Digestion and Absorption Flashcards
What is digestion?
the chemical and mechanical breakdown of ingested food into absorbable molecules
What is absorption?
movement of macronutrients, water, electrolytes from intestinal lumen into blood
What are the two pathways for absorption?
- transcellular
- paracellular
What is transcellular absorption?
cross luminal membrane via passive diffusion or transporters
What is paracellular absorption?
move across tight junctions between intestinal epithelial cells
What is the structure of intestinal mucosa?
- surface arranged in transverse folds
- villi line lumen of small intestine
The folds, villi, and microvilli of small intestine increase the surface area by how much?
600 fold
The surface of epithelial cells in the small intestinal lumen are line with microvilli, which is known as?
brush border
The villi of the small intestinal lumen are lined with what?
epithelial cells and goblet cells
Villi are longest in what section of small intestine?
duodenum
Villi are shortest in what section of small intestine?
ileum
What are the transverse folds of the small intestine?
folds of Kerckring with fingerlike villi
Give an example of monosaccharide.
glucose
Give an example of disaccharide.
sucrose
Give an eexample of polysaccharide.
amylose
What is the primary source of energy for most cells?
glucose
How is glucose supplied in diet?
- monosaccharides (simple sugars)
- disaccharides
- polysaccharides (complex chain of sugars)
All ingested carbohydrates must be digested to what for absorption by enterocytes?
monosaccharides
What enzymes are used for digestion of starch?
- alpha amylase
- glucoamylase
- alpha dextrinase
- maltase
- sucrase
- lactase
What are the monosaccharides for absorption?
- glucose
- galactose
- fructose
What are the brush border enzymes?
- sucrase
- lactase
- maltase
- alpha dextrinase
There are no mammalian enzymes to digest cellulose. What is used instead?
microbial enzymes
What transporter is used for glucose and galactose to get from intestinal lumen into enterocyte?
SGLT 1 (a Na+/glucose co-transporter)
What transporter is used for only fructose to get from intestinal lumen to enterocyte?
GLUT 5 (facilitated diffusion)
What transporter is used for glucose, galactose, and fructose to get from enterocyte into blood?
GLUT 2 (facilitated diffusion)
What enzyme will cleave bonds of oligosaccharides released from starch?
alpha dextrinase
A disorder characterized by failure to digest carbohydrates to absorbable form will cause what?
carbohydrates will remain in lumen and “hold” water to remain isosmotic which leads to osmotic diarrhea
Lactose intolerance is caused by what?
lactase deficiency
Lactose intolerance leads to what?
osmotic diarrhea
Which species have a natural diet high in cellulose, a complex polysaccharide?
- horses
- cattle
- sheep
Which species are usually fed diets high in grain (starch)?
- chickens
- pigs
Which species are omnivores and do well on diets of starch and soluble fiber?
- dogs
Which species is usually fed some starch in pet food diets but is naturally on a prey diet?
- cats
How many essential amino acids are there?
10
List the 10 essential amino acids. (Hint: PVT TIM HALL)
- phenylanine
- valine
- threonine
- tryptophan
- isoleucine
- methionine
- histidine
- arginine
- leucine
- lysine
Amino acids are usually provided in what form?
protein
Proteins must be digested to absorable forms via what enzymes?
proteases
What is the absorbable form of proteins?
amino acids and short peptides