lipids 1 Flashcards
(30 cards)
In what three places do lipids exist?
- cell membranes
- as lipid droplets in adipose tissue
- in blood lipoproteins
Name the 6 biological functions of lipids
- stored form of energy
- structural element of membranes
- enzyme cofactors
- hormones
- vitamins A, D, E, K
- signalling molecules
What are the classes of lipids?
fatty acids triacylglycerol phospholipid glycolipid steroids
What does ‘18:1’ mean in terms of fatty acid nomenclature?
18 carbons and 1 double bond
what are linoleic and linolenic acids examples of?
essential fatty acids in humans
Why must some fatty acids be consumed in the diet?
humans cannot introduce double bonds beyond carbon 9
what 2 benefits does Omega-3 fatty acid have?
1 - lowers plasma cholesterol and prevents atherosclerosis
2- lowers triacylglycerol and prevents obesity
what are triacylglycerols esters of?
fatty acids and glycerol
what is phospholipid composed of?
glycerol bonded to two fatty acids and a phosphate group
what is the main dietary lipid?
triacylglycerol
what is the main site of digestion?
small intestine
what role do bile salts play in lipid digestion?
act as biological detergents to form emulsions and mixed micelles
what enzyme degrades TAG to monoacylglycerol and two fatty acids in the small intestine?
pancreatic lipase
What is the second product of digestion of cholesterol esters as well as free fatty acid?
cholesterol
What do phospholipids hydrolyse to?
fatty acid and lysophospholipid
what do products of lipid digestion form with bile salts in order to be absorbed?
mixed micelles
what is Steatorrhea?
excess fat in faeces
which three defects could lead to lipids not being absorbed by cells and potentially steatorrhea?
defects in:
- bile secretion (for secreting bile salts to form mixed micelles and emulsify the fat)
- pancreatic function (for breaking down molecule)
- intestinal cell uptake
The intestinal cells resynthesize TAG, PL and CE for export but they are insoluble. How is this problem overcome?
The are packaged with apoB-48 into chylomicrons
How are chylomicrons released from intestinal cells and where to?
by exocytosis
into lymph then blood
which enzyme hydrolyses TAG in chylomicrons to FA and glycerol?
lipoprotein lipase
what are chylomicrons depleted of TAG called and where do they go?
chylomicron remnants
go to liver
what two things can happen to fatty acids (those made when TAG is broken down by lipoprotein lipase)
- oxidised as fuel
- re-esterified for storage
in what form is TAG stored in adipose cells?
as droplets
