Digestion-Review

Question 1

What kind of enzymes are found in the lumen? on the mucosal surface/brush border?

Answer 1

lumen: lipases, pancreatic enzymes (dumped there), pepsin
mucosal surface/brush border: enzymes for things that are almost ready to absorb (disaccharidases, enterokinase, etc.)

Question 2

hella generally, describe digestion and absorption of carbohydrates

Answer 2

amylase breaks down starches into polysaccharides, then to oligo, then to di, then to monsaccharides that can be absorbed; each polysaccharide has its own enzyme

Question 3

hella generally, describe digestion and absorption of proteins; give one big difference from CHO

Answer 3

enzymes break proteins into peptides; peptides are either broken to free amino acids (50%, absorbed) or di or tri peptides (50%, ALSO absorbed, difference from CHO where only mono form can be absorbed)

Question 4

describe 2 important enzymes in protein digestion

Answer 4

trypsin: once activated, activates everyone else
pepsinogen: from stomach, begins protein breakdown before SI

Question 5

what are the 4 main steps to digestion/absorption of fat?

Answer 5

1. emulsification
2. hydrolysis
3. micelle formation
4. absorption

Question 6

generally describe digestion and absorption of fat

Answer 6

1. fat is mixed in the stomach to a fat slurry
2. bile acts as a detergent to emulsify fay
3. lipase and colipase break fat down into smaller and smaller particles until eventually we produce the micelle
4. micelles are absorbed into enterocytes either passively or actively via fatty acid binding proteins (the bile is then absorbed in the ileum bc no longer needed)
5. micelles become chylomicrons in enterocytes, where they are repackaged into triglycerides, have specific proteins added, have phospolipids and other fats until actually become that chylomicron
6. the water-soluble chylomicron is transported through the central lacteal to the thoracic duct and then enters circulation to provide fats to tissues