Digestion of Carbohydrate and Proteins

Question 1

Define digestion

Answer 1

enzymatic conversion of complex dietary substances to a form that can be absorbed

Question 2

Luminal Digestion

Answer 2

digestion by pancreatic enzymes secreted in duodenum

Question 3

Membrane Digestion

Answer 3

digestion by enzymes situated at brush border of epithelial cells

Question 4

Where are products of digestion transported

Answer 4

across the apical and basolateral membraness

Question 5

what are digestable carbohydrates converted to

Answer 5

converted to monosaccharides for digestion

Question 6

explain the breakdown from glycogen or starch

Answer 6

broken down by alpha amylases to oligiosaccharides e.g. sucrose and lactose
broken down by oligiosaccharides to monosaccharides e.g. glucose and fructose

Question 7

what can alpha amylase break

Answer 7

only break internal a-1,4 linkages

Question 8

Where does Absorption of Final Products of Carbohydrate Digestion occur

Answer 8

Duodenum or jejunum

Question 9

Glucose and Galactose enter via

Answer 9

SGLT1

Question 10

Fructose enters via

Answer 10

GLUT5

Question 11

How do monosaccharides exit

Answer 11

GLUT2

Question 12

explain the mechanism of SLGT1

Answer 12

2 Na+ bind
Increases affinity for glucose to bind
Glucose then binds
2Na+ and glucose translocate from extracellualr to intracellular 
2 Na+ dissociate
Glucose affinity decreases
Glucose dissociates 
Cycle is repeated

Question 13

where is protein digested

Answer 13

in the stomach

Question 14

explain protein digestion in the stomach

Answer 14

HCL causes pepsinogen to be activated to pepsin which causes proteins to be broken down in to large amino acids

Question 15

after the protein digestion in the stomach what part of the GI tract is next responsible

Answer 15

duodenum - 1st part of the small intestine

Question 16

what happens in the duodenum

Answer 16

pancreas provides digestive enzymes via acinar cells as zymogens
when in the duodenum become activated
pepsinogen –> pepsin when activated by enteropeptidase
pepsin is also autocatalytic
chymotrypsinogen –> chymotrypsin
activated by pepsin
both of these break down AA chains from amino end
pepsin also activates carboxypeptdidase from decarboxypeptidase
carboxypeptidase breaks the AA chain from the carboxyl end

Question 17

What are small polpypeptides broken down by

Answer 17

brush border enzymes

Question 18

Amino Acids are brought into the enterocyte and then into the blood by what mechanisms

Answer 18

5 Na+ dependent and 2 Na+ co-transporters

Question 19

Di, tri and tetra peptides are brought into the enterocyte and then into the blood by what mechanisms

Answer 19

H dependent mechanisms at brush border where they are further hydrolysed to AA in enterocyte via pepsin