Lipds Flashcards
Where are lipids found?
Lipid droplets in adipose tissue, cell membrane, blood lipoproteins
Functions of lipids
- Stored form of energy
- Structural element of membranes
- Enzyme cofactors
- Steroid Hormones
- Vitamins A,D,E,K
- Signalling molecules
Lipid Classes
- Stored form of energy
- Structural element of membranes
- Enzyme cofactors
- Steroid Hormones
- Vitamins A,D,E,K
- Signalling molecules
Main dietary lipid
Triacylglycerol
What are bile salts?
Biological detergents to form emulsions and mixed micelles
Digestion of Triacylglycerol
Monoacylglycerol + 2 Fatty Acids
in small intestine by Pancreatic Lipase
Cholesterol Ester digestion
Cholesterol & Free fatty acids
Phospholipid digestion
Hydrolysed into fatty acids & lysophospholipids
Uptake of digested lipids
-Product of lipid digestion + bile salts -> mixed micelles
-Lipid products enter enterocytes via diffusion
(short & medium fatty acids don’t require micelles for diffusion)
What happens to dietary lipids?
Lipids are solubilised by apoB-48 into chylomicrons
What happens to dietary lipids?
Lipids are solubilised by apoB-48 into chylomicrons
What happens to chylomicrons?
Hydrolysed by lipoprotein lipase into fatty acid & glycerol
Release of energy from stored Triacylglycerol
Triacylglycerol -> Fatty acids [Hormone Sensitive Lipase]
Lipoprotein classes
- Chylomicrons - TAG rich (carry TAG from intestine to tissue)
- VLDL - TAG rich (carry TAG from liver to tissue)
- LDL - Cholesterol rich (cholesterol to extrahepatic tissue [outside liver])
- HDL - Protein / Cholesterol rich (transport cholesterol from tissue to liver for elimination)
Lipoprotein classes
- Chylomicrons - TAG rich (carry TAG from intestine to tissue)
- VLDL - TAG rich (carry TAG from liver to tissue)
- LDL - Cholesterol rich (cholesterol to extrahepatic tissue [outside liver])
- HDL - Protein / Cholesterol rich (transport cholesterol from tissue to liver for elimination)
How are lipids transported
Lipoproteins
Steps of Beta-Oxidation
(1) Activation of fatty acid in cytosol
(2) Transport into the mitochondria
(3) Degradation of two carbon fragments (as acetyl CoA) in the mitochondrial matrix
Transport by Carnitine Shuttle
- Fatty acyl CoA gives CoA to Carnitine [Carnitine Palmitoyl Transferase]
- Fatty Acyl Carnitine moves into mitochondrial matrix via Carnitine Translocase Molecule
- Carnitine replaced with CoA
Beta-Oxidation Degradation steps
(1) Dehydrogenation, produces FADH2
(2) Hydration
(3) Dehydrogenation, produces NADH
(4) Thiolysis (cleaved), produces acetyl CoA
Why does Beta-Oxidation occur?
Provides energy for skeletal/heart muscle & kidneys when glucose / glycogen / gluconeogenic precursors become scarce
Main ketone bodies
3-Hydroxybutyrate, Acetoacetate
Main ketone bodies
3-Hydroxybutyrate, Acetoacetate
What uses ketones for energy?
Cardiac/ skeletal muscles, kidneys, brain cells
Where does Fatty Acid Synthesis occur?
Liver, Lactating mammary gland, adipose tissue
Requirements for Fatty Acid Synthesis
- Acetyl CoA Carboxylase (activation / regulation)
- Fatty Acid synthase (multifunctional enzyme)
- Acetyl CoA
- NADPH
Product of Fatty Acid synthesis
Palmitic Acid
Overall reaction for palmitate
8 Acetyl CoA + 14 NADPH + 14 H+ + 7 ATP
-> Palmitate + 8 CoA + 14 NADP+ +7 ADP + 7 Pi + 7 H2O
Fates of Fatty Acids
- Combine with glycerol -> Triacylglycerol
- Triacylglycerol + proteins + phospholipids + cholesterol ester -> VLDL
Steroid classes
- Cholesterol
- Steroid Hormones
- Bile salts
Cholesterol function
- Component of cell membrane
- Precursor to other substances
Eicosanoids function
Signalling molecules, derived from omega-3 or omega-6 fatty acids
