Lecture 26 - Fatty acids as a fuel molecule #2 Flashcards
Do adipose tissues make lipoproteins?
NO
What does adipose lipase do?
cleaves TAGs to give
three FFAs and glycerol
Are free fatty acids polar or non-polar?
non-polar
Where can fatty acids come from?
- diet or the liver
- storage in adipose tissue
How is the delivery of fatty acids to tissues?
- Adipose lipase makes FFA + Glycerol by cleaving TAG
- FFA passively travel in blood
- FFA bind albumin
- Transported to tissues passively
When are fatty acids activated?
before B-oxidation
When does fatty acid activation occur before or after entering the mitochondria?
Before
How are fatty acids activated?
By the attachment of CoA to make fatty acyl-CoA
What energy is required to CoA?
hydrolysis of ATP to AMP (energy equivalent of 2 ATP)
Oxidation of fatty acids occurs in the?
mitochondrial matrix
Movement between the cytosol and matrix
requires?
two membranes to be crossed
How are fatty acids transported to the mitochondrial matrix?
- The fatty acyl-CoA must pass through two membranes
- Outer membrane: uses fatty acyl-CoA carrier
- Inner membrane: requires the conversion to fatty acyl-carnitine
The carnitine acyltransferase reaction?
- Exchanges CoA and carnitine on a fatty acid
- Reversible reaction
Where does B-oxidation occur?
In mitochondrial matrix
What fatty acids does B-oxidation use?
fatty acids with an even number of carbons that are saturated (no double bonds)
Is ATP produced during B-oxidation?
No, ATP is not directly made in β-oxidation
What is energy released during B-oxidation transfered to?
the coenzymes NAD and FAD
What happens to the carbon chain during B-oxidation?
Is cut into two pieces
What is the product of B-oxidation?
acetyl-CoA
What happens to acetyl CoA?
is further oxidised in the citric acid cycle
What are the 4 steps of B-oxidation?
- Oxidation
- Hydration
- Oxidation
- Cleavage
What happens during the first reaction of B-oxidation (oxidation)?
Fatty acyl-CoA is oxidised forming a double bond, the 2x H atoms form FADH2 from FAD (FAD -> FADH2)
What happens during the second reaction of B-oxidation (hydration)?
Fatty acyl-CoA is hydrated by the addition of H2O, this breaks the double bond and puts an OH on one carbon and H on the other
What happens during the third reaction of B-oxidation (oxidation)?
Fatty acyl-CoA is oxidised, the O of the OH loses its hydrogen forming a double bond, and the carbon bonded to the O loses its hydrogen. (NAD+ -> NADH + H+)
What is FAD derived from?
Riboflavin (vitamin
B2)
What is FAD?
A coenzyme required by some
enzymes that catalyze redox
reactions (including fatty acid
oxidation, citric acid cycle)
What does FAD stand for?
Flavin adenine dinucleotide
Flavin coenzymes are ……
bound to the proteins with which they interact (flavoproteins)
tightly
What type of reduction does FAD undergo?
a two-electron reduction
(accepts two reducing equivalents)
What do the first three reactions of B-oxidation involve?
- rearrangement:
- energy captured (2 redox reactions)
- Overall alter chemistry around the bond for cleaving
in reaction 4
What occurs during reaction 4 (cleavage)?
is a cleavage between the ⍺
and β carbons
What is released during reaction 4?
Acetyl-CoA
What is added to the remaining carbon chain after the release of acetyl-CoA?
CoASH
What happens to the remaining fatty acyl-CoA after completion of cycle?
After becoming 2 carbons shorter it re-enters the B-oxidation cycle
What is released during one round of B-oxidation?
1 NADH + 1 FADH2 + 1 acetyl-CoA
How do you calculate the number of rounds of B-oxidation a FFA can undergo?
no. of rounds = n(C)/2 - 1
What are the products of 7 rounds of B-oxidation?
7 NADH, 7 FADH2 and 8 acetyl-CoA
