Triglyceride Metabolism and Lipogenesis

Flashcards to review the key concepts of triglyceride metabolism, fatty acids, and lipogenesis.

What are triglycerides (TAGs)?

Three fatty acid chains ester-linked to a glycerol backbone.

Describe the structure of fatty acids.

Long chains of 12-24 carbon hydrocarbons with a carboxylic acid group (COOH).

What determines the melting point of a fatty acid?

The number of double bonds; more double bonds result in a lower melting point.

What does the X in ‘omega X’ mean in terms of fatty acid nomenclature

X is the carbon number where the first double bond appears in the chain.

Why are omega-3 and omega-6 fatty acids considered essential?

Humans lack the desaturase enzymes to add double bonds lower than omega-9, so they must be obtained from the diet.

List three reasons why altering fatty acids is important in the body.

1. Membrane phospholipids composition,

2. Tissue-specific membrane compositions

3. Some fatty acids are precursors to signalling molecules.

Why must triglycerides be broken down before absorption?

Triglycerides are too large to be absorbed directly.

What enzyme facilitates the reaction of a free fatty acid with Co-enzyme A and ATP, and what products are formed?

Acyl CoA synthetase facilitates the reaction, forming Acyl-CoA, water, pyrophosphate, and AMP.

What is the role of acyltransferase in fatty acid uptake and storage?

It facilitates the reaction of two activated fatty acids with monoacylglycerol to form a triglyceride.

What is a lipoprotein?

A mixture of lipids and proteins, with a phospholipid and cholesterol outer layer, and a triglyceride and cholesterol inner core.

What are chylomicrons used for?

Transport of triglycerides and other lipids from the gut to tissues.

How do endothelial cells facilitate the uptake of fatty acids into adipose tissue?

Endothelial cells have lipoprotein lipase attached on the luminal side, which cleaves off fatty acids for cell entry

What happens to the chylomicron after it has offloaded most of its triglycerides?

It becomes a chylomicron remnant and is removed from circulation by the liver.

What is the role of the C2 protein on the chylomicron?

It attaches to the lipoprotein lipase, allowing the triglyceride to enter the active site of the enzyme.

Where does glycerol-3-phosphate come from during intestinal synthesis of triglycerides?

Dihydroxyacetone Phosphate (DHAP).

What enzyme moves the acyl from CoA onto glycerol-3-phosphate to form lysophosphatidic acid?

G-3-P acyltransferase.

What enzyme removes the phosphate from phosphatidic acid, converting it into diacylglycerol?

Phosphatidic acid phosphatase.

What is the final step in triacylglycerol synthesis?

Diacylglycerol acyltransferase moves an acyl group onto diacylglycerol to form triacylglycerol.

What enzyme is used to covert DHAP into G-3-P

G-3-P dehydrogenase