Lecture 6 and 7

Question 1

In the absence of glucose, net sodium absorption…

Answer 1

decreases- this is the first bit of evidence to show a link between sodium and glucose absorption.

Question 2

What does DNP do?

Answer 2

Uncouples mitochondria so stops ATP production.

Question 3

What did DNP do to net sodium absorption?

Answer 3

Decreased it to nearly zero, showing that the sodium and glucose movement requires energy.

Question 4

What does ouabain do?

Answer 4

Blocks the Na+/K+ ATPase.

Question 5

Net glucose absorption is dependent on the presence of extracellular ….

Answer 5

sodium

Question 6

How to make brush border membrane vesicles?

Answer 6

homogenise tissue from the intestine, centrifuge to separate the two membranes.

Question 7

Describe a brush border membrane vesicle.

Answer 7

The outside of the vesicle represents the lumen and the inside represents the intracellular compartment. We can change both environments to mimic absorption across the apical membrane.

Question 8

The overshoot is typical of a …

Answer 8

carrier mediated transport process

Question 9

L-glucose movement is…

Answer 9

passive

Question 10

D-glucose movement is…

Answer 10

carrier mediated

Question 11

Phlorizin is a…

Answer 11

inhibitor of the D-glucose carrier mediated transport process.

Question 12

As well as D-glucose, what is also a substrate of SGLT1?

Answer 12

D-galactose

Question 13

What is not a substrate of SGLT1?

Answer 13

D-fructose and L-glucose.

Question 14

What experiment identifies the tissues in which SGLT1 is expressed?

Answer 14

Northern blot

Question 15

Where did the northern blot identify SGLT1?

Answer 15

Duodenum, jejunum, ileum, kidney and lungs.

Question 16

What technique identifies where in the tissue the transporter is expressed?

Answer 16

Immunostaining.

Question 17

What stain identifies the nucleus?

Answer 17

DAPI

Question 18

Can a patient with GGM syndrome absorb fructose?

Answer 18

Yes, they have a problem with SGLT1 which does not transport fructose.

Question 19

The D28N mutation of SGLT1 means the protein is…

Answer 19

missorted and not trafficked to the membrane.

Question 20

Immunostaining of the SGLT1 with the C292Y mutation shows the protein is…

Answer 20

trapped between the nucleus and the membrane

Question 21

Lactase deficiency causes…

Answer 21

Diarrhoea, intestinal cramps and flatulence.

Question 22

How is lactase deficiency treated?

Answer 22

With removal of milk products from diet or food treated with commercial lactase.

Question 23

How can lactase deficiency be identified/diagnosed?

Answer 23

Hydrogen breath test.

Question 24

Why is hydrogen tested?

Answer 24

Hydrogen is a gas produced by bacteria in the colon when they break down carbohydrates. Carbohydrates shouldn’t reach the colon in normal people as it should all be absorbed in the small intestine.

Question 25

How does the hydrogen get to the lungs?

Answer 25

50% of the hydrogen produced by the bacteria is absorbed and transported to the lungs and excreted.