Exam 4 Flashcards
Principle Stored Energy Reserve
Triacylglycerols
Structure of Fatty Acids
CH3(CH2)COO
- Generally even number of carbon atoms
- Odd and trans Fats are less common
- around 90% are esterified and 10% flow freely attached to Serum Albumin in the blood
- More degrees of unsaturation= more fluid
- longer= less fluid
Linoleate
18: 2 delta 9,12
- essential FA
linolenate
18: 3 delta 9,12,15
- essential FA
Omega carbon
carbon at the end of a FA chain
Where FAs are synthesized
In the liver and mammary glands
- only in the cytosol of cells
- requires the transport of Acetyl CoA into the cytosol via the citrate transport
FA synthesis require ___ and ____ as energy sources
ATP and NADPH
FA are synthesized from ______ derived from _____ and _____
Acetyl CoA derived from excess protein and carbohydrates
Citrate is Shuttled in ….
High energy states. ATP will inhibit the isocitrate dehydrogenase enzyme and citrate that accumulated can then be shuttled out to make FAs
Overview of Fatty Acid Synthesis
2 acetyl Coa-> Reduction-> dehydration-> reduction-> condensation
Acetyl CoA carboxylase
Acetyl Coa-> malonyl CoA in FA synthesis
- requires ATP
- HCO3
- Biotin cofactor
ACC Allosteric control
Polymer stabilization via Citrate and destabilization via Fatty Acyl CoA
ACC regulation via Phosphorylation
- Regulated via cAMP, epinephrine, and protein kinase cascade
- These and AMP will all deactivate the ACC via a AMPK in the Fasted state
- Dephosphorylation of ACC occurs in the presence of insulin
Fatty Acyl Synthase Complex
- Single polypeptide (Dimer) in Humans with 7 activities
- Can be multiple polypeptides in Plants, Yeast, and Bacteria
ACP structure
Very similar structure to CoA and shares the phosphopantetheine group but is attached to serine instead of an adenosine
FA synthesis Charging step
- Malonyl/ Acetyl CoA ACP Transferase (MAT)
1. Transfers Acetyl CoA to the ACP domain
2. Acetyl group then gets transfered to the beta- keto acyl ACP synthase (KS) domain
3. Malonyl/ Acetyl CoA ACP Transferase then adds an malonyl CoA to the ACP domain
FA synthesis Condensation Step
- Decarboxylation of the malonyl CoA allows for the nucleophilic attack for the acetyl group carbonyl group
- Forms Beta-ketobutyryl ACP
Suppose 14C-labeled CO2 is used to form malonyl-CoA from acetyl-CoA. If this labeled malonyl CoA is used for palmitate synthesis, which carbon atom(s) in the fatty acid would be radiolabeled?
NONE
First Reduction in FA synthesis
- B ketobutyryl ACP reductase
- Uses an NADPH
- Forms B-hydroxybutyryl- ACP
FA synthesis Dehydration
- Occurs via the B-hydroxybutyryl ACP dehydratase (DH)
- Removes a water molecule
- Form Trans-delta2- butenoyl-ACP
Second reduction in FA synthesis
- Uses the Enoyl-ACP reductase (ER)
- Forms Butyryl-ACP
- Uses NADPH
NADPH sources
- PPP pathway
- Malic enzyme in the cytosol
- Converts Malate to pyruvate for import into the mitochondria
Elongation and desaturation of palmitate
- Occurs in the smooth ER
- Cannot desaturate past carbon 9
- desaturations occur via Fattyl Acyl CoA desaturates which are mixed function oxidases that generate H2O and require O2
Respiratory Distress Syndrome
- Failure to synthesize enough dipalmitoyl phosphatidylcholine
- DPPC is generally used to reduce the surface tension in the fluid surrounding the alveoli
