Lipogenesis

What is lipogenesis?

The formation of fat from simple sugars converted to fatty acids and then esterified with glycerol to form TAG.

Where does lipogenesis primarily occur?

In the cytoplasm of the liver.

What is the major source for fatty acid synthesis?

Glucose.

What process initiates de novo synthesis of fatty acids?

The transfer of acetate units from mitochondrial acetyl-CoA to the cytosol.

What is the rate-limiting step in fatty acid synthesis?

The carboxylation of acetyl-CoA to form malonyl-CoA.

Which enzyme converts acetyl-CoA to malonyl-CoA?

Acetyl-CoA Carboxylase (ACC).

What are the main sources of NADPH required for fatty acid synthesis?

The Pentose Phosphate Pathway (PPP) and the cytosolic conversion of malate to pyruvate.

What is the primary end product of fatty acid synthesis?

Palmitic acid (C16:0).

How is fatty acid synthesis regulated?

By hormones such as insulin (which stimulates synthesis) and glucagon (which inhibits it).

What occurs during the process of fatty acid desaturation?

Long-chain fatty acids are desaturated to introduce cis double bonds, requiring NADH and specific desaturases.

What happens to VLDL after being released into the bloodstream?

It is converted to IDL and then either returned to the liver or converted to LDL which delivers cholesterol to tissues.

What role does lipoprotein lipase (LPL) play in lipid metabolism?

It breaks down triglycerides in VLDL and chylomicrons into free fatty acids.

What is the primary function of TAG synthesis in the body?

To store fats derived from excess carbohydrates and proteins.

What is a significant pathway for synthesizing glycerol phosphate in adipose tissue?

From dihydroxyacetone phosphate (DHAP), as glycerol kinase is not expressed.

What are the sources of free fatty acids for energy during lipid metabolism?

Fatty acids are released from triglycerides in lipoproteins and used by muscles for energy.

Which types of lipids are synthesized in the liver from excess calories?

Triacylglycerols (TAGs) and phospholipids.

How are dietary triglycerides absorbed and utilized?

They are broken down into free fatty acids and 2-monoglycerides in the small intestine, then reassembled into triglycerides in enterocytes.