Fatty Acid Metabolism Flashcards
What is the function of fatty acids?
- Energy storage and production
- Structural components of membranes
- Some hormones are derived from fatty acids
What is a saturated fatty acid?
no double bonds
What is an unsaturated fatty acids?
One or more double bonds
Do fatty acids normally have an even or odd number of C atoms?
Even
What is aliphatic?
Composed of hydrogen and carbons
What are fatty acids made of?
Aliphatic side chain
Acidic head
What is an acidic head?
carboxylic acid
Are saturated fatty acids better than unsaturated fatty acids?
No, unsaturated fatty acids are better
What are lipids?
A mixture of fatty acids and glycerol
What does a triacylglycerol consist of?
- 3 fatty acids
- On glycerol
Linked by ester bonds
What are esters?
Linkages formed between a carboxylic acid (-COOH) and alcohol –OH) groups by loss of water
Are lipids hydrophilic or hydrophobic?
Hydrophobic
Are lipids easy or hard to transport?
Hard
What can triacylglycerol be?
An energy source
What can all tissues except the brain do?
Oxidise fatty acids derived from triacylglycerol to produce energy
When is triacylglycerol used?
When glucose supplies are low
triacylglycerol + 3H2O =
Glycerol and 3 fatty acids
How is lipase activated?
Normally by glucagon
How are fatty acids transported?
In the blood complexed with serum albumin
What are the three step process of oxidation of fatty acids?
Step 1: Free fatty acids in the cytosol are activated forming fatty acyl-CoA
Step 2: Fatty acyl-CoA uptake into mitochondria.
Step 3: b-oxidation pathway in mitochondrial matrix
What happens in the first stage of oxidation of fatty acids?
- Oxygen from fatty acid attacks phosphorus
- Releases inorganic pyrophosphate
- AMP and fatty acid attached (bonded together by ester bond)
- Co-A reacts with acyladenylate mixed anhydride where AMP is rejected and fatty acyl-co A is formed
What happens in the second stage of oxidation of fatty acids?
- Fatty acid oxidised by mitochondria (in mammals)
- The inner mitochondrial membrane is not permeable to fatty acids or fatty acyl CoA
- So the carnitine shuttle is used to transport fatty acyl CoA from the cytoplasm to the mitochondrial matrix.
What happens in the third stage of oxidation of fatty acids?
- Beta (C3) carbon oxidised
- H removed from a and B carbons by acyl CoA dehydrogenase (contains FAD cofactor)
- Electrons delivered to coenzyme Q in electron transport chain
- Hydration of double bond (addition of water). To produce hydroxyacyl-CoA
- C-OH oxidised to C=O
- NADH formed is oxidised by electron transport chain to produce ATP
- CoASH attacks b carbon to produce acetyl CoA and a fatty acyl CoA which is now 2 C atoms shorter.
- Acetyl CoA oxidised by citric acid cycle.
What is important about step 3 of oxidation of fatty acids?
Even chain fatty acids this process repeats until all of the molecule is converted into acetyl CoA
What is the net yield of ATP in oxidation of fatty acids?
106 ATP
How many ATPs are generated per acetyl CoA?
10
What does the glyoxylate cycle allow?
Plants, fungi and bacteria to make sugar from fatty acids
What can plants, fungi and bacteria that animals cant?
Convert acetyl CoA
Where does glyoxylate cycle operate?
Glyoxysomes
What is the overall reaction of glyxoylate cycle?
2 Acetyl CoA —-> malate —-> oxaloacetate
What can mammals create glucose from?
Propionyle CoA
What do odd chain length of fatty acids yield?
Acetyl CoA and propionyl CoA
Where does B oxidation occur?
in the mitochondrion
Where does biosynthesis take place?
Cytoplasm
How are B oxidation and biosynthesis similar?
Same intermediates
How are B oxidation and biosynthesis different?
-Occurs in the cytoplasm using a different carrier (acyl carrier protein (ACP) instead of CoA), different cofactors (NADP+ instead of FAD and NAD+) and a different C2 donor/product (malonyl CoA instead of acetyl CoA).
What does the pirate shuttle deliver?
Acetyl CoA from the mitochondria to the cytoplasm.
Describe the process of fatty acid synthesis:
- Energy to form C-C bonds is supplied indirectly by synthesizing malonyl CoA from acetyl CoA using ATP and CO2 (catalyzed by Acetyl CoA carboxylase )
- The C=O group on C3 (b carbon) is reduced to C-OH by NADPH.
- Dehydration (removal of water) – generates a double bond between the a and b carbons (C2 and C3).
- Reduction of double bond to single bond
- fatty acyl-ACP, now 2C longer, can re-enter the process OR the process is stopped by removing ACP (using fatty acyl-ACP thioesterase)
What is fatty acid synthase?
- single multifunctional enzyme
- Exists as dimers
- Arrangement eases movement of fatty acyl chain through the complex process
- Anchored to ACP
Is Acetyl CoA carboxylase is tightly regulated?
Yes
How is Acetyl CoA carboxylase is tightly regulated?
- inhibited by phosphorylation
- controlled by glucagon and adrenaline.
How does insulin signalling favour fatty acid synthesis?
Activating a phosphatase that dephosphorylates acetyl CoA carboxylase
Finish the sentence:
Fatty acid synthesis and breakdown are …
reciprocally regulated
What does glucagon promote in fatty acids?
Release of fatty acids from adipocytes
