digestion Flashcards
digestion
breakdown of complex molecules into simple molecules
absorption
transporting simple molecules across intestinal epithelium
in order for nutrients to be absorbed in SI much be transported across apical (ie luminal) surface of
enterocytes
then across basolateral surface of cell
apical (luminal) surface of enterocytes covered in
microvilli
before nutrients can reach the apical surface of enterocytes of SI, what do they have to diffuse through
glycocalyx; jelly-like layer of glycoprotein
what is attached to microvilli of enterocytes
digestive enzymes and proteins; project into glycocalyx
goblet cells between enterocytes produce
mucous
fluid flows slower where
closer to intestinal surface; ie unstirred water layer (think like a river, faster in middle, slower at banks)
what is the diffusion barrier nutrients must pass through before getting absorbed
unstirred water layer, mucous and glycocalyx
why is physical digestion (breakdown of particle size) important
- allows food to pass through GI tract
- increases SA exposed to digestive enzymes
what does physical digestion begin and end
mastication
ends in distal stomach by grinding action near pylorus (aided by breakdown of connective tissue by HCl and pepsin)
chemical digestion of each major nutrient is achieved through the process of
hydrolysis; splitting of a chemical bond by the insertion of a water molecule
what bond is hydrolyzed in digestion of carbs
glycosidic bond
what bond is hydrolyzed in digestion of proteins
peptide bond