Lipid Metabolism Flashcards
How much of dietary fats do TAGs constitute?
90%, being manor form of metabolic energy storage.
What do TAGs consist of?
Glycerol backbone and a trimester of fatty acids.
Why does lipid digestion take place at the water-lipid interface?
Because TAGs are water insoluble yet their enzymes are water soluble.
What is rate of lipid digestion dependent on?
Surface area of the water-lipid interface.
What increases rate of lipid digestion?
Churning peristaltic movements of the intestine, and emulsifying action of bile acids.
Bile Acids
Amphiohatic detergent like molecules that solubulise fat globules.
Where do Bile Acids come from?
Synth in the liver from cholesterol, secreted as glycine or taurine conjugates into the gall bladder for storage.
Where on TAGs does hydrolysis occur?
1 and 3 alpha carbon by lipases.
Where on TAGS does lipase hydrolysis take place?
1 and 3 alpha carbon
What does lipase TAG hydrolysis form?
1,2 diacylglycerols and 2-acylglycerols.
Interfacial Activation
The increase of lipase activity at lipid-water interface.
What is Lipase dependent on for binding to the LW interface?
Mixed micelles of phosphatidylcholine and bile acids and pancreatic colipase.
What is the process if interfacial Activation?
The lipase active site within its NTD contains a catalytic domain: this is covered by a 25 residue helical lid in the absence of micelles, of which remove this lid through CC, revealing a expansion hole, generating a hydrophobic surface at the active site.
What does colipase do proceeding interfacial activation?
Colipase binds CTD of lipase, in a way the hydrophobic tips of its three loops extend from the complex, creating a continuous hydrophobic plateau, assisting in binding complex to lipid surfaces.
Where does lipid absorption take place?
Cells lining the small intestine of the fatty acid and glycerol products.
When does lipid digestion take place?
Proceeding intestinal metabolism.
How do Bile Acids play roles in lipid digestion?
Permit transport of non polar lipid degraded products across the intestinal wall.
What do FA form upon absorption?
Complexes with Intestinal Fatty Acid Binding Protein in the cytoplasm.
Why does FA need to bind IFABP?
It increases FA solubility.
Intestinal Fatty Acid Binding Protein
This coordinates lipid transport and metabolism.
What is the structure of IFABP?
10 antiparralel beta pleated sheets, between of which the fatty Cids occupy parallel to the strands.
What happens to FA after Binding IFABP?
Transport to other tissues for metabolism or storage in the form of lipoproteins.
Lipoproteins
Globular, micelles like particles consisting of a non polar core of TAGS, surrounded by an amphiphilic coating of proteins, phospholipids and cholesterol.
What upon absorption are FA packaged into?
Lipoproteins called Chylomicrons
