Lectures 12 & 13 - Digestion & Absorption Flashcards
What is found in between the villi of the small intestine?
Crypts of Luberkuhn
What 4 digestive enzymes act on polypeptides?
- Gastric pepsins
- Pancreatic proteases
- Intestinal mucosal polypeptides
- Enterocyte cytoplasm peptidases (di and tripeptides only)
What are the 7 digestive enzymes secreted by the intestinal mucosa in the brush border membrane?
- Enterokinase
- Peptidases
- Maltase
- Isomaltase
- Lactase
- Sucrase
- Cystoplasm peptidases
What 2 digestive enzymes act on proteins? Products?
- Gastric pepsins
- Pancreatic proteases
Products: smaller peptide chains
Products of lipases?
Diglycerides, monoglycerides and FAs
Products of salivary and pancreatic amylases?
alpha-limit dextrins, maltotriose, and maltose
What is the activator of amylases?
Cl-
Products of enterocyte cytoplasm peptidases?
AAs
Products of brush border peptidases?
AAs, di and tripeptides
Forms of carbs ingested? Majority?
- Starch***
- Disaccharides***
- Fibers = cellulose
Does the small intestine have both villi and microvilli? Difference? Which make up the brush border?
YUP
Villi sit on folds and ***microvilli sit on the villi
What is the central lacteal covered by in the villi?
Capillary net
Where are the small intestinal villi located exactly?
From the major papilla in the duodenum through the ileum, although they are less dense in the distal areas
2 types of brush border enzymes?
- Proteases
2. Saccharidases
What are starches?
Polymers of glucose attached via alpha glycosidic bonds
What is sucrose?
Fructose + glucose
What is lactose?
Galactose + glucose
What is maltose?
Glucose + glucose
What is cellulose?
Polymers of glucose attached via beta glycosidic bonds
Do humans have cellulase?
NOPE
Can disaccharides be absorbed by the enterocytes?
NOPE
Describe the breakdown of starch.
- In the mouth digestion by salivary alpha-amylase into maltose oligosaccharides (and some isomaltose oligosaccharides)
- Majority of digestion occurs in the small intestines by pancreatic alpha amylase producing small glucose polymers (alpha-limit dextrins, maltotriose, maltose, sucrose, lactose)
- Final digestion done by brush border enzymes
In how much time are all polysaccharides digested in the small intestine?
Within 10-20 min (by the time the chyme reaches the upper jejunum)
What can maltase and isomaltase digest? Products?
Maltose and 3-9 glucose polymers
Products: glucose, maltose, and oligosaccharides