Lipid metabolism Flashcards
1
Q
What are lipids
A
- Water-insoluble (hydrophobic) organic molecules
- Fatty acids, triglycerides, phospholipids, steroids, glycolipids, cholesterol
2
Q
What is a fatty acid
A
long aliphatic chain which is either saturated or unsaturated
3
Q
Saturated fatty acid
A
No double bonds
4
Q
Unsaturated fatty acid
A
Double bonds
5
Q
What is choelsterol?
A
Steroid alcohol of animal tissues
6
Q
Function of cholesterol
A
Precursor of steroids, bile acid and vit D
7
Q
How are lipids broken down?
A
- Lipids broken down by lipases
- Pancreatic lipase hydrolyses dietary triglycerides into monoglycerides and free fatty acids = chemical digestion
- Pancreatic lipase is only enzyme in fat digestion
8
Q
Which chemical signals bile release
A
CCK
9
Q
Emulsification
A
- Bile is yellow because bilirubin is
- Bile contains salts, cholesterol, lecithin and bilirubin
- Doesn’t contain digestive enzymes - no chemical digestion
- Bile salts aid fat digestion through detergent action and facilitate fat absorption
- Emulsification: converting large molecules into smaller ones
- Amphipathic: lipid-soluble part and water-soluble part
- Lipid soluble part binds to fat globules and intestinal mixing movement break them into smaller droplets
- Negatively charged particles stop droplets from recoalescing
Bile salt forms micelles
10
Q
Why is emulsification good?
A
Increases SA for lipase
11
Q
What does pancreatic lipase do?
A
Removes free fatty acids from triglyceride and produces 2-monoglyceride and free fatty acids
12
Q
What does cholesterol-esterase do?
A
Produces cholesterol and fatty acids
13
Q
Absorption of lipids
A
- Hydrophilic surface facilitates transport of hydrophobic lipids
- Inside enterocytes resynthesis of triglyceride and cholesteryl esters takes place
- Packaged into chylomicrons which enter lymphatic vessels through exocytosis
- Chylomicrons follow lymphatic system to thoracic duct and are conveyed to subclavian vein and enter blood stream
14
Q
Transport of lipid
A
- Lipids, triglycerides and cholesterol are carried in blood associated with proteins (apolipoproteins or apoproteins) in form of lipoproteins
- LDL and HDL - amount of cholesterol present, measured indirectly
15
Q
Classification of lipids
A
- Chylomicron (CM)
- Very low density lipoprotein (VLDL)
- Intermediate density lipoprotein (IDL)
- Low density lipoprotein (LDL)
- High density lipoprotein (HDL)
- Bigger size = less tightening
