8-29 Membrane Potential/Transport

Question 0

Describe the extra/intraCellular Concentrations of [ K+ ]

2)Why is this?

Answer 0

K+ has LOW concentration outside/extracellular the cell

2)K+ is LOW OUTSIDE the cell because 2 K+ are pushed into cell during every rxn

Question 1

Describe the extra/intraCellular Concentrations of [ Na+ ]

Answer 1

Na+ has HIGH concentration OUTSIDE the cell

Na+ has low concentration inside cell

Question 2

Describe the extra/intraCellular Concentrations of [ Ca+ ]

Answer 2

Ca+ is High concentration OUTSIDE cell but is still relatively low in overall concentration

Question 3

Describe the extra/intraCellular Concentrations of [ Cl- ]

Answer 3

Cl- has HIGHER CONCENTRATION OUTSIDE the cell normally

Question 4

What are the 3 types of ACtive Transport mechanisms?

B)Active Transport = requires ______

Answer 4

1. Coupled Transporter [symport vs. Antiport]
2. ATP-Driven Pump (requires ATP Hydrolysis)
3. Light-Driven Pump

B)ACTIVE TRANSPORT=needs some type of “activator” for conformational change (ATP (1)vs. Na+/co-transporter ion (2))

Question 5

What is uniport?

Answer 5

Uniport (channels or carrier proteins) is an ACTIVE TRANSPORT mechanism that performs ATP DRIVEN movement of ions/charged

Question 6

What is the P-type pump

Answer 6

1 of the 3 ATP Pumps/ACTIVE TRANSPORT=Uses ATP to PHOSPHORYLATE ITSELF during ion transport

Question 7

What is the F-type/V-type proton pump [2]

**What’s special about the F-type/V-type proton pump

Answer 7

2 of the 3 ATP pumps/ACTIVE TRANSPORT=[F-type]uses ATP synthases to MAKE ATP from H+ gradient.

B-[V-type] hydrolyzes ATP and pumps H+

****this pump is MOSTLY MITOCHONDRIA BASED

Question 8

What is an ABC pump?

Answer 8

3 out of the 3 ATP pumps/ACTIVE TRANSPORT= Hydrolyzes ATP to PUMP MOLECULESS (and some ions) against their gradient

Question 9

WHAT are the 4 steps of the Na+/K+ ATP pumping cycle? [4]

Answer 9

1st: Na+ binds, ATP is hydrolyzed and cytoplasmic residues phosphorylated
2nd: Pump confirmational change occurs and Na+ is transferred out!

3rd: K+ then binds from outside cell area into pump and DEphosphoryltion occurs
4th: K+ binding and DEphosphoryltion causes confirmation change once again which shifts K+ INSIDE the cell

Question 10

What is the difference between PRIMARY and SECONDARY

Active Transport?

Answer 10

PRIMARY=Hydrolyzes ATP ONLY to move substance against its gradient

Secondary=uses co-transporter ions (like Na+) to move stuff against their gradient
[COUPLED TRANSPORT->Symport/Antiport are SECONDARY!]

Question 11

What is the ABC pump relation to MDR(Multi-Drug Resistance)

Answer 11

ABC pumps in cancer cells pump chemotherapeutic drugs OUT OF THE CELL=cancer cells become resistant to drugs

Question 12

What is the ABC pump relation to CFTR?

Answer 12

CFTR(Cystic Fibrosis Transmembrane Regulator) protein is an ABC pump that normally pushes Cl- out of the cell. When messed up…Cl-becomes trapped in cell, so other [+] ions stay trapped with Cl- and water osmosis into cell to be with ions–>leads to NO WATER BEING OUTSIDE CELL which eventually mucus becomes too thick in lungs

Question 13

What is the ABC pump relation to Plasmodium Falciparum?

Answer 13

Plasmodium Falciparum is an agent of malaria that actually uses one of our ABC pumps to transport chloroquine(malaria drug) OUT of out cell

Question 14

What is the ABC pump relation to Cystinuria?

