Digestion and Absorption

Question 1

Define digestion

Answer 1

the breakdown of nutrients into absorbable molecules

Question 2

Define absorption

Answer 2

the movement of nutrients, water and electrolytes from the gut lumen into the internal environment

Question 3

Features of small intestine structure for absorption

Answer 3

• surface of SI arranged in circular folds of Keckring
• vill project from these folds
• surface of villi covered in epithelial cells (enterocytes) with mucous secreting cells . Their apical surface covered by microvilli (brush border)

Question 4

what does carbohydrate digestion begin with

Answer 4

salivary alpha-amylase

Question 5

3 monosaccharides absorbed in the SI and transport

Answer 5

glucose (Na cotransporter SGLT1)
galactose (Na cotransporter SGLT1)
fructose (facilitated diffusion by GLUT5)

Question 6

digestible vs indigestible glucose

Answer 6

1,4 alpha glycosidic bond (starch and glycogen)

plant cellulose 1,4 BETA glycosidic bond

Question 7

two types of duodenal carbyhydrate enzymes AND what they do

Answer 7

pancreatic amylase (secreted from pancreas --> duodenum. digests internal alpha 1,4 glycosidic bonds. produces 3 things)
brush border enzymes (maltase, sucrase, lactase - act on disaccharides --> monosaccharides)

Question 8

what three things does pancreatic amylase produce

what happens to them

Answer 8

WE ARE TRYING TO GET TO MALTOSE

maltotriose
maltose
alpha-limit dextrin

these are digested by oligosaccharides (alpha-glucosidase and isomaltase)

Question 9

what does isomaltase do

Answer 9

cleaves alpha-1,6 glycosidic bonds in alpha-limit dextrin

Question 10

what action does maltase, sucrase and lactase do

Answer 10

Maltase digest alpha 1,4 glycosidic bond

sucrase digests alpha 1,2 glycosidic bond

Lactase digests beta 1,4 glycosidic bond

Question 11

what enzymes do we start and end with in protein digestion

Answer 11

stomach: pepsin
SI: pancreatic and brush border proteases

Question 12

action of trypsinogen

Answer 12

use enterokinase in brush border to activate into trypsin

this is required to activate endopeptidases and exopeptidases

Question 13

function of endopeptidases

Answer 13

cleave large polypeptides in middle of chain (oligopeptides)
eg. pepsin, trypsin, chymotrypsin, elastase

Question 14

function of exopeptidases

Answer 14

clease amino acids one at a time from either end of protein
eg. carboxypeptidase
aminopeptidase