intro to FA synthesis Flashcards
where does the majority of FA come from
diet
what do we do with exess protein or carb
convert to FA and store them
where does FA synthesis occur
in liver, adipose tissue, lactating mammary glands
where does FA biosynthesis take place
in the cytoplasm
what facilitates the elongation of FA chain
FAS 1
what is required for carboxylation steps of FA synthesis
ATP
what powers reduction steps in FA synthesis
NADPH
in what kind of organism does FA synthesis and breakdown occur in different cellular compartments
in eukarytoes
where does FA breakdown occur
mitochondria
where does FA synthesis occur
cytosol
what is catalyzed by different sets of enxymes
FA breakdown and biosynthesis
what are the starting materials for FA biosynthesis
malonyl CoA and acetyl CoA
commitment, rate limiting, and regulation step- what enzyme does ths
Acetyl CoA carboxylase
what catalyzse the irreversible formation of malonylcoa from acetyl coa
Acetyl CoA carboxylase
what prosthetic group does Acetyl CoA carboxylase contain
biotin- Vit B7
what does Acetyl CoA carboxylase do
transfers carboxyl group from HCO3/ bicarbonate to biotin in ATP dependant reaction
what does Acetyl CoA carboxylase need to work
ATP
what happens after transfers carboxyl group from HCO3/ bicarbonate to biotin in ATP dependant reaction
carboxyl group is carried by biotin to different active site where CO2 is transferred to acetyl CoA to yiled malonyl coA
what is acetyl coa brought into the cytoplasm as
citrate
what is the purpose of making malonyl CoA
to make subsequent steps more thermodynamically favourable
what domain does carboxyl group add onto biotin
in the biotin carboxylase domain
what initially attatches the growing FA chain to the enzyme
thioester linkage via 2 thiol groups
how many enzymes catalyze each cycle to FA synthesis
4
what are the four steps of FA synthesis
- condensation of growing chain with activates acetate
- reduction of cabonyl to hydroxyl
3.dehydration of alcohol to trans alkene - reduction of alkene to alkane
what do the reduction steps do with respect to electron carriers
use elentrols from NADPH + H and make NADP+`
by how many carbons does each subsequent elongation step increase the length of FA by
2
when does FA synthesis stop
at 16 carbons
FAS 1 polypeptide structure
single polypeptide chain which contains 7 catalytic site each with differnt function
homodimer function in FAS1
each function independantly
where is ACP
domain in FAS1
what shuttles acyl group from one active site to another in sequence- covalently linked to acyl group
ACP
what is vit B5 derivative attatched to
ACP
what does vit B5 derivative contain
SH group that allows for attatchement to acetyl coa to donate atoms to growing chain
Preparatory Step in FA biosynthesis
Acetyl CoA and malonyl CoA (or longer fatty acyl chain
in later steps) are bound to FAS I
– CoA portions are lost
– bind via thioester terminus of the FAS I on ACP
