Membrane transport

Question 1

Structure of GLUT Transporter

Answer 1

12 transmembrane alpha helices

Question 2

Type of transport GLUT carries out

Answer 2

Facilitated diffusion

Question 3

High affinity GLUT transporter

Answer 3

GLUT 1,3,4

Question 4

Low affinity GLUT transporter

Answer 4

GLUT 2,5

Question 5

Where is GLUT-1 found?

Answer 5

RBC, blood-brain barrier, kidney

Question 6

Where is GLUT-3 found?

Answer 6

neurons, brain

Question 7

Hereditary GLUT-1 deficiency

Answer 7

metabolic encephalopathy

• At birth, microcephaly and seizures
• individuals mature and have ataxia, delayed psychomotor development, movement disorders, impaired speech

Question 8

Where is GLUT-2 found?

Answer 8

intestinal mucosal cells
hepatocytes
pancreatic beta cells
renal tubular cells

Question 9

Job of GLUT-2 in intestinal mucosal cells

Answer 9

release dietary monosaccharides into portal vein

Question 10

Job of GLUT-2 in hepatocytes

Answer 10

facilitate glucose uptake from blood into hepatocytes at high blood glucose levels after a meal, also release glucose into blood during fasting

Question 11

Job of GLUT-2 in pancreatic beta cells

Answer 11

measure high blood glucose levels, leading to high ATP and release of insulin

Question 12

Job of GLUT-2 in renal tubular cells

Answer 12

re-uptake of glucose

Question 13

Where is GLUT-4 found?

Answer 13

fat cell, skeletal muscle and heart

Question 14

Relationship between insulin and GLUT-4

Answer 14

Insulin mobilize transport of GLUT-4 from intracellular pool to plasma membrane. Once GLUT-4 is aligned in plasma membrane, it allows the influx of blood glucose into cell.

Question 15

How does insulin injection might lead to hypoglycemia?

Answer 15

Due to Rapid uptake of blood glucose into skeletal muscle and fat cell via mobilized GLUT-4

Question 16

What can stimulate mobilization of GLUT-4?

Answer 16

Insulin and vigorous exercise

Question 17

Where is GLUT-5 found?

Answer 17

intestinal mucosal cell on luminal side of intestinal membrane
seminal vesicle

Question 18

Role of GLUT-5

Answer 18

transports mainly dietary fructose and dietary glucose only at very high level of glucose concentration

Question 19

Role of GLUT-5 especially in seminal vesicle

Answer 19

for release of fructose into semen.

use blood glucose to form fructose to supply the energy metabolism of sperm cells.

Question 20

What type of transport is SGLT?

Answer 20

Secondary active transport

Question 21

Role of SGLT-1

Answer 21

Symporter that transport sodium ions and glucose or sodium ions and galactose into intestinal mucosal cells

Question 22

Role of SGLT-2

Answer 22

Found in kidney and transports sodium ions and glucose for re-uptake

Question 23

In eukaryotes, what molecules use ABC transporters?

Answer 23

lipids or lipid-related compound.

Question 24

Example of ABC Transporter

Answer 24

Liver release bile salts, cholesterol and conjugated bilirubin into the bile ducts using ABC transport

Question 25

What type of transport is CFTR?

Answer 25

special ABC-transporter, but considered as facilitated diffusion because chloride ions flow with the gradient from inside to outside of cell.

Question 26

Symptoms of Cystic fibrosis

Answer 26

``` salty skin for newborn poor growth and low weight recurrent lung infecion chronic pancreatitis Steatorrhea Male infertility ```

Question 27

How is the release of water to extracellular surfaces dependent on CFTR function?

Answer 27

In a typical epithelial cell, chloride ions are first accumulated inside the cell. Then, chloride ions are released into extracellular lumen through CFTR. Then sodium ions from interstitial fluid binds with Cl in the lumen to form sodium chloride with attracts water.

Question 28

Where is CFTR present?

Answer 28

``` epithelial cells of airway ducts pancreatic ducts reproductive ducts skin ```

Question 29

What is different between CFTR in skin and other places?

Answer 29

CFTR in epithelial cells of sweat secretory duct when opened, chloride ion flow with the gradient into epithelial cells from the duct lumen, being used as re-uptake of chloride ions by epithelial cells. (sweat formed in coil has higher conc of NaCl than those in epithelial cell)