Lipid metabolism- Fatty acid synthesis through the malonyl pathway

?
Where does fatty acid synthesis take place?
In the cytoplasm
1 of 20
What does fatty acid synthesis require?
CO2, co-factors (Biotin) and reducing power (NADPH)
2 of 20
What is the starting point for fatty acid synthesis?
Acetyl CoA (Which is converted to malonyl CoA)
3 of 20
What is the malonyl pathway?
A repeated cycle of 4 reactions (Opposite to B-oxidation) with an extension of 2 carbon atoms per cycle
4 of 20
How is acetyl CoA transported into the cytoplasm?
In the form of citrate- In mitochondria, acetyl CoA condenses with oxaloacetate, (Enzyme: Citrate synthase), citrate is formed and transported to the cytoplasm
5 of 20
Once the citrate is in the cytoplasm, what needs to happen in order for acetyl CoA to be used in fatty acid synthesis?
Citrate is cleaved to become oxaloacetate and acetyl CoA, (Enzyme: ATP-citrate lipase)
6 of 20
What happens once the acetyl CoA is in the cytoplasm?
It need to be carboxylated to malonyl CoA, (Enzyme: acetyl CoA carboxylase), requires CO2, biotin and energy (1ATP), irreversible, carboxyl group transferred to biotin, then carboxyl group transferred from biotin to acetyl CoA
7 of 20
Describe the activation stage
Both malonyl CoA and acetyl CoA bind to an acyl carrier protein (ACP) -M on site 1, A on site 2, binding to ACP results in formation of malonyl-ACP and acetyl-ACP, facilitated by transferase proteins
8 of 20
What does the binding to ACP allow?
It makes malonyl CoA and acetyl CoA available to the enzymes for fatty acid synthesis
9 of 20
What enzyme is fatty acid synthesis catalysed by?
Fatty acid synthase (FAS)
10 of 20
Describe FAS in prokaryotes
Complex protein of distinct enzymes & contains all enzymes required
11 of 20
Describe FAS in eukaryotes
Single protein with multiple active sites, incorporates all activities needed (multifunctional enzyme)
12 of 20
What are the four stages of every cycle in the malonyl pathway?
Condensation, reduction (NADPH+H as hydrogen donor), dehydration, reduction (NADPH+H is the donor)
13 of 20
Where does the NADPH+H hydrogen donors come from?
The pentose phosphate pathway
14 of 20
Condensation reaction
Malonyl CoA looses carbon from CO2 and the carbon is replaced by the acetyl group from the acetyl CoA, (Enzyme: Condensing enzyme, KS), irreversible
15 of 20
First reduction reaction
Uses 1 NADPH+H as hydrogen donor, the B(3) carbon accepts both hydrogens, (Enzyme: 3-ketoacyl ACP reductase)
16 of 20
Dehydration reaction
Removes -OH from B(3) carbon and H from the a(2) carbon, (Enzyme: 3-hydroayacyl ACP dehydratase)
17 of 20
Second reduction reaction
Uses 1 NADPH+H as hydrogen donor, formation of fatty acyl ACP 2C atoms longer the acetyl ACP, (Enzyme: Enoyl ACP reductase)
18 of 20
What has happened after 1 round of the malonyl pathway?
It has used a malonyl ACP, an acetyl ACP and 2 NADPH+H, produced a fatty acyl 2 carbons longer than acetyl ACP, the fatty ACP is on site 1 of ACP
19 of 20
What needs to happen before the next cycle starts?
The 4-carbon fatty acyl is transferred to site 2 of ACP and a new malonyl group is attached to site 1
20 of 20

Other cards in this set

Card 2

Front

What does fatty acid synthesis require?

Back

CO2, co-factors (Biotin) and reducing power (NADPH)

Card 3

Front

What is the starting point for fatty acid synthesis?

Back

Preview of the front of card 3

Card 4

Front

What is the malonyl pathway?

Back

Preview of the front of card 4

Card 5

Front

How is acetyl CoA transported into the cytoplasm?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biochemistry resources »