membrane transport

Question 1

what hydrophobic molecules can get through the bilayer

Answer 1

O2, N2, CO2, benzene, short chain FA

Question 2

small uncharged polar molecules that get thought

Answer 2

h2o, urea, glycerol

Question 3

what can’t get through

Answer 3

large uncharged polar molecules, ions, charged polar molecules

Question 4

describe facilitated diffusion and give an example

Answer 4

protein
along conc gradient
no energy
can involve conformational change in selective carrier protein
e.g. GLUT - glucose

Question 5

examples of primary and secondary active transport

Answer 5

primary; Na/K ATPase

secondary: Na/glucose transporter

Question 6

what does the rate of diffusion depend on

Answer 6

partition coefficient:

K(ow) - equilibrium constant for partitioning of a molecule between oil (octanol) and water

Question 7

what does a high Kow value mean

Answer 7

more lipid soluble

Question 8

uniport/symport/antiport

Answer 8

uni:
symp:
anti:

Question 9

GLUT1 location and main function

Answer 9

• high in erythrocytes and blood brain barrier, low in skeletal muscle
• glucose uptake

Question 10

GLUT2

Answer 10

• liver, pancreas B cells
• highi Km and large Jmaz
• transport glucose into hepatocytes and B cells to when [gluc] high to regulate blood

Question 11

GLUT3

Answer 11

low Km

highest expression in neurones

Question 12

GLUT4

Answer 12

• muscle, adipocytes

- regulated by insulin: bring GLUT4 to plasma membrane

Question 13

GLUC5

Answer 13

-fructose transporter

Question 14

difference between primary and secondary active trnsport

Answer 14

primary: hydrolysis of ATP
secondary: electrochemical gradient

Question 15

examples of primary active trans

Answer 15

• NA/K-ATPase in plasma membrane
• H-ATPase in lysosomal membarane
• Ca-ATPase in plasma membrane and sarcoplasmic reticulum of muscle

Question 16

what type of process is secondary active trans

Answer 16

electrogenic: produce change electrical potential of cell

Question 17

why is NA/K-ATPase a drug target in heartfeailutre

Answer 17

• oubain blocks pump - prevent K binding
• increase intracellular [Na]
• inhibits Na/Ca antiporter
• increase in intracellular[Ca] = trigger cardiac muscle contrction

Question 18

what is purple foxglove a source of

Answer 18

digitoxin and digoxin – cardiotonic drugs, increase contraction

Question 19

what is secondary active trans important in

Answer 19

1. intestinal epithelial cells - absorb glucose

2. epithelial cells in PCT - reabsorb glucose

Question 20

e.g. of secondary A transprter

Answer 20

Na/Gluc transporter

SGLUT1

Question 21

what does cholera do

Answer 21

• Vibrio cholerae = causes electrolyte and fluid secretion

- toxin = Cl excreted by over activating Gsa = activate adenylyl cyclase and increase cAMP

Question 22

Role of the Na+/Glucose Cotransporter in Electrolyte Replacement Therapy in Cholera

Answer 22

a high concentration of glucose (~110 mM) which drives Na+ (and consequently Cl- and H2O) back into the intestine through the Na+/glucose cotransporter

Question 23

how is the transport of glucose aided

Answer 23

Binding of D-glucose to an extracellular domain causes the conformational change, polar amino acids within the bilayer core Hydrogen bond to the hydroxyl groups of glucose thereby facilitating its movement