Lipids 1-3 Flashcards
Lipids
Insoluble in water
Functions of lipids
Signalling molecules
Fat soluble vitamins eg A D E K
Activity of enzymes
Structural element of membranes
Classes of lipids
TAG, fatty acids, phospholipids, glycolipid and steroids
Fatty acid
Hydrophobic carbon and carboxyl
In vivo are double bonds usually cis or trans?
Cis
What is the terminal from methyl called?
Omega carbon
4 types of fatty acid
- good
- essential
- bad
- really bad
Good fat
Polyunsaturated fatty acid eg vegetable oil
Essential fatty acid
Lineolic and lineolic acid - humans cannot introduce double bonds past carbon 9
Aracidonic acid from lineolic acid needed for echosanoids
Bad fat
Saturated fat eg beef
Really bad fat
Trans fatty acids - hydrogenation of vegetable oil
TAG
3 fatty acid, glycerol
fuel and insulation
Phospholipids
fatty acid, phosphate and glycerol
amphipathic
What is the main dietary lipid?
TAG
Also fatty acids, cholesterol, cholesterol esters and phospholipids
Where is the main site of digestion?
Small intestine
What is TAG degraded by?
Pancreatic lipase to monoacylglycerol and 2 fatty acids
Cholesterol ester ==>
Cholesterol and fatty acid
Phospholipid =>
Fatty acid and lysophospholipid
What do the products form?
Mixed micelles by emulsification with bile salts (derived from cholesterol) and peristalsis
What happens to the micelle
Approaches brush border of intestine and release products which are resynthesized for export
Steatorrhea
Gall bladder removed so no bladder leading to excess fat in faeces - CF
Insoluble fatty acids repackaged into?
Chylomicrons for transport in the blood
What is TAG in chylomicrons broken down to?
Glycerol and fatty acids
What are the fatty acids not used by?
The brain
What happens to chylomicron without TAG
Go to the liver
What is fat in adipose tissue broken down to and by what?
fatty acids using hormone sensitive lipase
What is HSL activated and inactivated by?
Activated = phosphorylation in response to epinephrine inactivated = high blood glucose
How are fatty acids travelled in blood
Complex with albumin
Lipoproteins
4 classes of lipoprotein
- Huge chylomicron in liver
- VLDL
- LDL
- HDL
Where does beta oxidation occur?
Matrix of mitochondria
What does beta oxidation do and what are the products
Degrade fatty acids 2 carbons at a time
Acetyl coA, NADH and FADH2
Activation
Fatty acid activated in cytosol to fatty acyl coA
Transport
Cartinine shuttle as coA swapped as too big
Malonyl coA inhibits
Degradation
- Dehydrogenation FAD=>FADH2 double bond 2ATP
- Hydration
- dehydrogenation NAD=>NADH 3ATP
- thiolysis - acetyl coA 12ATP
Where do long chain fatty acids undergo preliminary oxidation?
Peroxisomes
Are fatty acids gluconeogenic?
No
What does excess acetyl coA produce?
Ketone bodies
When are ketone bodies used?
In starvation - cardiac, skeletal muscle and brain
Acetone - sweet smelling breath
Where are ketone bodies made?
Liver
What are fatty acids made from?
Acetyl coA
What are the fates of acetyl coA
- citric acid cycle
- steroids and cholesterol
- ketone bodies
Where does fatty acid synthesis occur?
Liver, lactating mammary glands and adipose tissue
CYTOSOL
What does fatty acid synthesis use?
ATP and NADPH
Shuttle
Citrate shuttle - acetyl coA in mitochondria so needs shuttled into cytosol
Occurs when citrate concentration is high
Product of fatty acid synthesis
Palmatic acid
Enzymes in fatty acid synthesis
Acetyl coA carboxylase
Fatty acid synthase
What is needed for malonyl coA synthesis?
Acetyl coA carboxylase - activated by citrate +insulin and inhibited by palmitoyl coA, Glucagon+epinephrine
What is used for cleaving?
Thioesterase
Name the steps
Elongation Reduction Dehydration Reduction Cleavage
Carrier protein in synthesis?
ACP
Steroid
Chemical substances synthesised by cholesterol
Eicosanoids
Derived from unsaturated fatty acids - omega 3/6
precursor to prostaglandins, leukotrienes and thromboxanes
Cholesterol fates
Steroids
vitamin D
Bile salts in liver
Prostaglandins
Uterine contraction
Pain and fever
Thromboxanes
Blood clotting
Leukotrienes
Prevent asthma by inhibition
