lecture 24 - glucose absorption

Question 1

SGLT =

Answer 1

sodium-dependent glucose transporter protein

Question 2

tight junctions divide cells into ?

Answer 2

apical and basolateral membrane domains

Question 3

how are the ion gradients necessary for glucose absorption set up?

Answer 3

Na⁺/K⁺ pump

Question 4

____ uses energy from Na+ gradient to actively accumulate glucose above its ________ ________

Answer 4

_SGLT_ uses energy from Na+ gradient to actively accumulate glucose above its _Concentration_ _gradient_

Question 5

glucose exits the cell facilitated by _____ transport proteins in the _______ membrane domain, by ________ ________

Answer 5

glucose exits the cell facilitated by _GLUT_ transport proteins in the _basolateral_ membrane domain, by _passive_ _diffusion_

Question 6

what happens to the Na+ which also enters the cell with glucose?

Answer 6

exits via basolateral Na-pump

Question 7

how is osmotic imbalance (due to glucose and Na+ and glucose moving across epithelium) equilibriated ?

Answer 7

paracellular Cl- (down electrical gradient) and water (concentration gradient) fluxes

Question 8

direction of transport through GLUT

Answer 8

either way, depends on concentration gradient

Question 9

oral rehydration therapy

Answer 9

exploits ability for glucose to increase Na+ absorption and hence Cl- and WATER

Question 10

dehydrated babies with diarrhoea given…

Answer 10

simple sugar solution to orally rehydrate them. responsible for saving millions of babies erry year

Question 11

glucose/galactose malabsorption syndrome caused by?

Answer 11

mutation causing gene 1 for glucose symporter, SGLT (in the small intestine), to be knocked-out

Question 12

consequence of glucose/galactose malabsorption syndrome

Answer 12

glucose/galactose accumulate in the lumen of the small intestine, therefore the osmotic imbalance causes water to enter the lumen - ending in watery chyme aka diarrhoea

Question 13

treatment of glucose/galactose malabsorption syndrome

Answer 13

• removal of glucose/galactose from diet - fructose used as carbohydrate source - fructose uses GLUT 5, a facilitative transporter specific to fructose

Question 14

how many litres of body fluid filtered by Kidneys per day?

Answer 14

180 litres per day

Question 15

what will happen if all the glucose filtered out of the blood isn’t reabsorbed?

Answer 15

glucose in urine. sweet piss.

Question 16

glucosuria =

Answer 16

glucose accumulating in the urine

Question 17

when does glucosuria occur?

Answer 17

when SGLT protein cannot absorb all the glucose fast enough because the transport maximum of SGLT is exceeded i.e. the renal threshold is surpassed

Question 18

most common cause of glucosuria

Answer 18

diabetes melitus, becuase blood sugar is too high (over 200mg/100mL) due to deficient insulin activity

Question 19

renal threshold =

Answer 19

~200mg/100mL blood plasma. this is the maximum that SGLT can deal with

Question 20

Which protein transports fructose?

Answer 20

GLUT 5

Question 21

which number shows…

• transport maximum
• renal threshold

Answer 21

1 = renal threshold

2 = transport maximum