Lipids Flashcards
What do triacylglycerols consist of?
3 fatty acid chains esterified to glycerol
What are the three classes of lipids and what is in each one?
Fatty acid derivatives - fatty acids, triacylglycerols, phospholipids, eicosanoids
Hydroxymethylglutaric derivatives - ketone bodies, cholesterol, cholesterol esters, bile acids and salts
Vitamins - ADEK
What reaction does glycerol kinase do?
Glycerol -> glycerol phosphate
Occurs in the liver
What is lipolysis?
When triacylglycerols in adipose tissue are hydrolysed by hormone-sensitive lipase to produce fatty acids and glycerol
How are fatty acids transported in the bloodstream
Bound non-covalently to albumin
Where are the products of lipolysis transported to?
Fatty acids - tissue
Glycerol - liver
Where does beta-oxidation occur?
Mitochondria
What must happen to fatty acids before they are oxidised?
Need to be activated.
Bonded to coenzyme A via the S atom in the coenzyme
Forms a high energy hydrolysis bond.
What does the activation of fatty acids require?
ATP
Fatty acyl CoA synthase
Where is fatty acid oxidation done and what are the consequences of this?
Outside the mitochondrion
Shuttled in via cartinine
Can be used to control the rate of FA oxidation and their entry into the mitochondrion
What are the consequence of a defective mitochondrial fatty acid transport system for a patient?
Low exercise tolerance
Large amounts of TAGs in muscle
What inhibits FA transport?
Malonyl CoA, an intermediate in fatty acid synthesis
What happens in the beta oxidation of fatty acids?
Sequence of reactions that oxidise the FAs and removes a C2 unit each time
Cycle repeats until two C atoms remain
In beta oxidation, what are the C atoms which are removed converted into?
Acetyl CoA
What are all the intermediates in the beta oxidation pathway linked to?
Coenzyme A
What produces acetyl CoA?
Catabolism of fatty acids, sugars, alcohol, and certain amino acids. Also an intermediate in lipid biosynthesis
Which lipids cannot be synthesised in the body?
Polyunsaturated fatty acids
Where are lipids synthesised?
Liver and some in adipose tissue
Name the three ketone bodies produced
Acetone
Acetoacetate
Beta-hydroxbutyrate
How are the three ketone bodies synthesised?
Acetoacetate and beta-hydroxybutyrate are produced in the liver from acetyl CoA
Acetone arises from spontaneous decarboxylation of acetoacetate
When does the concentration of ketone bodies increase?
Starvation
Untreated type 1 diabetes
When insulin levels are high and glucagon is low, what is acetyl CoA converted into and by which enzyme?
Cholesterol
Reductase
When insulin is low and glucagon is high, what is acetyl CoA converted into and by which enzyme?
Ketone bodies
Lyase
By which tissues can ketone bodies be used as an energy source?
All tissues containing mitochondria - even the CNS
When being used for energy, what happens to the ketone bodies?
Converted to acetyl CoA and this goes through stage 3 catabolism (Krebs Cycle)
