Lecture 6: Lipids, Metabolism, Disorders and Analysis Flashcards
What are lipid fractions?
- Cholesterol
- Fatty acids
- Triglycerides
- Phospholipids
- Other lipid soluble substances (fat-soluble vitamins and steroid hormones, etc. (much smaller amount)
What is cholesterol?
A vital lipid in the body used for making cell membranes, tissues, steroid hormones, bile acid, vitamin D. Can be made exogenously or endogenously.
Where and how is cholesterol made?
Made in the liver from acetyl-CoA.
The reaction HMG-CoA synthase (3-hydroxy-3-methylglutaryl-CoA synthase) produces HMG-CoA from acetyl-CoA, before HMG-CoA is converted into mevalonic acid by HMG-CoA reductase, which goes on to become cholesterol.
How is cholesterol transported?
Transported as lipoproteins:
-LDL
-HDL
-IDL
What function does cholesterol play in membranes?
It is present in cell membranes to maintain the fluidity, compressibility, water penetration, and intrinsic curvature.
What are triglycerides?
Fats in the body that are stored forms of fatty acids, present in many cells in the body but especially in adipose. Held together by a glycerol molecule with 3 ester bonds holding 3 fatty acid chains.
Triglycerides that contain both saturated and unsaturated fatty acids are vital for cell membranes.
Triglycerides are transported as lipoproteins (VLDL and chylomicrons).
Free fatty acids are transported in plasma bound to albumin.
What are fatty acids?
Long carbohydrate chains with a carboxylic acid group on one end.
Can have C=C bonds in the chain (unsaturated), or only C-C bonds (saturated). Can be short, medium, or long chain.
Where are certain types of fatty acids obtained from in the diet?
Saturated - Animal sources
Unsaturated - Plant sources
An exception is omega-3 fatty acids from fish
What are phospholipids?
Similar to triglycerides, with a glycerol molecules bonded to 2 fatty acid chains with the final bond being to a phosphate group bonded to a choline molecule.
What are lipoproteins?
Lipids are not soluble, and therefore must be transported by something in plasma. Free fatty acids bind to albumin. And other lipids circulate as lipoproteins.
The structure consists of a single phospholipid layer (with some cholesterol) emulsifying a collection of triglycerides and cholesterol esters, Apolipoproteins are present in phospholipid layer. This creates a polar shell and non-polar core.
What types of lipoproteins are there?
Chylomicrons
VLDL -Very low density lipoprotein
IDL -Intermediate density lipoprotein
LDL -Low density lipoproteins
HDL -High density lipoproteins
From order of least dense to most.
What are chylomicrons?
- The largest and most buoyant lipoprotein.
- Formed in the intestine and are a transport vehicle for dietary fat.
- Triglyceride rich
- Exogenous pathway
What are VLDLs?
- Second largest lipoprotein
- Largest lipoprotein that contains endogenous lipid
- Triglycerides are endogenous
- Triglyceride rich
What are IDLs?
- Intermediate composition of lipids
- Carries endogenous lipids
- Produced as an intermediate between VLDL and LDL
- Core contains cholesterol ester and triglycerides.
What are LDLs?
- The main cholesterol containing lipoprotein
- End product of VLDL catabolism
- Mostly cholesterol esters in core
- Has apolipoprotein B100 embedded in phospholipid monolayer, as well as embedding itself in the core.
- “bad cholesterol”
- Endogenous pathway
