Lecture 17 - Transport Across Membranes (Ch 12) Flashcards
(37 cards)
The region of an ION channel that becomes narrow is called a __ __
selectivity filter
What does ms. ion channel select her clients based on?
She chooses her clients based on how wide they are (ugh ik! but diameter), what shape they are (so discriminatory), and their charge (talk about highly selective!) $$$ but in AA side chains
What does a stimulus do for ion channels>?
Stimulation opens the gates of the Gated Ion Channel
What is faster in opening and closing/passing things, a channel or transporter? And by how much
A channel is 1000x faster
Ions flow through an ion channel fast and lots at a time because of the electrochem gradient made in advance by:
pumps!
What cation is highest outside the cell?
salt
What cation is highest inside the cell?
potassium
What helps balance some of the Na+ outside the cell?
Chloride anions
What helps balance some of the K+ inside the cell?
Negative charges on inorg AND org ions
What is our resting membrane potential and what does this mean for the charge inside the cell?
-20 milivolts to -200 millivolts; it means the inside of cell is more negative
What channels are OPEN in RESTing cell; what is the purpose of this?
K+ Leak channel ONLY; it moves k out of cell until electrochem gradient (for K only) = 0 ->mem potential is now -20 to -200 mv range
10x change in ion concentration changes membrane potential by how much
62 mv
A pipette with wire help you tear off a single channel from a membrane to study it. you adding a wire can help make a circute. what is this technique called?
Patch clamp technique
True or false, ion channels randomly open and close
True, and very fast too (they fully open and fully close, not in between)
What are the different stimuli types that can affect membrane potential?
Ligand binding, mechanical stress, and membrane potential (aka voltage gating)
Give two examples of mechanical (aka stress gated ) channels
Our ear stereocilium respond to the physical sound waves we hear! Also, the mimosa plant will close if you touch it (but this plant one is mech gated AND volt gated(depolarization))
Whats the key to maintaining resting potential in cells?
K+ channels
What part of the nerve cell recives signals?
THe dendrite, which is attached to the cell’s body (like a lil omlet with egg fratgments)
How are signals delivered so that membrane potentials are spread efficiently?
The signal first gets delivered to the dentrite (localarea ->localized change) and cell body area, and travels through the axon (like the stalk of a dandelion!), and to the terminal
How do volt gate ion channels respond to and affect membrane potential? name the 3 steps and what is ultimately created.
First, the voltgateion channel opens bc membrane potential has shifted a lil bit. Next, ions go through the channel to shift it even more. Lastly, the newly shifted mem potential trickles down activating more channels to open ‘em (making a circuit)
Nerve impluses, aka ____, help membrane potential shifts to TRAVEL across the body to reach a certain area
nerve impulses
describe how action potentials spread!
Na+ voltage gated channel opes and changes potential, opening more, and then after 1 msec they close
For an action potential to actually happen, what has to happen to cross the threshold potential level?
You have to have enough power in you r initial depolarization stimulus that you reach the minimum (threshold) to spread (amplify) your signal!
True or false, K+ leak channels repolarize the membrane.
false- they are not fast enough.
