Membrane Properties Flashcards
Membrane proteins can be categorized according to:
- Structure
2. Function
What are the “structure” proteins
- Integral; span both layers
2. Peripheral proteins; found only on one side
What are the “function” proteins
- structural proteins
- membrane transporters
- membrane enzymes
- membrane receptors
which proteins do the membrane transporters consist of
- Carrier proteins: change conformation
2. Channel proteins: form open and gated channels
Where are structural proteins found in
- cell junctions
2. cytoskeleton
What are membrane enzymes active in
- metabolism
2. signal transfer
what are membrane receptors active in
receptor mediated endocytosis, signal transfer and and open and close chemically gated channel
Na/K pump more of an enzyme bc uses energy of ATP, hydrolyzes it and changes conformation of :
carrier
Electrical potentials are generated across the membranes of neurons and all cells bc:
- There are diff’s in the conc’s of specific ions across nerve cell membranes
- the membranes are selectiviely permeable to some of these ions.
What is the ion conc. gradients are est by which proteins
active transporters; actively move ions into/out of cell against their conc gradient.
The selective permeability of membranes is due to:
ion channels; allow only certain kinds of ions to cross the membrane in the direction of their conc gradient.
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
against; resting membrane potential
The cell body and the dendrites is called the _____ domain
somatodendritic
The axon and nerve termini is called the ____domain
axonal
what is a ligand gated ion channel
they need something to bind to it (ligand aka neurotransmitter) in order to open/close
Ligand gated channels are mainly located where
somatodendritic domain
what are voltage gated Na/K+ channels
Requires a change in electrochemical potential in order to open/close it.
Where are voltage gated channels mainly
in the axonal domain
How come action potentials don’t go the opposite way? ( Nerve termini –>cell body)
specific spatial distribution of Na/K+ voltage gated channels
You will always see a greater amount of ____ions intracellular and lower amount of ___ and ___ ion
K+; Cl- and Na+
All fluids and cells maintain __ ____ which means that the # of pos charges = # of negative charges
bulk electroneutrality
What are the ionic gradients used for
- Used by secondary active transport processes
2. Used by excitable cells, allowing production of action potentials
Fixed proteins which have a lot of negative charges are found in which part of the cell
inside
There is a slight ____charge inside the cell relative to outisde of the cell
inside
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
ionic; membrane
In most cases, the resting membrane potential is due to leaking of ____ion out of the cell without a counter ion balancing the charge
K+
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:
- how much ions you have on other side
2. how much your membrane is permeable
The driving force for passive transport across the membrane is influenced by a _____gradient for nonelectrolytes
concentration
The driving force for passive transport across the membrane is influenced by concentration gradient and _____gradient for ions
electrical
Ions come into electrochemical equilibrium where net flux of the ion may = 0, even if there is still a ____gradient
concentration
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 ____
greater; greater
If the conc of ions are the same on both sides what would happen?
nothing
If there is a higher conc on one side and it is permeable it will go on which side?
the side that has less
What are pseudo cellular conditions
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.
What does the Nernst eqn show us
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
Is the eq potential for Na+ positive or neg? What about K+ and Cl-
positive; negative; negative
Na goes ___ K goes ___ and Cl goes ____
in; out; out
Which ion is most permeable?
K+ is the main ion that we allow to permeate through selectively permeable membrane
If the gradient for a given ion /permeability for an ioc across the membrane changes what else changes?
the membrane potential! AKA Vm
What is the difference between Goldman Hodgkin Katz equation and Nernst equation.
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.
What is equilibrium potential
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.
what is membrane potential
a REAL value that can be measured.
What is the voltage of a membrane a function of
the resistance of the membrane to ion flow and the actual flow (current)
Resistance is:
futile
What is conductance
ion flow rate; the inverse of resistance
What is the purpose of a patch clamp
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.
what is current in a normal living cell
ions that create electrical impulses
What are the diff ways of patch clamping.
- putting on channel and recording it.
- rupture the cell by suction which opens the whole cell to easily record currents through the whole cell.
- You can split it off and have one specific channel
- 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
What does openings of multiple channels create
causes stepwise increases in current.
what is the magnitude of the TEPD proportional to
the tightness of the tight junctions
How do you calculate TEPD
Vb - Va
