Absorption

Question 1

what is the main site of absorption?

Answer 1

duodenum + jejunum

Question 2

what is absorbed in ileum?

Answer 2

vitamin B12 and bile salts

Question 3

what is absorbed in the colon?

Answer 3

some Na+ and H2O, short chain fatty acids

Question 4

why is the small intestine suited to absorption?

Answer 4

• folds in wall
• villi
• microvilli
• rich blood supply
• lacteals
• polarised expression of transport proteins

Question 5

how is glucose absorbed?

Answer 5

glucose enters the cell via SGLT1, it then accumulates inside the cell which generates a gradient that allows glucose to leave via GLUT2

Question 6

what is glucose galactose malabsorption syndrome?

Answer 6

SGLT1 gene is mutated so no glucose absorption takes place

Question 7

what transporter does ACE inhibitor use?

Answer 7

PepT1

Question 8

what is a peptidomimetic drug?

Answer 8

drug designed to mimic a peptide

Question 9

how are labile drugs administered?

Answer 9

sublingually or rectally

Question 10

why are labile drugs administered the way they are?

Answer 10

they avoid the hepatic portal vein; they are not subject to first pass metabolism by liver. This means the concentration of the drug is not greatly reduced before systemic circulation

Question 11

venous blood from mouth and rectum does not go via _____

Answer 11

liver

Question 12

outline the steps in fat digestion

Answer 12

1. Emulsification of large fat droplets; increase surface area for action of lipase
2. Formation of mixed micelles; stabilises products of TG hydrolysis
3. MG and FA are transported with bile salts as micelles to apical membrane
4. Simple diffusion of MG and FA to intestinal epithelium
5. MG and FA enter endoplasmic reticulum where they are reesterified to form TG, coated w/ proteins to form chylomicrons, enter lacteals.
6. Recycling of bile salts

Question 13

pancreatic lipase is hydro____

Answer 13

philic

Question 14

what are chylomicrons?

Answer 14

lipoproteins that facilitate transport of lipis in the circulation. They’re released by exocytosis at the basolateral surface of the enterocytes. Chylomicrons deliver absorbed TAG to body’s cells.

Question 15

where is most water absorbed?

Answer 15

small intestine

Question 16

what is the proposed way in which H2O is absorbed?

Answer 16

paracellular pathway, SGLT1

Question 17

which vitamins are absorbed via diffusion?

Answer 17

fat soluble: A D E K

Question 18

how are vitamins B and C absorbed?

Answer 18

water soluble; mostly carrier mediated, but B12 is absorbed via endocytosis

Question 19

how are divalent ions absorbed?

Answer 19

carrier mediated

Question 20

what are the functions of saliva?

Answer 20

• lubrication
• solvent
• protection of teeth and gums

Question 21

what are the 3 salivary glands?

Answer 21

• parotid
• sublingual
• submandibular

Question 22

what is the function of HCl?

Answer 22

kill microbes

solubilisation

Question 23

how is pepsinogen converted to pepsin?

Answer 23

by Hcl

Question 24

acid secretion is stimulated by what?

Answer 24

• ACh,
• Gastrin
• Histamine

Question 25

basal secretion of HCl is __% the max rate

Answer 25

10%

Question 26

Outline the mechanism of acid secretion

Answer 26

1. H+ is generated within the parietal cell from dissociation of water. OH- formed in this process rapidly combine with CO2 to form HCO3- ions.
2. HCO3- is transported out of the basolateral membrane in exchange for Cl-. The effluc of HCO3- into blood results in a slight elevation of blood pH known as “alkaline tide”. This process serves to maintain intracellular pH in the parietal cell.
3. Cl- and K+ are transported into lumen of gastric pit by conductance channels and such is necessary for secretion of acid.
4. H+ is pumped out of the cell, into the lumen, in exchange for K+ through action of ATPase; K+ is effectively recycled.
5. Accumulation of osmotically active H+ in gastric pit generates an osmotic gradient across the membrane that results in outward diffusion of water.