29 Flashcards
What is the preferred fuel for most tissue ? What do red vs white muscle use?
Fatty acids are the preferred fuel for most tissues Red muscle cells tend to use fat (white muscle cells tend to use glucose)
What is the primary energy resource in mammals
Fa t is the primary energy reserve in mammals
- TAG (triacylglycerols)
- 5 to 25% body weight
Excess energy consumed as glucose is stored as fat
Why store fuel as fats?
Fatty acids are more reduced than carbohydrates (more energy released when oxidized in pathways)
Stored carbohydrate (glycogen) is approximately 2/3 water - as they are polar so take up more space to be stored
(Fat is non polar)
Delivery of fatty acids for fuel - yappage - ADIPOSE TISSUE —> blood
- body needs the energy and wats to take fat out of storage
- signals activate a lipase enzyme which will chops fatty acids off a glycerol (ends up with free fatty acids and a glycerol)
- conc of FFA and glycerol is increasing so it has to passively diffuse into the blood
- glycerol goes to the liver
- blood is mainly water hence polar, thus hydrophobic fatty acids need the protein albumin-FFA for it to be carried to the tissues
- albumin has polar side chains on the exterior and hydrophobic pockets in the middle for the FFA to sit in
Delivery of fatty acids for fuel - BLOOD —> CELL
- in tissues concentration of fuel molecules are low
- free fatty acids can move out of the blood and into the tissues
- once in tissue cross cell membrane into cell
- some small fatty acids can diffuse themselves but usually fatty acid to help them
- free fatty acid is in cell, cytosol in polar fatty acid is non polar - binds to FABP
When does fatty acid activation happen
Fatty acids are activated before β-oxidation Occurs before the fatty acid enters the mitochondria
How are fatty acids activated?
Activated by attachment to CoA to make a fatty acyl-CoA
Energy to add CoA from hydrolysis of ATP to AMP (energy equivalent of 2 ATP)
Difference between the carbon chain of of fatty acetatyl coA and acetyl-coa
fatty acyl-CoA: a carbon chain of any length
acetyl-CoA: a two-carbon chain
Where does the energy for addition of CoA in fatty acid oxidation come from?
Energy to add CoA from hydrolysis of ATP to AMP (energy equivalent of 2 ATP)
Movement between the cytosol and matrix requires _____ membranes to be crossed
Two
Transport of fatty acids into the mitochondrial matrix- what needs to happen?
The fatty acyl-CoA must pass through two membranes Outer membrane: fatty acyl-CoA carrier Inner membrane: requires the conversion to fatty acyl-carnitine (can then travel through the fatty acrylic-carnatine through the membrane)
(Once on the other side carnitine is chopped off by carnitine acylttransferase and will then be recycles and fatty acrylic-coa is now activated and in the right place)
The carnitine acyltransferase reaction
(How fatty acid gets through the second membrane)
Exchanges CoA and carnitine on a fatty acid
Reversible reaction - can put the CoA back on
Requirements for fatty acids undergoing B-oxidation
β-oxidation uses fatty acids with an even number of
carbons that are saturated (no double bonds)
Is there ATP DIRECTLY made in B-oxidation
No ATP is directly made in β-oxidation
Diagram of the first 3 reactions of B-oxidation
B-oxidation reactions 1-3 - what does in involve
i nvolve a rearrangement:
- energy captured (2 redox reactions)
- the chemistry around the bond is altered so it can be cleaved in reaction 4
Reaction 4 of B-oxidation
is a cleavage between the ⍺ and β carbons
- acetyl-CoA released
- CoASH added to remaining carbon chain
- 2 carbon shorter fatty acyl-CoA enters next round
How to figure out number of rounds of B-oxidation
of rounds = n(C)/2 - 1
