Lipids
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Lipids are
heterogenous organic molecules that exist in a few different forms and have several purposes
Give 3 functions of lipids
• a stored form of energy • a structural component of cell membranes • needed as enzyme cofactors • used in hormones • used for the synthesis of Vitamins A, D, E and K • used as signalling molecules
What are the major lipid classes?
• fatty acids • triacylglycerides • phospholipids
What are fatty acids?
Hydrocarbon chains with a carboxylic group at one end • can be saturated or unsaturated • nomenclature defines which is which
What are the four types of fatty acids?
Essential fatty acids - must be obtained from plants Good fats - high in polyunsaturated fatty acids Bad fats - high in saturated fatty acids Really bad fats - trans fatty acids
Give an example of an essential fatty acid
• Linoleic acids - A-Linoleic acids
Give an example of a good fat
Plant oils e.g. sunflower oil
Give an example of a bad fat
Stearic acid
Give an example of a really bad fat
Margarine
Essential fatty acids must be obtained via
our diet, since humans cannot introduce double bonds beyond carbon nine
What are triacylglycerides?
Esters of fatty acids and glycerol - water insoluble • coalesce into droplets in water • major component of adipose tissue • act as insulation and dietary fuel
What are phospholipids?
Glycerol bonded to two fatty acids and a phosphate group • amphipathic • form basic structure of the cell membrane
What is the main dietary lipid?
Triglycerols
Where does most digestion of triglycerols take place? Through the use of what?
Small intestine pancreatic enzymes, emulsification by bile salts and peristalsis
Most triglycerols are digested by ___ into ___
pancreatic lipase monoacylglycerol and two fatty acids
Cholesterol esters are broken down to
cholesterol and a fatty acid
Phospholipids are hydrolysed to
a fatty acid and lysophospholipid
Mixed micelles release their contents when they
approach the brush border
The intestinal cells repackage ___ into ___ which are released ___
TAG, fatty acids and cholesterol esters chylomicrons into the blood via the lymphatic system
When lipids reach the tissues, TAG is hydrolysed to ___ by ___
fatty acids and glycerol lipoprotein lipase
The resulting free fatty acids are used for ___ or ___
energy re-esterified into TAG for storage
Free fatty acids are transported in lipoproteins in a complex with
serum albumin
Fats are also transported in
high and low density lipoproteins
LDLs carry
cholesterol from the liver to other tissues