Answer 14

genetic defect in an Amino Acid-ABC pump (which job is to normally remove cysteine dimers from urine & intestine)–>many Kidney and Bladder Cystine Stones!

Question 15

Simple diffusion __[does/DOESN’T] have a Vmax

Answer 15

Simple Diffusion DOESN’T HAVE A VMAX
vs.
(Transporter-mediated diffusion will have a Vmax)

Question 16

How exactly does the ORIGIN OF RESTING POTENTIAL come about in cells?

Answer 16

1) Liposome membrane spontaneously form around Na+, K+ and Cl- which have concentrations inside cell =concentrations outside cell
2) Na+/K+ pump placed in liposome membrane and (with ATP assistance) pumps 3 Na+ OUT and 2 K+–>creates membrane voltage because outside is more + than inside now AND chemical gradient because concentrations have changed
3) Leaky K+ channels are placed in membrane allowing K+ to just easily leave DOWN its gradient= even more [-] charge inside cell

Question 17

What is the Formula for calculating the Voltage of an ion?? What is this also known as?

3)What is [Vi]?

Answer 17

Vi= log[CONCENTRATION OUTSIDE cell]
_______________________________ = NERNST POTENTIAL
log[concentration inside]

3)Vi=Voltage of ion and electrochemical equilibrium potential for that ion and NERNST POTENTIAL

Question 18

The leaky K+ channels allow K+ to…

Answer 18

Leaky K+ channels
2)Allows K+ to diffuse DOWN its chemical gradient–>allow K+ to reach an equilibrium between chemical and electrical gradients

Question 19

What does “current” in regards to membrane potential mean?

2) Positive Voltage means____ [+/-] Current. How do you get a Positive Voltage?
3) A Positive Current will mean + ions ____[ENTER/leave]

Answer 19

Current=direction an ion (inside vs. outside cell) would go if you opened that ions channel –>based on its concentration and electrical gradient at the time

2) [+] Voltage = [+] Current. // [+] Voltage happens when Vi < VM
3) [+] Current = [+] ions LEAVE THE CELL when their channel is opened

Question 20

How do you calculate transmembrane electrochemical gradient for an ion?

Answer 20

VM (resting membrane voltage) - Vi (Voltage of the ion) =

Question 21

What forces are in equilibrium at the membrane voltage?

Answer 21

Both the chemical gradient (K+ ion wants to go down its concentration gradient and leave cell) and the electrical gradient (K+ ion wants to stay inside the cell because it’s too positive outside cell) OPPOSE each other = equilibrium

Question 22

How is Current calculated?

Answer 22

Current = Difference in Voltage = [V{Membrane} - V{ion}]

Question 23

Voltage of an ion is generated by____ [2]

Answer 23

Voltage of an ion is generated by the DIFFERENCES between that ions concentration outside cell and concentration inside cell
Vi = log[CONCENTRATION OUTSIDE]
____________________________
log [concentration inside]

Question 24

When you have a ….
[+]Voltage Difference(delta V)=[_] Current= Vi ___VM =[+]ions___the cell
**THIS IS THE GOLDEN RULE

Answer 24

[+]Voltge Difference(deltaV)=[+]Current= Vi<VM= [+]ions LEAVE the cell

Vi=Voltage of the ion
VM=Voltage of the Membrane

Question 25

What are the 3 Types of iON CHANNELS (_____ Diffusion)

Answer 25

ALL OF THESE ARE PASSIVE DIFFUSION CHANNELS {ion transport can be ACTIVE as well)

1. Voltage-Gated iON channels
2. Mechanically Gated iON channels
3. Ligand-gated [extracellular vs. intracellular ligand] iON channels

Question 26

What are the 3 BIG CATEGORIES of Passive transport

Answer 26

1) 3 types of ions channels[voltage vs. mechanical vs. Ligand]
2) simple diffusion
3) Transporter-mediated Passive Diffusion