Exam1Lec2TheMembranePotential

Question 1

Membrane consists of ___ and ____

Answer 1

phospholipids, proteins

Membrane has proteins that helps with adaptability to environment and communication of other cells

Question 2

Phospholipid bilayer acts as a ____ to many solutes

Answer 2

barrier

Question 3

What provides permeation pathways or act as sensors that relay signals?

Answer 3

Transmembrane proteins

Question 4

Transmembrane protein function and regulation is the essence of what three factors?

Answer 4

1. Cellular communication
2. changing cellular fxn by controlling what goes into and out of cell
3. events that occur inside cell

Question 5

Transport across the membrane can take place via

Answer 5

1. Diffusion: solutes/species can simply diffuse
2. Carrier proteins: provide help for solutes to cross p. membrane b/c too big or charged.
3. Ion channels: formed by proteins in lipid bilayer to provide adequate environment for ions

Question 6

Only ____ and ____ can cross the plasma membrane readily (down concentration gradient)

Answer 6

small, lipophillic

Question 7

____ and ____ need help to cross the membrane. and ____ provide this help.

Answer 7

Ions, large polar (uncharged) molecules, transpors and ion channels

Question 8

Which one is quicker, ion channels or transporters?

Answer 8

Ion channels

Question 9

Explain how ion channels work

Answer 9

They provide an aq space (filled with water) to ions can move

They are transmembrane proteins that allows specific ions to move across the membrane down their electrochemical gradient through an aq pore formed by the channel protein. Usually they require a stimulus such as a ligan binding or a change in membrane potential in order to activate

Question 10

Explain how transporters work

Answer 10

Have a receptor for a solute to binds. Once it biinds, the transporter changes conformation and opens other side losing affinity for solute and releases it.

Question 11

What is membrane potential?

Answer 11

Charge gradient producing voltage difference across membrane

a voltage diff exists across the plasma membrane and a second source of free energy acting on charged solutes
Em=Ein-Eout

Question 12

Typial resting membrane potential is
A.positve
B. negative
C. neutal

Answer 12

negative

Question 13

How does the charge gradient form?

Answer 13

different ions concentrations and selective permeabilities of those ions create charge gradient which creates membrane potential

Question 14

Movemnt of ucharged molecules are ____ by the membrane potential

Answer 14

NOT affected

This is bc for ex, you have a cell where inside is neg change, and you put cell in same area as a solure that is uncharged. The solute that is uncharges still moves down concentation grdient and does not care abt voltage diff bc solute is uncharged

Question 14

Movement of ions are affected by what two things??

Answer 14

Chemical and electrical gradients

Chemical gradient bc there is a difference of concentration b/w inside and outside cell
eletrical gradient bc there is more or less negatice and positve cells inside or outside the cell and they attract each other

Question 15

What does electrochemical potential mean?

Answer 15

The free energy acting on charged particles

2 forces determine movement of charged particles across the membrane

Question 16

The nerst eq is used to predict what?

Answer 16

Equilbrium potential for a SINGLE permeable ionic species. It reflects a balance (at equilibrium) b/w chemical and electrical gradients.

Question 17

What is the nerst equation

Answer 17

Eeq=58/z x (log co/ci)

Question 18

In this pic, is Ena positive or negative and why?

add pic slide 14

Answer 18

Posititve becuase a large inwards chemical grqdients pulls na into cell. A positive equilibrium constant is needed to balance this chemical gradient to prevent further movement of sodium inside of the cell.

Question 19

A cation will move into a cell when the membrane potential (Em) is more ____ than the equilibrium potential

Answer 19

negative

Thisis bc as K+ moves inside the cell, the inside cell becomes more positive and Em will start to move to more positve lvs closer to Ek

Question 20

A cation will move out a cell when the membrane potential (Em) is more ____ than the equilibrium potential

Answer 20

positive

K+ ions would like to move outside of cell to try and drg the Em closer to Ek

Question 21

Resting neuronal membrane potential is ____ mv

Answer 21

-70

Question 22

What determines the resting membrane potential?

Answer 22

Na+, K+, Cl- ions

Question 23

The ____ and ____ of Na+, K+, and Cl- ions set the membrane potential

Answer 23

permeabilities, concentrations

Question 24

Em wants to be closest to Eeq of ion with the highest ____ at a given time

Answer 24

permeability

Question 25

Why is Em (-70) closest to Ek (-84)?

Answer 25

At rest Em of cells is mainly permeable to K+ so the Em wants to be close to Ek b/c its the ion with the largest permeability (more K+ ion channels are open compared to rest of ions)

Question 26

What does the Goldman equation tell us?

Answer 26

It describes the resting membrane potential accounting relative permeabilities and concentration gradients of three primary permeable ions

Question 27

Permeability of an ion through the plasma membrane is dictated by what?

Answer 27

Ion channels ( high permeability if ion channel is open, low perm is ion channel is closed)

Question 28

What would cause a change in membrane potential?

Answer 28

Changing internal or external ionic concentations, the largest change in Em occurs when the concentration gradient of the ion of greatest permeability is changed (generally K+)

changing con. gradient and perm of ions

If con of K+ changes detrimental cardiac/neural/muscle conseq can occur,

Question 29

When external K+ concentration is increased, Em moves to less ____ meaning that the cell is ____.

Answer 29

negative, depolarized

Em shifts with changing K+ concentration

Question 30

If membrane potential can be estimated from the Goldman equationm then Em will change due to what two factors?

Answer 30

1. Changing Co or Ci of the ion with greatest perm (generally K+)
2. Changing relative perm of all ions

Question 31

Em shifts with changes in relative perm, what happens to Em if Pna increases? (Ena=+t67)

Answer 31

Em will be less negative because as Pna incr EM moves toward depolarized potentials

Em moves toward the eq potential of the ion of incr pem

Question 32

Em shifts with changes in relative perm, Pna increases, then Pna returns to resting values and Pk increases, what happends to Em? (Ek=-84)

Answer 32

Em shifts toward Ek, so it becomes more neg. The membrane potential will repolarize toward negative potentials reaching potentials more hyperpolarized than the resting potential.

Question 33

What are the 4 major classes of ion channels?

Answer 33

1. Leak (constantly active)
2. Stretch-activated
3. Ligand-gated
4. Voltage-Gated

Question 34

Explain Leak channels

Answer 34

These are active most of the time , providing a permeation path for a specific ion, especially at rest.

Question 35

Explain Stretch-activated channels

Answer 35

When the plasma membrane is stretched the proteins change conformation where an aq pore is formed.

Cell stretches, ion channels open (change conformation, cell generates action potential

Question 36

Explain ligand-gated channels

Answer 36

a molecule binds to the protein to activate a channel

A ligand like a neurotransmitter binds to a receptor and the channel opens (channel is ligand gated) and an influx of ions occur

Question 37

Explain voltage-gated ion channels

Answer 37

channel activated following a change in membrane potential

when voltage across membrane changes, ion channels sense dep and open and close

Question 38

What is action potential?

Answer 38

Transient changes in membrane potential caused by orchestrated opening and closing of ion channels

Question 39

The electrochemical potential which is the sum of the chemical and electrical potentials determines what three things?

Answer 39

1. Rate
2. direction
3. extent of movement of charged particles

Question 40

True or false, the plasma membrane is only permeable to 1 ion.

Answer 40

FALSE, most ions cross the membrane with some permeability

Question 41

What is the resting membrane potenial? Erest

Answer 41

The combined equilibrium potentials for all permeable ions which is calculated by the Goldman eq using the msot permeable ions (Na, K, Cl)