Lipid Formation Flashcards
What is lipogenesis?
The formation of lipids from acetyl-CoA.
Where does lipogenesis take place?
Cytoplasm of the cell.
Which enzymes are used in lipogenesis?
Fatty acid synthase - a homodimer of 2 polypeptide chains and 7 enzymes.
What are the 3 stages of lipogenesis?
Activation, elongation, termination.
What is the reducing agent of lipogenesis?
NADPH.
At what stage does lipogenesis of a fatty acid stop?
At the 16 carbon stage, when palmitic acid is formed.
How does acetyl-CoA get into the cytoplasm for lipogenesis?
It reacts with oxaloacetate, forming citrate and CoA. Citrate can enter the cytoplasm, where it’s converted back to acetyl-CoA and oxaloacetate.
What is the activation step of lipogenesis?
Acetyl CoA + CO2 —> malonyl-CoA.
Uses ATP, catalysed by acetyl-CoA carboxylase.
What is the elongation step of lipogenesis?
Catalysed by fatty acid synthase. 2 carbons are added to fatty acid at a time, from malonyl-CoA.
What is the termination step of lipogenesis?
Palmitic acid is activated to palmitoyl-CoA - fatty acid may then be used to elongate further or to form double carbon bonds.
What is fatty acid elongase used for?
Allows palmitoyl-CoA to elongate in the endoplasmic reticulum.
What are desaturase enzymes used for?
Allows double bonds to be added to fatty acid chain in the endoplasmic reticulum.
What is the structure of cholesterol?
A 4 ring structure, made of 27 carbons.
How is cholesterol synthesised?
Synthesised from acetyl-CoA using HMG-CoA reductase.
How do statins reduce cholesterol?
They inhibit HMG-CoA reductase, causing liver cells to draw cholesterol out of circulation and reduce circulating cholesterol levels.
