Lecture 9: Membrane Transport, Part II

Question 1

Ion channels

Answer 1

• Form pores across lipid bilayer and allow passage of charged molecules through cell membrane
• Do not change shapes to transport individual solutes across membrane
• Only passive transport

Question 2

Ion channels can be open or closed which allow

Answer 2

effienency as when open channels, polar molecules can flow 1000 times faster than transporters

Question 3

Ion channels have specificity with

Answer 3

selective filter that are protein structures of narrow region of ion channel on one end that determines what ions can pass through pore

regulates size and charge of each ion to pass through

Question 4

Other end of ion channel forms gates that can be opened or closed which helps

Answer 4

not changing shape for every individual solute traveling through

Question 5

Big advantage is efffiency to ion channels, but trade off is

Answer 5

only passive transport

Question 6

Opening of ion channel is regulated by

Answer 6

different gating mechanisms

Question 7

Voltage gated

Answer 7

Opening controlled by voltage inside cell
protein structures can detect charge on inside cell and shape change depending on negative and positive charge

positive charge opens channels

Question 8

Ligand gated

Answer 8

opening controlled by binding of a molecule (ligand) to the channel
channels have binding sites not for solute traveling, but for signaling molecules
Signaling molecule bind to binding site on ion channel to cause conformational change of ion channel t open

Question 9

Mechanically gated

Answer 9

opening controlled by mechanical stress

Question 10

Concentration of ions is tightly regulated in cells by ___ and ___ to provide _____

Answer 10

transporters and channels
equilibrium

Question 11

Concentration outside cell and inside cell

Answer 11

outside: high concentration of sodium (Na+) and chloride ions to neutralize positive charge

inside: high concentration of potassium (K+) and DNA to neutralize positive charge

Question 12

Membrane potential

Answer 12

voltage difference (charge) between inside and outside of cell

Question 13

Resting membrane potential

Answer 13

ensures Na+-K+ pump is working to maintain negative charge inside cell

animal cell is -20 to -200 mV

Question 14

K+ leak channels

Answer 14

Doing minor adjustments to maintain resting membrane potential in animal cells
Usually open and allow passive transport of K+ to travel outside cell down concentration gradient
K+ push out to make cell more negative

Question 15

When electrochemical gradient for K+ is zero and has no movement, cell is at

Answer 15

resting membrane potential

Question 16

Slight negative charge inside cell is governed by:

Answer 16

1. Na+-K+ pump
2. K+ leak channels:
   if too + on inside, start to push K+ out
   if too - on inside, start to pull K+ in

Question 17

Na+K+ pump is ___ while K+ leak channels go

Answer 17

consistent
back and forth

Question 18

Neurons function to

Answer 18

receive and transport signals

Question 19

Cell body of Neuron

Answer 19

contain nucleus and most organelles

Question 20

Dendrites of Neuron

Answer 20

short extensions from cell body that receive signals from other cells

Question 21

Axon of Neutron

Answer 21

long extension that branches at end to send electrical signals away from cell body and to target cells

Question 22

Signaling initiates in

Answer 22

cell body (acts as headquarters) to make decision whether to fire or not to change membrane potential

Question 23

Nerve terminal of Neutron

Answer 23

end of axon that send signals (neurotransmitters) to target cell

Question 24

Cell body receives signals to change _____ and shoot down _____

Answer 24

membrane potential
axon terminal