Lipid Digestion Flashcards
Does lipid digestion (TAGs) occur in the mouth? Explain why/why not.
The water-soluble enzymes do not breakdown the non-polar fat and oil in the mouth.
However, the mouth contains a small amount of lingual lipase (non-polar enzyme) that does breakdown some of the ester connections within the triacylglycerol (TAG).
What role(s) does the stomach play in lipid digestion? Are any enzymes present? If so what do the enzymes do?
Once the fat/oil enters the stomach it separates into smaller droplets within the chyme, which makes the fat/oil easier to digest.
The stomach also contains gastric lipase enzymes, which can break some of the ester bonds within TAG.
However, most of the breakdown of TAG occurs in the small intestine.
How do the pancreatic lipases convert TAG into MAG and fatty acids in the small intestine? Explain how the monoacylglycerol (MAG) and fatty acids are used to generate micelle’s.
The pancreatic lipase enzymes break down TAG into MAG and two fatty acids (in the small intestine), by cutting two of the ester connections between the glycerol and the fatty acids (within TAG).
The MAG and fatty acids then associate together to form spherical micelle structures, which have a polar outer shell (glycerol and carboxylic acid group in the fatty acid) and a non-polar centre (fatty acid tails).
Once the micelles are absorbed into the intestinal cells they require repackaging. What role do the micelles have in creating the chylomicrons (deliver TAG into the bloodstream)?
Once inside the intestine cells, the micelles are broken down into the MAG and fatty acid components.
Ester bonds are formed to link the MAGs to the fatty acids in order to create TAG.
Many TAGs combine with protein, cholesterol and phospholipids to form chylomicrons, which are carried into the bloodstream via the lymphatic system.
Once in the bloodstream, the chylomicron releases the TAG which is either stored or metabolized.
A) Discuss how and under what circumstances the TAG would be stored
B) Discuss how and under what circumstances TAG would be metabolised.
When TAG is not required to generate ATP (energy needs of the body have been met), the TAG will be transported to an adipocyte (within the adipose tissue) to be stored as fat.
B) When TAG is required to generate ATP the TAG is broken down into fatty acids and glycerol by lipoprotein lipases. Once inside the cell, the fatty acids
and glycerol are metabolized to generate ATP via the relevant various metabolic reactions.
What is the starting input for beta-oxidation and what is the final output?
Fatty acids (specifically acyl CoA) are the input required for beta-oxidation to begin.
The most important output of beta-oxidation is acetyl CoA and the reduced coenzymes FADH2 and NADH.
1 NADH,
1 FADH2
1 acetyl CoA
