Membrane Transport

Question 1

What type of process is Non-mediated diffusion?

Answer 1

Linear and non saturable

Question 2

Differential Permeability

Answer 2

Ability of a membrane to let some molecules through but not others

Question 3

Chemical potential

Answer 3

relative concentrations of solutes on each side of the membrane

Question 4

Electrical potential

Answer 4

relative concentrations of ions on each side of the membrane

Question 5

Uniport

Answer 5

Movement of a single molecule at a time

Question 6

Symport

Answer 6

simultaneous transport of two molecules in the same direction

Question 7

Antiport

Answer 7

simultaneous transport of two molecules in opposite directions

Question 8

Electroneutral transport

Answer 8

transport of molecules does not change charge separation across the membrane

Question 9

Electrogenic transport

Answer 9

transport of molecules that results in charge separation across the membrane

Question 10

What are the properties of facilitated transport?

Answer 10

requires carrier proteins, exhibits substance specificity, can be inhibited like an enzyme, kinetics are non-linear and saturable

Question 11

What are the two classes of Transport Proteins?

Answer 11

Carrier protein and channel protein

Question 12

Channel proteins

Answer 12

Passive mediated diffusion, consist of water-filled pores which cross the membrane

Question 13

Ionophores

Answer 13

disrupt vital concentration gradients through mediated transport of ions or compounds

Question 14

What are the two types of ionophores?

Answer 14

Carriers and Channel Formers

Question 15

Carrier proteins

Answer 15

undergo conformational changes as they transfer substance across the membrane, transport may be active or passive

Question 16

PMF

Answer 16

proton motive force

Question 17

Cotransport

Answer 17

two different substances move across the membrane in a coupled manner

Question 18

“P” class pumps

Answer 18

have several components, proteins change shape in response to auto-phosphorylation of the pump, transport ions such as H+,Na+,K+ and Ca2+

Question 19

Na+/K+ pump

Answer 19

3 Na+ for 2 K+

Question 20

“F” class pumps

Answer 20

multiple transmembrane and cytosolic subunits, synthesize ATP by moving H+ across an electrochemical gradient

Question 21

Where are F-class proton pumps found?

Answer 21

Bacterial Plasma Membrane, Inner mitochondrial membrane, thylakoid membrane of chloroplast

Question 22

“V” class pumps

Answer 22

multiple transmembrane and cytosolic subunits, Move H+ across a membrane in order to acidify a cell compartment (lysosomes)

Question 23

Where are V-class proton pumps found?

Answer 23

Vacuolar membranes in plants, yeast, other fungi, endosomal an lysosmal membranes in animal cells, plasma membrane of osteoclasts and some kidney tubule cells

Question 24

“ABC” superfamily of Pumps

Answer 24

two transmembrane domains form a pathway, Use ATP binding and hydrolysis to move the solute, transport small molecules (sugars, phospholipids, peptides)

Question 25

Where are “ABC” pumps found?

Answer 25

Mammalian plasma membranes, bacterial plasma membranes

Question 26

What are the 3 types of coupled transport?

Answer 26

1. Use concentration gradient to couple uphill transport of 1 molecule with downhill transport of another
2. ATP-driven pumps couple uphill transport to hydrolysis of ATP
3. Light- or redox-driven pumps in bacteria couple uphill tranpsort to energy from light

Question 27

Competitive inhibitors

Answer 27

compete for the same binding site

Question 28

Noncompetitive inhibitors

Answer 28

bind elsewhere and alter the structure of the transporter

Question 29

What is G-protein Switching?

Answer 29

When a “G” protein is bound to GTP the switch is “on” (or “off”)
The G protein has intrinsic GTPase activity.
Use a GTPase Activating Protein (GAP) to activate the GTPase activity of the protein
This forms a “G” protein that is bound to GDP and triggers a conformational change in the shape of the protein that switches the protein to an “off” stat (or “on”)
Use a GTP Exchange Protein (GEF) to cause exchange of the GDP for a GTP to reactivate the protein. A conformational change in the shape of the protein will switch the protein to the “on” (or “off”) position or structure