Gut Function (III) Flashcards
What are the 3 parts of the small intestine
Duodenum
Jejunum
Ileum
What lays on top of the muscle and mucosa layers on the small intestine
Large villi made up of one cell thick epithelial cells
What are the gaps in between villi called
Crypt
What types of cells cover the villi
Goblet cells and enterocytes(microvilli epithelium)
What is the apical membrane where microvilli are on enterocytes called
Brush border membrane
Which areas does digestion of carbs lipids and proteins take place
Lumen
Apical brush border membrane
Cytosol of enterocytes
Where does absorption take place eg of carbs lipids water naCl
At enterocytes
Where are secretions of fluid and naCl happening
Crypt
Which polysaccharides does amylase from liver work on
Glycogen and starch
What does amylase convert glycogen and starch into
Dextrins - short chains of glucose
Where are disaccharides broken down and which enzymes
Brush border membrane
Maltase, sucrase , lactase
After digestion by brush border membranes, what monosaccharides are absorbed into the blood down enterocytes
Galactose fructose and glucose
Why can amylase only convert starch and glycogen into disaccharides and not mono
Because amylase is an endo enzyme so can’t break external bonds
How do glucose and galactose get through the apical membrane
Na cotransporter
Higher na outside of the cells
What is the na glucose transporter called
SGLT1
How is the na removed out of the cell when cotransported in
K/na ATPase on baso lateral membrane
How does glucose and galactose and fructose get removed out the baso lateral membrane
Glut 2 (facilitated diffusion)
How is fructose transport into the apical membrane different
Facilitated diffusion via GLUT5
Exit via glut 2
What digests proteins in the lumen
Pancreatic and gastric proteases
Which gastric protease is an endopeptidase in lumen
Pepsin
Which pancreatic protease is both an endo and exo peptidase in lumen
Trypsin
What kind of enzymes are those in brush border and cytosol
Endo exo and dipeptidases
What gets absorbed if the epithelium isn’t leaky (proteins)
Peptides via AT
Amino acids via SAT
What allows for active transport of peptides into apical membrane
Low ph (high H) on outside
H is used for energy to carry peptides in to cytosol
What happens to the peptides in the cytosol
Broken down by the exo endo and dipeptidases
AA then FD out
How is the NA gradient outside used to move amino acids
Co transport SAT
What is the na amino acid co transporter called
Pep T1
How do amino acids cross the baso lateral membrane
Facilitated diffusion
How is the H gradient produced to transport peptides
Na/H exchanger (NHE3)
What happens first in lipid digestion
Emulsification by bile salts to increase SA for gastric and pancreatic lipase
Why is colipase needed for digestion of lipids
Stops bile acids inhibiting lipases working
What are lipids broken down into
Monoglycerides and 2 fatty acids
Which aggregate structure forms around the monoglycerides and fatty acids (hydrophilic glycerol protection)
Micelles
Other than monoglycerides and fa what else is there in micelles
Cholesterol
Lipid soluble vitamins eg a d e k
Bile salts
How do monoglycerides and fa get into enterocytes apical membrane
Passive diffusion (lipophillic)
How does cholesterol get transported into enterocytes
Carrier protein
Why can FA diffuse passively
Higher conc of free fa outside due to re esterification at the SER
What forms at the SER from the esterification of cholesterol monoglycerides and fa and proteins
Chylomicrons
How are chylomicrons transported into the lymph vessels
Golgi vesicles
