Cholesterol

Question 1

Where are bile salts generated and stored

Answer 1

Made in liver and stored in gall bladder

Question 2

Orlistat

Answer 2

Inhibitor of gastric and pancreatic lipases
Reduces fat absorption by 30%
Almost all excreted by faecal route
Can cause abdominal pain urgency to defeccate and increased callus and steatorrhea

Question 3

Steatorrhea

Answer 3

Fatty stool. Lack of bile salts means majority of fat passes through

Question 4

Bile salts purpose

Answer 4

Digest fats and help absorb fat soluble vitamins

Question 5

Lipoprotein

Answer 5

Lipids are transported by lipoproteins

Question 6

Chylomicrons location and role

Answer 6

Found in intestine
Dietary fat transport

Question 7

Very low density lipoprotein location and functional

Answer 7

Liver
Endogenous fat transport

Question 8

Intermediate density lipoprotein location and role

Answer 8

VLDL
LDL precursor

Question 9

Low density lipoprotein location and function

Answer 9

IDL
Cholesterol transport

Question 10

High density lipoprotein location and role

Answer 10

Liver
Reverse cholesterol transport and takes lipid back to the liver to be broken down into bile salts

Question 11

Chylomicrons

Answer 11

Where triglycerides are incorporated
They acquire apoproteins from HDL following release into bloodstream
They transport triglycerides and cholesterol

Question 12

Apoproteins

Answer 12

A protein that combines with a prosthetic group to form a conjugated protein

Question 13

Lipoprotein lipase

Answer 13

Degrades circulating triglycerides
Located on capillary endothelial cells lining adipose heart and skeletal muscle

Question 14

Cholesterol

Answer 14

Large non polar steroidal structure.
Increased or decreases membrane stiffness depending on temperature and nature of membrane

Question 15

Sources of cholesterol

Answer 15

Dietary intake limited to 500mg
Denovo synthesis-most if physiological requirements fulfilled through this
Deposition in adipose tissue

Question 16

Cholesterol biosynthesis steps

Answer 16

1) synthesis of isopentynyl pyrophosphate
2) condensation of 6 molecules of isopentynyl pyrophosphate to make squalene
3) cyclisation and demethylation of squalene by monooxygenases to make cholesterol

Question 17

Steroid hormone formation

Answer 17

Cholesterol makes pregnenolone making progestagens which split into glucocorticoid mineralcroticoid and androgens

Question 18

Vitamin d synthesis

Answer 18

Exposure of skin to sun needed
7-dehydrocholesterol in the presence of UV makes previtamin D3 which is converted to vitamin D3 which then makes calcitriol

Question 19

2 bile salts

Answer 19

Glycocholate and taurocholate

Question 20

Hypercholesterolaemia

Answer 20

Due to elevated LDL levels
Mono genic autosomal dominant
Patients within homozygous FH had a serum LDL 5 times more than normal, premature ASCVD,xanthomas
Patients with heterozygous FH have less severely elevated LDL ~2/3 times greater

Question 21

Pathogenesis

Answer 21

Mutations in LDL-R gene result in Poor LDL uptake into peripheral tissues

Question 22

How do statins inhibit cholesterol

Answer 22

As it is a competitive inhibitor of HMG-CoA reductase
This prevents conversion of HMG-CoA to mevalonate thus reducing cholesterol