Lipids 1
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Lipids are:
Heterogenous A stored form of energy Needed as enzyme cofactors Used in hormones Used for the synthesis of Vitamins A, D, E and K Used as signalling molecules
Define the major lipid classes (5)
FATTY ACIDS: [Essential fatty acids (need to come from diet) Good fats (polyunsaturated) Bad fats (High in saturated fats) Really bad fats (trans fatty acids)] TRIGLYCERIDES PHOSPHOLIPIDS GLYCOLIPIDS STEROIDS
Why do essential fatty acids need to come from our diet?
Humans cannot introduce DOUBLE BONDS beyond carbon number 9
State what is meant by a triglyceride
ESTER of 3 fatty acids + glycerol (water insoluble)
Triglycerides are a major component of
Adipose tissue
State what phospholipids are composed of
Glycerol bonded to 2 fatty acids and 1 phosphate group
How do lipids exist in cell membranes
In blood as lipoproteins As lipid droplets in adipose tissue
Linoleic acid is an example of
An essential fatty acid
Margarine is
A trans fat
Arachidonic acid is
An omega 6 fatty acid synthesised from linoleic acid
Omega 3 fatty acids are derived from
Linoleic acid as essential fatty acids
What do omega 3 fatty acids do?
Lower plasma cholesterol preventing atherosclerosis Lowers TAG preventing obesity Reduces inflammation
State some clinical symptoms of essential fatty acid deficiency
Growth retardation, reproductive failure, skin lesions, kidney and liver disorders, subtle neurological and visual problems
Essential fatty acid deficiency can cause chronic disease of the
Intestine
Omega 3 deficiency can lead to
Depression and hyperactivity
State the main dietary lipid
Triglycerols
State the other less common dietary lipid
Phospholipids Cholesterol Cholesterol esters Free fatty acids
State where most lipid digestion occurs
Small intestine
State what brings about lipid digestion
Pancreatic enzymes (lipases) Emulsification by bile salts (dispersion) Peristalsis (mixing)
What do saturated fats play a huge role in
Myelination of nerve fibres and Hormone production
Describe the process of lipid digestion
Main site = small intestine Requirements = pancreatic enzymes (lipase), emulsification by bile salts and peristalsis Process: Most triglycerides are digested by pancreatic lipase into 1 monoglyceride + 2 fatty acids. Cholesterol esters are broken down to cholesterol and fatty acid. Phospholipids are hydrolysed to a fatty acid and a lysophospholipid.
Describe the process of lipid absorption
Products of lipid digestion form mixed micelles with bile salts (long chain fatty acids) Mixed micelles approach the brush border membrane of enterocytes and release lipid products which enter cells by DIFFUSION
State the role of bile salts during lipid digestion.
Emulsification
State what is meant by Steatorrhea.
The presence of excess fat in the faeces