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Small Intestine - Anatomy & Physiology (view source)
Revision as of 16:27, 22 July 2008
, 16:27, 22 July 2008→Triacylglycerol Digestion and Absorption
====Triacylglycerol Digestion and Absorption====
====Triacylglycerol Digestion and Absorption====
*Triacylglycerols (TAGs) are digested by lipases.
*Triacylglycerols (TAGs) are digested by lipases.
*TAG digestion begins in the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]], where lingual lipase is secreted in the saliva. It removes a fatty acid from the 3 position on the glycerol molecule producing 1,2-diacylglycerol(1,2 DAG) and a free fatty acid.
*TAG digestion begins in the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]], where lingual lipase is secreted in the [[Oral Cavity - Salivary Glands - Anatomy & Physiology|saliva]]. It removes a fatty acid from the 3 position on the glycerol molecule producing 1,2-diacylglycerol(1,2 DAG) and a free fatty acid.
*TAG digestion continues in the small intestine, with pancreatic lipase and bile from the liver. Pancreatic lipase is water soluble and the TAG and 1,2-DAG are lipid soluble. Bile creates an interface for the enzyme to digest the lipid molecules. Bile also emulsifies fats; it reduces the size of lipid droplets increasing the surface area available for digestion.
*TAG digestion continues in the small intestine, with pancreatic lipase and bile from the [[Liver - Anatomy & Physiology|liver]]. Pancreatic lipase is water soluble and the TAG and 1,2-DAG are lipid soluble. Bile creates an interface for the enzyme to digest the lipid molecules. Bile also emulsifies fats; it reduces the size of lipid droplets increasing the surface area available for digestion.
*Pancreatic lipase removes any further fatty acids from the 3 position and then from the 1 position to produce 2-monoacylglycerol (2-MAG) and a fatty acid.
*Pancreatic lipase removes any further fatty acids from the 3 position and then from the 1 position to produce 2-monoacylglycerol (2-MAG) and a fatty acid.
**Pancreatic lipase is unable to remove the fatty acid from the 2 position, so an enzyme called '''isomerase''' transfers the fatty acid from the 2 postion to the 1 postion to produce 1-monoacylglycerol (1-MAG).
**Pancreatic lipase is unable to remove the fatty acid from the 2 position, so an enzyme called '''isomerase''' transfers the fatty acid from the 2 postion to the 1 postion to produce 1-monoacylglycerol (1-MAG).
***Chylomicrons are too large to enter the capillaries but instead enter the lymph to eventually join the blood via the thoracic duct.
***Chylomicrons are too large to enter the capillaries but instead enter the lymph to eventually join the blood via the thoracic duct.
***This enables the lipid soluble TAG to be transported in the blood.
***This enables the lipid soluble TAG to be transported in the blood.
====Protein Digestion and Absorption====
====Protein Digestion and Absorption====
*Protein digestion begins in the [[Forestomach - Anatomy & Physiology|stomach]] where pepsin is secreted as a zymogen, pepsinogen. Pepsin is an endopeptidase and produces smaller polypeptides.
*Protein digestion begins in the [[Forestomach - Anatomy & Physiology|stomach]] where pepsin is secreted as a zymogen, pepsinogen. Pepsin is an endopeptidase and produces smaller polypeptides.