Movement Across Membranes

Question 1

why is membrane fluidity crucial to cell function

Answer 1

• cell fluidity must be maintained

- lipid composition of membraned can be changed

Question 2

how can lipid composition of membranes be changed

Answer 2

• desaturation of fatty acid chains

- exchange of fatty acid chains

Question 3

describe movement of small, uncharged molecules across cell membrane

Answer 3

small uncharged molecules move across membrane relatively easily (O2, CO2, NO, H2O)

Question 4

describe movement of large/polar/charged compounds across cell membrane

Answer 4

they can not easily cross lipid bilayers

Question 5

what are the four mechanisms for moving molecules across membranes

Answer 5

1) simple diffusion
2) diffusion through a channel
3) facilitated diffusion
4) active transport

Question 6

what are the two non-mediated ways of moving molecules across membranes

Answer 6

1) simple diffusion

2) diffusion through a channel

Question 7

what are the two mediated ways of moving molecules across membranes

Answer 7

1) facilitated diffusion

2) active transport

Question 8

describe simple diffusion

Answer 8

for very small molecules (uncharged), follows down a concentration gradient

Question 9

describe diffusion through a channel

Answer 9

for small, uncharged molecules

down a concentration gradient

Question 10

how are ion channels formed

Answer 10

they are formed by integral membrane proteins that line tan aqueous pore

Question 11

describe ion channels

Answer 11

• selective
• down concentration gradient
• often gated
• important in nerve cell function

Question 12

what are water channels called

Answer 12

aquapores

Question 13

what is a dimer

Answer 13

two proteins stuck together (non-covalent)

Question 14

what are the two types of gated channels

Answer 14

1) voltage gated

2) ligand-gated

Question 15

describe voltage gated channels

Answer 15

they respond to changed in charge across membraned

Na,K

Question 16

describe ligand-gated channels

Answer 16

they respond to binding of specific molecules (a ligand duh) (like acetylcholine)

Question 17

describe facilitated diffusion

Answer 17

• compounds bind specifically to integral membrane protein called a facilitative transporter
• a change in transporter confirmation allows compound two be released on the other side of membrane
• compound moves down a concentration gradient

Question 18

what is needed to move substances for lower conc to higher conc

Answer 18

energy is required :)

energy is provided by the chemical gradient provided by high [Na] outside the cell

Question 19

describe active transport

Answer 19

• compounds bind specifically to integral membrane proteins called an active transporter
• change in transporter confirmation allows command to be released on other side of membrane
• compound moves again concentration gradient
• requires energy
• the NA/K ATPase maintains cellular [Na} and [K] using ATP

Question 20

what does the Na/K ATPase maintain

Answer 20

cellular [Na] and [K] using ATP

Question 21

ligand:

Answer 21

opens gate (door man)

Question 22

Fugu poisonous fish

Answer 22

tetrotoxin

it is an Na+ channel blocker

Question 23

example of facilitated transport

Answer 23

glucose transporter