Fatty Acid Metabolism Flashcards
what are the functions of fatty acids?
energy storage and production
structural components of membranes
hormones derived from
carboxylic acid at one end & long C chain
saturated (no double bonds)
what is a saturated fatty acid?
with no double bond present in long C chain
what is an unsaturated fatty acid?
with one or more double bonds present
what is a lipid?
fatty acids conjugated with glycerol
linked to glycerol by ester bonds
what are esters?
linkages formed between a carboxylic acid and a alcohol group by the loss of water
what is glycerol?
3C
3 OH groups
common lipid skeleton
present in most lipids in body
not easy to transport around body
storage molecules
is triacylglyerol an energy source?
all tissues (not brain) can oxidise fatty acids to produce energy
TAG not used until glucose supplies are low
fatty acids transported in the blood complexed with serum albumin
equation of TAG breakdown?
TAG + 3h2o —> glycerol + 3 fatty acids
catalysed by triacylglycerol lipase
what are the steps in the oxidation of fatty acids?
step 1: free fatty acids I the systole are activated forming fatty acid acetyl coA
step 2: falty acyl coA uptake into mitochondria
step 3: B-oxidation pathway in mitochondrial matrix
Explain step 1
fatty acid activation
reacts with ATP & alpha phosphorus
intermediate with fatty acid AMP group attached via ester linkage
phosphates released as pyrophosphates -> phosphates
coA displaced, attach to fatty acid to make phosphodiester between
produces AMP
all at the cost of 2 ATPs
explain step 2
fatty acyl coA uptake by mitochondria
carnitine shuffle used to transport fatty acylcoA from cytoplasm to mitochondrial matrix
fatty coA reacts, add carnitine
allows transfer through
regenerate fatty acyl coA
explain step 3
B oxidation of fatty acids I mitochondria
C beta is oxidised
takes 2C off at a time and keeps going until nothing left
reaction 1 of step 3
- H removed from alpha and beta C by acyl coA dehydrogenase
- has FAD coenzyme
- e- delivered to coenzyme Q in transport chain
- take bond between alpha and beta c oxidase and make a double bond
- FADH2 used to make ATP
reaction 2 of step 3
- hydration of double bond
- produces hydroxyacyl coA
- hydrate the double bond, add -OH group on beta carbon
reaction 3 of step 3
- C-OH oxidised to C=O
- NADH formed oxidised by e- transport chain to produce ATP
- oxidise alcohol to form ketone, forming NAD
- changes beta C to ketone C
reaction 4 of step 3
- CoASH attacks beta C to produce acetyl coA and fatty acyl coA which is 2C smaller
- acetyl coA oxidised by citric acid cycle
- shortened fatty acid by 2C
process repeats until all of molecule converted
what is the ATP yield from oxidation of palmitate?
16 C
cost of 2 ATP
so 7 rounds of B-oxidation yields
8 acetyl coA - 8x10 ATP
7 NADH - 7x2.5 ATP
7 FADH2 - 7x1.5 ATP
= 108 ATP
so net yield of 106 ATP
Glyoxylate cycle
plants, fungi and bacteria convert acetyl coA to sugars through the glyoxylate cycle
happens in glyoxysomes
modified version of the citric acid cycle
equation of glyoxylate cycle
2 acetyl coA —> malate —> oxaloacetate
fatty acid synthesis
occurs in cytoplasm using different carrier
different coenzymes
different C2 donor/product
where does it occur?
in the cytoplasm
delivers acetyl coA from mitochondria to the cytoplasm
provides acetyl coA and NADPH in the cytoplasm
step 1 of synthesis
synthesis of malonyl coA
energy to form C-C bonds supplied indirectly by synthesising malonyl coA using ATP and CO2
catalysed by acetyl coA carboxylase
reacts with carbon dioxide
reaction 1 of synthesis
acetyl group acted using malonyl coA as donor
loss of CO2 drives reaction
malonyl coA synthesised by carboxylation of acetyl coA
2C longer
reaction 1 equation
acetyl coA + CO2 + ATP —> malonyl CoA + ADP + Pi
