Lipids Flashcards
What are the functions of lipids within the body?
- Storage of energy
- Structural component of cell membranes
- Signalling molecules
- Hormones
- Vitamins A,D,E and K
- Enzyme Cofactors
What are the 5 main classes of lipids?
- Fatty acids
- Triacylglycerol
- Phospholipids
- Glycolipids
- Steroids
What are essential fatty acids?
Fatty acids which must be taken in the diet from plants.
E.g. linoleic and alpha linoleic
What is meant by BAD fats?
Fats with a high saturated fat content
What is meant by GOOD fats?
Fats with a high polyunsaturated fat content.
E.g. vegetable oil
What is meant by trans fats?
Man made saturated fats from the hydrogenation of unsaturated fats.
What is the difference between saturated and unsaturated fats.
Unsaturated fats contain C=C, resulting in kinks in the fatty acid chain. This leads to a decrease in melting point. These fats are liquid at room temp.
Saturated fats do not contain double bonds. As a result, they have a straight chain and so a higher melting point. They are solid at room temperature.
What is the major health benefit of omega-3 intake?
Omega-3 (derived from linoleic acid) lowers plasma cholesterol, to prevent atherosclerosis.
How are triacylglycerols formed?
Esterification of 3 fatty acids with a glycerol molecule.
How are phospholipids formed?
Esterification of one glycerol molecule with 2 fatty acids and a phosphate molecule.
Why are phospholipids considered amphipathic molecules?
They contain a hydrophilic (phosphate) head and a hydrophobic (fatty acid) tail
What is the role of bile salts on lipid digestion?
Bile salts act as biological detergents, forming emulsions and allowing mixed micelles.
What are the digestive products of triacylglycerols?
Monoacylglycerol and 2 Fatty acids
Where is the main site of digestion of TAGs?
Small intestine
What are the products of phospholipid digestion in the body?
Lysophospholipid and one fatty acid
What are the products of cholesterol ester digestion in the body?
Cholesterol and free fatty acid
What is steatorrhea and why does it occur?
Steatorrhea is excess fat in the stool and is caused by lipid malabsorption due to defects in bile secretion, pancreatic function or intestinal cell uptake
What path is taken by the digestive products of triacylglycerols?
- Fatty acids and glycerols are taken up by intestinal mucosa
- Used to resynthesize TAG.
- TAG insoluble and so packaged into chylomicrons for transport
- Transported to blood stream via lymphatic system
- TAG in chylomicron is hydrolysed to FAs and glycerol
- FAs enter cells and are either utilised as a fuel source or esterified to TAG for storage.
- Glycerol is used by the liver to synthesis Glycerol-3-phosphate for glycolysis/ gluconeogenesis
What enzyme is used to release FA from stored TAG?
Hormone sensitive lipase (HSL)
Where does B oxidation occur?
Cytosol and Mitochondrial matrix
What is the aim of B oxidation?
To degrade fatty acid molecules 2 carbons at a time to create acetyl CoA and reduced NAD and FAD
What are the three main steps to B oxidation?
- Activation of FA to form Fatty acyl CoA
- Transport of longer chain fatty acyl CoA from cytosol to mitochondrial matrix via carnitine shuttle
- Degradation of fatty acyl CoA to form 2C acetyl CoA
What substance inhibits carnitine shuttle function and why?
Malonyl CoA inhibits Carnitine shuttle function.
Malonyl CoA is required for fatty acid synthesis and so it prevents synthesis and degradation occurring simultaneously.
How many reduced NAD/ FADs are produced per B oxidation reaction?
One NADH and one FADH2
