Lipid Metabolism Flashcards
What are the two types of fatty acids and which can be essential?
- Saturated and unsaturated
- Certain unsaturated FAs are essential dietary components eg arachidonic acid for eicosanoid synthesis
What are the three groups of lipid?
- FA derivatives (TAGs, FAs, Phospholipids, Eicosanoids -local mediators)
- Hydroxy-methyl-glutaric acid derviatives (Ketone bodies, cholesterol, cholesterol esters and bile acids/salts
- Vitamins A, D, E and K
Are lipids soluble or insoluble in water?
-Insoluble as they are hydrophobic
What are lipids synthesised from?
-1 glycerol and three FAs by esterification
What is the main use of lipids
-Fuel store
Are lipids or carbs more reduced?
Lipids
Lipid synthesis is under what type of control; give examples
- Hormonal control
- Insulin increases synthesis
- Glucagon, adrenaline and cortisol decrease synthesis
What is the first stage in lipid metabolism?
- Hydrolysing dietary lipids extracellularly by pancreatic lipase in the small intestine (lipolysis)
- Complex - involves bile salts and cofactor colipase
What are the products of lipolysis?
- 1 glycerol
- 3 FAs
What happens to glycerol after lipolysis?
-Enters bloodstream
-Transported to liver for metabolism
-Metabolised into DHAP and enters glycolysis
OR
-Metabolised into glycerol phosphate and enters TAG synthesis
What is stage 2 in lipid metabolism and where does it occur?
- FA catabolism
- FA carried to the tissues in the bloodstream bound to albumin
- Occurs in liver, heart and skeletal muscle as they have high mitochondria
Why does FA catabolism not occur in the CNS or RBCs?
- RBCs have no mitochondria
- FAs cannot readily cross BBB
Describe the first step in FA catabolism
- FA activation
- Activated by linking a CoA molecule with S-H to a FA
- CoAS-H has a high energy bond of hydrolysis which acitvates the FA
What is the activated FA product of FA catabolism?
-Fatty acyl-CoA
What two things does FA activation require for the reaction to happen?
- ATP
- Fatty acyl CoA synthase
What is the second step in FA catabolism
-Carnitine shuttle into mitochondrial matrix
Why does fatty acyl coA require a carnitine shuttle into the mitochondrial matrix?
-Does not readily cross the inner mitochondrial membrane
Describe the process of FA transport into the mitochondrial matrix
- Fatty acyl coA + Carnitine -> Acyl carnitine
- Catalysed by carnitine acyl transferase 1
- Acyl carnitine + coA -> Fatty acyl Co A + carnitine
- Catalysed by CAT 2
- Requires CoA to be in matrix
How does the carnitine shuttle regulate FA oxidation?
- Regulates the rate at which FA enter the matrix
- Transport is inhibited by malonly-CoA, an intermediate of FA synthesis
- Ensures that newly synthesised FAs are not being immediately oxidised
What is the third step in FA catabolism once FA are in the mitochondrial matrix?
-B-oxidation
What are the important end products of B-oxidation?
-Acetyl coA, NADH and FADH2
What does B-Oxidation require to work?
-NAD+, FAD+ and O2
What is B-Oxidation?
- A sequence of oxidation reactions in which FAs are oxidised and C2 is removed in a stepwise fasion until only C2 remains
- All intermediate products are linked to CoA
- All C2 get converted to acetyl coA
- Releases high amount of free energy captured by NAD+ and FAD+
Name the three ketone bodies produced from Acetyl CoA?
- Acetoacetate
- Acetone
- B-Hydroxybuterate
