10

up to 30%, and almost all of the fat is excreted through faeces

Question 11

How long is orlistat affective at treating obesity for?

Answer 11

up to 2 years

Question 12

What are the main side effects of Orlistat?

Answer 12

Abdominal pain, urgency to defecate, increased flatus and steatorrhea

Question 13

What transports lipids in the plasma?

Answer 13

Lipoproteins

Question 14

What are the 5 lipoproteins and where are their sources?

Answer 14

Chylomicrons (CM)- Intestines
Very low density lipoproteins (VLDL)- Liver
Intermediate density lipoproteins (IDL)- VLDL
Low density lipoproteins (LDL)- IDL
High density lipoproteins (HDL)- Liver

Question 15

What is the role of chylomicrons?

Answer 15

Dietary fat transport

Question 16

What is the role of VLDLs?

Answer 16

Endogenous fat transport

Question 17

What is the role of IDLs?

Answer 17

LDL precursor

Question 18

What is the role of LDLs?

Answer 18

Cholesterol transport

Question 19

What is the role of HDLs?

Answer 19

Reverse cholesterol transport

Question 20

What cell are digested dietary products absorbed by and where are they found?

Answer 20

Enterocytes that line the brush border of the small intestine.

Question 21

What happens to fats before incorporation into CM?

Answer 21

Triglycerides are resynthesized under the control of several enzymes

Question 22

How are CM transported and where?

Answer 22

Via the lymphatics and on into the bloodstream

Question 23

What do CMs acquire following release into the bloodstream and where from?

Answer 23

Apoproteins from HDL

Question 24

Where specifically do chylomicrons travel before entering the bloodstream?

Answer 24

From the lacteals of the intestine to the thoracic duct, to the left subclavian vein where they enter the bloodstream

Question 25

Where is Lipoprotein lipase located?

Answer 25

Capillary endothelial cells lining tissues including adipose, heart and skeletal muscle

Question 26

What happens to the fatty acids?

Answer 26

used in beta oxidation

Question 27

What happens to the glycerol?

Answer 27

Returned to liver for use in gluconeogenesis

Question 28

What type of molecule is cholesterol?

Answer 28

A steroid

Question 29

What does cholesterol do to membranes and how?

Answer 29

Increases or decreases membrane stiffness, depending on temperature and nature of membrane.

Question 30

What percentage of cholesterol in the body is found in cell membranes?

Answer 30

Over 90%

Question 31

What is the dietary cholesterol uptake limit in humans?

Answer 31

0.5g/day

Question 32

Name a precursor to cholesterol and how it is generated Clarify how is it a precursor if it is generate from it

Answer 32

**Pregnenolone** is generated from cholesterol by the action of the enzyme desmolase

Question 33

How many classes of steroid hormones come from pregnenolone?

Answer 33

All 5

Question 34

What vitamin can be synthesised from cholesterol?

Answer 34

Vitamin D3

Question 35

What is required to initiate reaction to produce vitamin D3 from cholesterol?

Answer 35

Exposure of skin to sunlight

Question 36

What does vitamin D3 deficiency in childhood lead to?

Answer 36

Rickets

Question 37

What problem do lipoproteins solve?

Answer 37

Transporting hydrophobic molecules in an aqueous environment

Question 38

What does the phospholipid monolayer in a lipoprotein contain?

Answer 38

Cholesterol and apoproteins

Question 39

What is contained in the core of a lipoprotein?

Answer 39

Cholesterol esters and triacylglycerols

Question 40

Where are cholesterol esters synthesised, and where from?

Answer 40

In the plasma, from cholesterol and the acyl chain of phosphatidylcholine (lecithin)

Question 41

What enzyme is the reaction for synthesis of cholesterol esters catalysed by?

Answer 41

Lecithin:cholesterol acyltransferase (LCAT).