Membrane Properties

Question 1

Membrane proteins can be categorized according to:

Answer 1

1. Structure

2. Function

Question 2

What are the “structure” proteins

Answer 2

1. Integral; span both layers

2. Peripheral proteins; found only on one side

Question 3

What are the “function” proteins

Answer 3

1. structural proteins
2. membrane transporters
3. membrane enzymes
4. membrane receptors

Question 4

which proteins do the membrane transporters consist of

Answer 4

1. Carrier proteins: change conformation

2. Channel proteins: form open and gated channels

Question 5

Where are structural proteins found in

Answer 5

1. cell junctions

2. cytoskeleton

Question 6

What are membrane enzymes active in

Answer 6

1. metabolism

2. signal transfer

Question 7

what are membrane receptors active in

Answer 7

receptor mediated endocytosis, signal transfer and and open and close chemically gated channel

Question 8

Na/K pump more of an enzyme bc uses energy of ATP, hydrolyzes it and changes conformation of :

Answer 8

carrier

Question 9

Electrical potentials are generated across the membranes of neurons and all cells bc:

Answer 9

1. There are diff’s in the conc’s of specific ions across nerve cell membranes
2. the membranes are selectiviely permeable to some of these ions.

Question 10

What is the ion conc. gradients are est by which proteins

Answer 10

active transporters; actively move ions into/out of cell against their conc gradient.

Question 11

The selective permeability of membranes is due to:

Answer 11

ion channels; allow only certain kinds of ions to cross the membrane in the direction of their conc gradient.

Question 12

Channels and transporters work ____each other, and in doing so they genereate the ___ ___ ___, action potentials, the synaptic potentials, and receptor potentials that trigger the action potentials

Answer 12

against; resting membrane potential

Question 13

The cell body and the dendrites is called the _____ domain

Answer 13

somatodendritic

Question 14

The axon and nerve termini is called the ____domain

Answer 14

axonal

Question 15

what is a ligand gated ion channel

Answer 15

they need something to bind to it (ligand aka neurotransmitter) in order to open/close

Question 16

Ligand gated channels are mainly located where

Answer 16

somatodendritic domain

Question 17

what are voltage gated Na/K+ channels

Answer 17

Requires a change in electrochemical potential in order to open/close it.

Question 18

Where are voltage gated channels mainly

Answer 18

in the axonal domain

Question 19

How come action potentials don’t go the opposite way? ( Nerve termini –>cell body)

Answer 19

specific spatial distribution of Na/K+ voltage gated channels

Question 20

You will always see a greater amount of ____ions intracellular and lower amount of ___ and ___ ion

Answer 20

K+; Cl- and Na+

Question 21

All fluids and cells maintain __ ____ which means that the # of pos charges = # of negative charges

Answer 21

bulk electroneutrality

Question 22

What are the ionic gradients used for

Answer 22

1. Used by secondary active transport processes

2. Used by excitable cells, allowing production of action potentials

Question 23

Fixed proteins which have a lot of negative charges are found in which part of the cell

Answer 23

inside

Question 24

There is a slight ____charge inside the cell relative to outisde of the cell

Answer 24

inside

Question 25

While all cells maintain a membrane potential, the actual voltage varies by cell type and is influenced by _____concentration gradients and _____permeability to those ions

Answer 25

ionic; membrane

Question 26

In most cases, the resting membrane potential is due to leaking of ____ion out of the cell without a counter ion balancing the charge

Answer 26

K+

Question 27

cells are not + or - charged. Areas close to plasma membrane has a slight electrical potential diff between outside and inside. The charges are affected by two diff forces:

Answer 27

1. how much ions you have on other side

2. how much your membrane is permeable

Question 28

The driving force for passive transport across the membrane is influenced by a _____gradient for nonelectrolytes

Answer 28

concentration

Question 29

The driving force for passive transport across the membrane is influenced by concentration gradient and _____gradient for ions

Answer 29

electrical

Question 30

Ions come into electrochemical equilibrium where net flux of the ion may = 0, even if there is still a ____gradient

Answer 30

concentration

Question 31

If the membrane potential is negative inside, there will be a _____ driving force than expected from the conc. gradient alone b/c the inside negatic charge attracts the + charged cation. The rate of the flux will be ____

Answer 31

greater; greater

Question 32

If the conc of ions are the same on both sides what would happen?

Answer 32

nothing

Question 33

If there is a higher conc on one side and it is permeable it will go on which side?

Answer 33

the side that has less

Question 34

What are pseudo cellular conditions

Answer 34

When you have different molecules on both sides of membranes, but only one (usually K+) is permeable. You don’t get as much movement as you would if there were same molecules on each side.

Question 35

What does the Nernst eqn show us

Answer 35

allows us to predict the membrane potential at which a given ion will be at eq. It can determine the relative driving force for ion flux and which way an ion will move across the membrane

Question 36

Is the eq potential for Na+ positive or neg? What about K+ and Cl-

Answer 36

positive; negative; negative

Question 37

Na goes ___ K goes ___ and Cl goes ____

Answer 37

in; out; out

Question 38

Which ion is most permeable?

Answer 38

K+ is the main ion that we allow to permeate through selectively permeable membrane

Question 39

If the gradient for a given ion /permeability for an ioc across the membrane changes what else changes?

Answer 39

the membrane potential! AKA Vm

Question 40

What is the difference between Goldman Hodgkin Katz equation and Nernst equation.

Answer 40

You can put diff conc ( in and out) for diff ions you have to get direct value for membrane potential which is very close to what you see in vivo (living cell) than Nernest equation. Nernst equation gives you theoretical equilibrium potential for only one ion.

Question 41

What is equilibrium potential

Answer 41

A theoretical value of what the Vm will be when/if the ion is at equilibrium. eq potential is what cells are aiming for when they’re generating membrane potential but it doesnt reach that high bc there are a lot of ions involved as well.

Question 42

what is membrane potential

Answer 42

a REAL value that can be measured.

Question 43

What is the voltage of a membrane a function of

Answer 43

the resistance of the membrane to ion flow and the actual flow (current)

Question 44

Resistance is:

Answer 44

futile

Question 45

What is conductance

Answer 45

ion flow rate; the inverse of resistance

Question 46

What is the purpose of a patch clamp

Answer 46

measures ion flow through a single channel; place tip of glass pipette on cell membrane and pick up selective channels. If it opens/closes you can record the current and voltage.

Question 47

what is current in a normal living cell

Answer 47

ions that create electrical impulses

Question 48

What are the diff ways of patch clamping.

Answer 48

1. putting on channel and recording it.
2. rupture the cell by suction which opens the whole cell to easily record currents through the whole cell.
3. You can split it off and have one specific channel
4. You can invert it; remove glass pipette which removes phospholipids and drags a channel with it. When it anneals, you have a channel and the inside of electrode is like inside of cell

Question 49

What does openings of multiple channels create

Answer 49

causes stepwise increases in current.

Question 50

what is the magnitude of the TEPD proportional to

Answer 50

the tightness of the tight junctions

Question 51

How do you calculate TEPD

Answer 51

Vb - Va