Cholesterol Flashcards
What are the two major food molecules and where do they produce acetyl co A?
Sugars and fats produce acetyl coA in the mitochondria
What are the 3 primary sources that fats are derived from
- The diet.
- De novo biosynthesis (liver).
- Storage depots in adipose.
Where are bile salts generated?
The liver
Where are bile salts stored?
The gallbladder
During digestion, where do bile salts pass from and into?
From the bile duct into the intestines
What do bile salts do and why is it important?
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.
What does a lack of bile salts result in?
Majority of fat passing through the gut undigested and unabsorbed resulting in steatorrhea (fatty stool).
What is Orlistat?
A weight loss drug
What enzymes does Orlistat inhibit?
Gastric and pancreatic lipases
By what percent does Orlistat inhibit fat absorption and how is this fat excreted?
up to 30%, and almost all of the fat is excreted through faeces
How long is orlistat affective at treating obesity for?
up to 2 years
What are the main side effects of Orlistat?
Abdominal pain, urgency to defecate, increased flatus and steatorrhea
What transports lipids in the plasma?
Lipoproteins
What are the 5 lipoproteins and where are their sources?
Chylomicrons (CM)- Intestines
Very low density lipoproteins (VLDL)- Liver
Intermediate density lipoproteins (IDL)- VLDL
Low density lipoproteins (LDL)- IDL
High density lipoproteins (HDL)- Liver
What is the role of chylomicrons?
Dietary fat transport
What is the role of VLDLs?
Endogenous fat transport
What is the role of IDLs?
LDL precursor
What is the role of LDLs?
Cholesterol transport
What is the role of HDLs?
Reverse cholesterol transport
What cell are digested dietary products absorbed by and where are they found?
Enterocytes that line the brush border of the small intestine.
What happens to fats before incorporation into CM?
Triglycerides are resynthesized under the control of several enzymes
How are CM transported and where?
Via the lymphatics and on into the bloodstream
What do CMs acquire following release into the bloodstream and where from?
Apoproteins from HDL
Where specifically do chylomicrons travel before entering the bloodstream?
From the lacteals of the intestine to the thoracic duct, to the left subclavian vein where they enter the bloodstream
Where is Lipoprotein lipase located?
Capillary endothelial cells lining tissues including adipose, heart and skeletal muscle
What happens to the fatty acids?
used in beta oxidation
What happens to the glycerol?
Returned to liver for use in gluconeogenesis
What type of molecule is cholesterol?
A steroid
What does cholesterol do to membranes and how?
Increases or decreases membrane stiffness, depending on temperature and nature of membrane.
What percentage of cholesterol in the body is found in cell membranes?
Over 90%
What is the dietary cholesterol uptake limit in humans?
0.5g/day
Name a precursor to cholesterol and how it is generated
Clarify how is it a precursor if it is generate from it
Pregnenolone is generated from cholesterol by the action of the enzyme desmolase
How many classes of steroid hormones come from pregnenolone?
All 5
What vitamin can be synthesised from cholesterol?
Vitamin D3
What is required to initiate reaction to produce vitamin D3 from cholesterol?
Exposure of skin to sunlight
What does vitamin D3 deficiency in childhood lead to?
Rickets
What problem do lipoproteins solve?
Transporting hydrophobic molecules in an aqueous environment
What does the phospholipid monolayer in a lipoprotein contain?
Cholesterol and apoproteins
What is contained in the core of a lipoprotein?
Cholesterol esters and triacylglycerols
Where are cholesterol esters synthesised, and where from?
In the plasma, from cholesterol and the acyl chain of phosphatidylcholine (lecithin)
What enzyme is the reaction for synthesis of cholesterol esters catalysed by?
Lecithin:cholesterol acyltransferase (LCAT).
