lecture 29 - fatty acids as fuel molecules Flashcards
What is the preferred fuel source for red muscle?
fat
What is the preferred fuel source for white muscle?
glucose
What is the primary energy reserve in mammals?
Fats - as Triacylglycerols
What is excess energy consumed as glucose stored as in mammals?
As fat - TAGs
Why is fuel stored as fats rather than carbohydrates in the body?
They take up less space, and are more reduced than carbohydrates (more energy stored in the chemical bonds that is released when oxidised in pathways)
What form are fats delivered into the blood from adipose tissue when used for fuel?
Passively diffuses at free fatty acids and glycerol into the blood stream
In what form are free fatty acids transported in the blood?
They are hydrophobic, so travel bound to albumin as Albumin-FFA
Is delivery of fatty acids from the blood to tissues passive or active?
Passive
What form are fatty acids found in once transported into cells for use as fuel?
Bound to fatty acid binding proteins (FABP) as the cytosol is aqueous and FFA are hydrophobic.
Are fatty acids activated before or after beta-oxidation?
Before - before the FFA enters the mitochondria
How are free fatty acids activated?
Attached to CoA to make a fatty acyl-CoA
What provides the energy to activate fatty acids by adding CoA?
The hydrolysis of ATP to AMP (energy equivalent of 2 ATP)
What is the difference between a fatty acyl-CoA and an acetyl-CoA?
Fatty acyl-CoA has a carbon chain of any length, while acetyl-CoA always has a 2 carbon chain (and is therefore a type of fatty acetyl-CoA)
Where does fatty acid oxidation occur?
In the mitochondrial matrix
How does fatty acyl-CoA pass through the outer mitochondrial membrane?
Via a fatty acyl-CoA carrier
How does fatty acyl-CoA pass through the inner mitochondrial membrane?
Is converted to fatty acyl-carnitine, then passes through a carrier protein
What does the carnitine acyltransferease reaction facilitate?
The transport of fatty acyl-CoA from the inter-membrane space into the mitochondrial matrix by converting it to fatty acyl-carnitine
What enzyme catalyses the formation of fatty-acyl carnitine from fatty acyl-CoA and carnitine?
Carnitine acyltransferase
What are the reactants of the reversible carnitine acyltransferase reaction?
Fatty acyl-CoA and carnitine
What are the products of the reversible carnitine acyltransferase reaction?
Fatty acyl-carnitine and free CoA
what happens to a fatty acyl-CoA during the carnitine acyltransferase reaction?
Exchange of CoA and carnitine on a fatty acid
In what form must fatty acids be to undergo beta-oxidation?
Have an even number of carbons that are saturated (no double bonds)
Do fatty acids have an even or odd number of carbons when undergoing beta oxidation?
Even
Are fatty acids saturated or unsaturated when undergoing beta oxidation?
Saturated - no double bonds
Is ATP made in Beta-oxidation?
No (see exam diagram and there is no ATP included)
Where is energy released in beta-oxidation transferred?
To the coenzymes NAD and FAD
What happens to the fatty acid carbon chain during each round of Beta-oxidation?
Carbon chain split into 2
What is the final product of Beta-oxidation, and what happens to it?
Acetyl-CoA - is further oxidised in the citric acid cycle
What are the 4 stages of beta-oxidation?
Oxidation (1), Hydration (2), Oxidation (3), Cleavage (4)
What happens during the first reaction (oxidation) of Beta-oxidation?
Loss of 2 hydrogens to form a double bond - FAD reduced to FADH2
What happens during the second reaction (hydration) of Beta-oxidation?
H2O split across double bond adding a hydrogen and a hydroxyl group
What happens during the third reaction (oxidation) of Beta-oxidation?
Hydroxyl group converted to carbonyl group and NAD+ reduced to NADH and H+
What happens during the fourth reaction (cleavage) of Beta-oxidation?
Cleavage of molecule to release acetyl-CoA and add CoASH (free CoA) to remaining carbon chain, creating a 2 carbon shorter fatty acyl-CoA which enters the next round
What are the carbon products of beta-oxidation, one of which renters the cycle?
acetyl-CoA, 2 carbon shorter fatty acyl-CoA
How can the number of rounds of beta-oxidation undertaken by a fatty acid be calculated?
n(C)/2 -1 (the number of carbons, divided by 2, -1)
How many rounds of beta-oxidation is undertaken by palmitic acid (with 16 carbons)?
7
What are the products of each round of B-oxidation, excluding the carbon chain that enters the next round?
1NADH, 1FADH2, 1 acetyl-CoA
What are the overall products of the 7 rounds of beta-oxidation of palmitic acid?
7 NADH, 7FADH2, 8 acetyl-CoA
