Digestion 3

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4/7/2013 1 Buffers Secreted in the mouth (salivary glands) and by the pancreas When food comes through the duodenum the pancreas will squirt in a very alkaline buffer solution. Buffers acid coming from the stomach. A lot of enzymes that will only work at a specific pH.

Endocrine vs. Exocrine Glands:

4/7/2013 2 Endocrine vs. Exocrine Glands Exocrine glands (ducted) Secrete directly into lumen (center) of canal Action takes place in lumen Examples Salivary glands Action in mouth Parotid glands Endocrine glands (ductless) Hormones Gastrin Secretin Enterogasterone Cholecystokinin

Pancreatic Acinar Cells:

4/7/2013 3 Pancreatic Acinar Cells Zymogens = proteases trypsinogen chymotrypsinogen procarboxypeptidase Other enzymes amylase digests starch lipase digests fats ribonuclease and deoxyribonuclease digest RNA and DNA

Intestinal Events Digestion:

4/7/2013 4 Intestinal Events Digestion Digestion All the final steps occur in small intestine Proteins to amino acids Fats to fatty acids and glycerol Carbohydrates to hexoses That doesn’t mean all the proteins, fats, and carbohydrates are broken down. There is still digestion in the colon.

Activation of Zymogens:

4/7/2013 5 Activation of Zymogens Trypsinogen converted to trypsin by intestinal epithelium Trypsin converts other 2 as well as digests dietary protein

Protein Digestion & Absorption:

4/7/2013 6 Protein Digestion & Absorption Brush border enzymes finish the task producing amino acids that are absorbed into the intestinal epithelial cells amino acid cotransporters move into epithelial cells & facilitated diffusion moves amino acids out into the blood stream Infants absorb proteins by pinocytosis (maternal IgA)

Carbohydrate Absorption:

4/7/2013 7 Carbohydrate Absorption Sodium-glucose transport proteins (SGLT) in membrane help absorb glucose & galactose Fructose absorbed by facilitated diffusion then converted to glucose inside the cell Liver

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