9. Digestion and Absorption of Protein and Carbohydrates Flashcards
Where are the principle sites for protein digestion?
Stomach
Small intestine
What digestion of protein occurs in the mouth?
Chewing
Saliva aids swallowing
What type of cells release pepsinogen in the stomach?
Chief cells
What type of an enzyme is pepsin?
Endopeptidase
What converts pepsinogen to pepsin?
HCl
What are the two major pancreatic enzymes in protein digestion?
Chymotrypsin
Trypsin
What converts trypsinogen to trypsin?
Enteropeptidase
What converts chymotrypsinogen, proelastase and procarboxypeptidase to their active forms?
Trypsin
What types of enzymes are trypsin, chymotrypsin and elastase?
Endo-peptidase
MOA: Serine protease
What types of enzymes are carboxypeptidase A and B?
Carboxypeptidases
MOA: Metalloprotease (Zn++)
What types of bonds does trypsin cleave?
Adjacent to basic AAs
What types of bonds does chymotrypsin cleave?
Adjacent to hydrophobic AAs
What types of bonds does elastase cleave?
Adjacent to small AAs
What types of bonds does Carboxypeptidase A cleave?
Hydrophobic AAs at C-terminus
What types of bonds does Carboxypeptidase B cleave?
Basic AAs at C-terminus
What are the products of protein digestion?
Tetra-peptides
Tri-peptides
Amino acids
What are the principle sites of carbohydrate digestion?
Mouth
Intestinal lumen
What carbohydrate digestion occurs in the mouth?
Chewing
Salivary amylase hydrolyses random a(1>4) bonds
What pancreatic enzymes are involved in carbohydrate metabolism?
Endoglycosidases
Disaccharidases
Oligosaccharidases
What enzymes are used to breakdown maltose and maltotriose?
Glucoamylase, sucrase, maltase
What are the breakdown products of maltose, maltotriose and trehalose?
2 glucose
What breaks down sucrose?
Sucrase
What are the breakdown products of sucrose?
Glucose and fructose
What breaks down lactose?
Lactase
What are the breakdown products of lactose?
Glucose and galactose
What breaks down trehalose?
Trehalase
What is the cause of lactose intolerance?
Insufficient lactase
Undigested lactose builds up in the large intestine, and get digested by bacteria, which produce gases
Which enzymes are anchored to the microvilli?
Aminopeptidase Endopeptidase Carboxypeptidase Dipeptidase Disaccharidases Oligosaccharidases
What form is protein absorbed most rapidly?
Peptides
How are peptides absorbed into the enterocyte?
Coupled to a H+ gradient, which is maintained by a Na+/H+ exchanger
Metabolised into free AAs in the enterocyte, which can be absorbed into the blood
How is protein released into the interstitial fluid?
Facilitated diffusion
Co-transport
Glutamate and aspartate are used as energy and not transported out of enterocyte
Describe the transport of monosaccharides into and out of the enterocyte?
- Glucose and Na+ bind to SGLT on luminal membrane
- Na+ moves down electrochemical gradient
- Na/K exchanger pumps Na+ out of the cell
- GLUT transports glucose into interstitial fluid
