lecture 3

Question 1

need for energy in active transport

Answer 1

• cells maintain conc. gradient
• energy from ATP
• performed by specific proteins embedded in membranes

Question 2

ion pumps maintain membrane potential

Answer 2

• membrane potential = voltage difference across membrane
• created by difference in distributions of positive and negative ions
• collectively create electrochemical gradient (drive diffusion)
• chemical force = ions conc. gradient
• electrical force = effect of membrane on ions movement

Question 3

electrogenic pump

Answer 3

• transport protein that generates voltage across membrane
• animals: sodium-potassium pump
• plants: proton pump

Question 4

coupled transport

Answer 4

• active transport a solut indirectly
• plants: H+ gradient (proton pump)

Question 5

bulk transport

Answer 5

• large molecule can not pass throug lipid bilayer
• cross membrane in bulk (vesicles)