lipogenesis Flashcards
(32 cards)
What is lipogenesis?
Lipogenesis is the biosynthesis of various forms of lipids in the human body.
When does lipogenesis occur?
Lipogenesis occurs in a well-fed condition when there is an excess of glucose after meals.
What promotes lipogenesis?
Insulin promotes lipogenesis.
Where does lipogenesis primarily take place?
Lipogenesis primarily takes place in the cytoplasm of the liver.
What other tissues are involved in lipogenesis?
Other tissues involved in lipogenesis include the intestine and mammary glands.
Why does lipogenesis occur?
Excess glucose cannot be stored as it is in the body; it is first converted to glycogen, but glycogen storage is limited.
What happens to excess glucose once glycogen stores are full?
Excess glucose is oxidised to pyruvate through glycolysis, and further to acetyl-CoA via the PDH complex reaction.
What is formed from excess acetyl-CoA during lipogenesis?
Excess acetyl-CoA is diverted for lipogenesis to form fatty acids, which are stored as triacylglycerol (TAG) in adipose tissue.
What is de novo biosynthesis of fatty acids?
De novo biosynthesis of fatty acids is a reductive biosynthetic mechanism that uses simple carbon units (acetyl-CoA) and reducing equivalents like NADPH+H+ to form long-chain fatty acids.
Where does de novo biosynthesis of fatty acids mainly occur?
It mainly occurs in the cytosol of the liver, adipose tissue, intestine, lungs, brain, renal cortex, and mammary glands during lactation.
What can the fatty acids produced be used to biosynthesise?
The fatty acids produced can be used to biosynthesise triacylglycerol, phospholipids, glycolipids, and cholesterol esters.
What is a common fatty acid produced through de novo biosynthesis?
Palmitic acid (C16) is a common fatty acid produced through de novo biosynthesis.
How many molecules of acetyl-CoA are required for the biosynthesis of palmitic acid?
Its biosynthesis requires eight molecules of acetyl-CoA.
What is the source of acetyl-CoA for palmitic acid biosynthesis?
The source of acetyl-CoA is excess glucose.
What is the fatty acid synthase (FAS) complex?
The fatty acid synthase (FAS) complex is a multi-enzyme complex responsible for the de novo biosynthesis of fatty acids.
What is the structure of the FAS complex?
It is a homodimer with two identical subunits linked in a head-to-tail fashion.
What does each subunit of the FAS complex contain?
Each subunit contains eight components, including seven enzymes and one protein.
What is the role of acyl carrier protein (ACP) in the FAS complex?
ACP acts as a carrier of the growing acyl chain during fatty acid biosynthesis.
What is the prosthetic group of ACP derived from?
ACP has a 4-phosphopantetheine prosthetic group derived from vitamin B5.
What are the three stages of de novo biosynthesis of fatty acids?
- Translocation of acetyl-CoA from mitochondria to cytosol. 2. Carboxylation of acetyl-CoA to malonyl-CoA. 3. Reactions of the FAS complex.
What occurs in Stage I of fatty acid biosynthesis?
Mitochondrial acetyl-CoA is converted to citrate, transported to the cytosol, and then cleaved to release acetyl-CoA.
What occurs in Stage II of fatty acid biosynthesis?
Acetyl-CoA is carboxylated to malonyl-CoA by acetyl-CoA carboxylase (ACC) in the presence of biotin and ATP.
What occurs in Stage III of fatty acid biosynthesis?
A series of reactions that use acetyl-CoA and malonyl-CoA to synthesise fatty acids.
What regulates fatty acid biosynthesis?
Regulation occurs through nutritional status and hormonal influences.
