Physiology - GI

Question 1

What do gastric secretions contain?

Answer 1

HCl, pepsin, mucous, water

Question 2

What does water do to bolus

Answer 2

turns it into chyme

liquidy consistency

Question 3

What are the 3 structures that make up the SI?

Answer 3

duodenum, jejunum and ileum

Question 4

What is digestion?

Answer 4

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

Question 5

What are the 2 commonly digestive processes in the SI, and which enzymes is it mediated by?

Answer 5

luminal - pancreatic enzymes secreted into duodenum
membrane - enzymes situated at the brish border of epithelial cells

Question 6

What are enterocytes?

Answer 6

Type of epithelial cells that lines the inner surface of the SI

- have microvilli on their surface + imp role in absorption of nutrients

Question 7

Absorption

Answer 7

process by which absorbabl products of digestion are transferred across apical + basolateral membranes of enterocytes

Question 8

General mechanism of digestion + absorption

What requires no breakdown in digestion

Answer 8

glucose

Question 9

Eg of molecule that undergoes luminal hydrolysis of polymer to monomer

Answer 9

proteins –> AA

Question 10

Eg of molecule that undergoesbrushborder hydrolysis

Answer 10

oligomer to monomer

Question 11

Eg of molecule that undergoes** intracellular hydrolysis**

Answer 11

peptide breaksdown to AA intracellularly

Question 12

Eg of molecule that undergoes luminal hydrolysis + intracellular resynthesis

Answer 12

triacylglycerol -> glycerol + fatty acids -> triacylglycerol

Question 13

properties of amylose

Answer 13

• polysaccharide
• straight chain
• a-1,4 linkages

Question 14

properties of amylopectin

Answer 14

• polysacccharide
• branched
• a-1,4 and a-1,6 linkages

Question 15

properties of glycogen

Answer 15

• polysaccharide
• brandched
• a-1,4 and a-1,6 linkages

Question 16

linkage in sucrose

Answer 16

glucose + fructose a-1,2 linkage

Question 17

linkage in lactose

Answer 17

glucose + galactose b-1,4 linkage

Question 18

Where is a amylase produced?

Answer 18

salivary glands + pancreas

Question 19

What is the role of alpha amylase?

Answer 19

• break down of internal alpha 1,4 linkages but not terminal alpha 1,4 linkages

Question 20

What can alpha amylase not cleave?

Answer 20

• cannot cleave alpha 1,6 linkages at branch points in amylopectin or 1,4 linkages adjacent to branch points

Question 21

What are the products of alpha amylase?

Answer 21

linear glucose oligomers (maltotriose + maltose) and alpha limit dextrins

Question 22

Oligosaccharides are __________ proteins with a ____ domain that faces the ____ of the GI tract

Answer 22

integral membrane, catalytic, lumen

Question 23

What linkage is cleaved by oligosaccharidases in maltose, maltoriose and alpha limit dextrins to yield glucose

Answer 23

alpha 1,4 linkages

Question 24

What degrades the alpha 1,4 linkages in straight chain oligomers (up to 9 monomers in length)?

Answer 24

maltase

Question 25

role of sucrase

Answer 25

hydrolyses sucrose to glucose and fructose

Question 26

role of **isomaltase**

Answer 26

only enzyme that splits the branching of a-1,6 linkages of alpha limit dextrins

Question 27

**glucose and galactose absorbed by what transportoe?**

Answer 27

SGLT1 - secondary active transport mediated

Question 28

**fructose is absorbed by what?**

Answer 28

GLUT5 - via facilitated diffusion

Question 29

**exit of all monosaccharides is mediated by what?**

Answer 29

facilitated diffusion - GLUT2

Question 30

What criteria's must be met for substrate to be transported via SGLT1?

Answer 30

1. hexose in **d conformation** 2. one that can form a pyranose ring

Question 31

What is the mode of operation of SGLT1?

Question 32

In general, pepsin cleaves what to what

Answer 32

proteins into peptides | not imp for protein digestion

Question 33

is pepsin an endo- or exopeptidase?

Answer 33

endo

Question 34

What are the 5 pancreatic proteases?

Answer 34

- elastase (endo) --> oligopeptides - trypsin (endo) --> oligopeptides - chymotrypsin (endo) --> oligopeptides - carboxypeptidase A (exo) --> single AA - carboxypeptidase B (exo) --> single AA

Question 35

brush border peptidases

Answer 35

numerous, have affinity for larger oligopeptides, either endo/ exopeptidases

Question 36

cytoplasmic peptidases primarily hydrolyse what?

Answer 36

dipeptides + tripeptides