lecture 19

Question 1

diffusion

Answer 1

molecules move from one location to another by random, thermally driven motion

Question 2

2 things that rate of diffusion depends on

Answer 2

1. size (smaller= faster)
2. solubility (hydrophobic= faster)

Question 3

What is the membrane potential?

Answer 3

the voltage difference across the membrane (about 200mV)

Question 4

transporters

Answer 4

only transport molecules/ions that fit into specific binding sites

Question 5

channels

Answer 5

allow solutes through a channel, discriminate based on size and charge

Question 6

3 characteristics of passive transport

Answer 6

diffusion of a small polar molecule

spontaneous movement of a solute down its electrochemical gradient

channels and transporters can do passive transport

Question 7

moving a solute against its electrochemical gradient

Answer 7

active transport

Question 8

active transport is performed by

Answer 8

pumps

requires energy

Question 9

osmosis

Answer 9

movement of water down its concentration gradient from low to high solute concentration

Question 10

aquaporins

Answer 10

channel proteins.
allow flow of water across plasma membrane.
mechanism: contractile vacuoles and rigid cell walls

Question 11

glucose transporter is a

Answer 11

multipass transmembrane protein

does passive transport by changing its conformation

the flow of glucose ca go either way– depending on the concentration gradient

Question 12

3 ways that pumps perform active transport

Answer 12

1. coupled pumps
2. ATP driven pumps
3. light driven pumps

Question 13

coupled pump

Answer 13

links uphill transport of one solute w the downhill transport of another

Question 14

ATP driven pumps

Answer 14

hydrolyze ATP to drive uphill transport

Question 15

light driven pumps

Answer 15

use energy derived from sunlight to drive uphill transport

Question 16

Na+ pump– what goes in and out of cell?

Answer 16

pumps Na+ out of the cell and 2 K+ into the cell at the expense of ATP

Question 17

Na+ pump concentration gradient

Answer 17

maintains a steep concentration gradient

high Na+ outside cell, high K+ inside cell

high Na+ outside acts like a dam storing energy

Question 18

Ca2+ pump

Answer 18

pumps Ca2+ out of the cell at the expense of ATP

Question 19

3 types of coupled pumps

Answer 19

uniport= only carries one solute

symport= moves two solutes in same direction

antiport= moves two solutes in opp directions

Question 20

Glucose-Na+ symport

Answer 20

found on the apical side of gut cells

uses import of Na+ to drive the import of glucose

both Na+ and glucose must be present

Question 21

plants, bacteria and fungi use — gradients

Answer 21

H+

–> increased [H+] in lysozome, gradient generated by H+ pumps will pump H+ out of the cell