Chapter 12 Flashcards
which molecules can pass thru the lipid bilayer via simple diffusion (order)
can pass thru (hydrophobic)
-non polar molecules (O2,CO2,steroid, hormones)
only partially (hydrophilic)
-small uncharged polar molecules (water,ethanol)
then
-large uncharged polar molecules (amino acids,glucose)
cannot pass thru (hydrophilic ions)
-charged molecules
which would diffuse across a cell membrane most easily
small, uncharged, non polar molecules
water can form a ____charge around ions
hydration charge
where are the higher levels of Ca+ in the cell
higher outside cell (ECF)
where are the higher levels of H+ in the cell
higher inside cell (ICF)
where are the higher levels of K+ in the cell
higher inside the cell (ICF)
where are the higher levels of Na+ in the cell
higher outside the cell (ECF)
using the sodium potassium pump which way do Na and K move
3 Na+ out
2 K+ in
what are the charges inside vs outside the cell and which way do molecules want to move
(-) inside
(+) outside
- want to move from (+) to (-)
what is passive transport and the two types
- no ATP required
- moves along concentration gradient
2 types:
simple diffusion & facilitated diffusion
what is simple diffusion
- no proteins
- no ATP
- conc gradient
what are the two types of facilitated diffusion
transporters & channel proteins
describe transporter facilitated diffusion
- binds solute one side of the membrane and changes conformation to transport solute to other side of membrane (specific shape to accept)
- slower rate than channel
- specifically glucose transporters
- can move in either direction
describe channel facilitated diffusion
- usually transport of ions
- gated / ungated
what are the types of gated channel facilitated diffusion
- voltage gated (energy/ voltage)
- mechanically gated (pressure/touch)
- ligand gated (neurotransmitters)
what is active transport and the 3 types
ATP is required
-secondary
-primary
-light driven
describe light driven active transport
bacteriorhodopsin-proton pump
describe primary active transport with an example
ex. Na+/K+ pump
- 3 Na out and 2 K into cell
- both are moving AGAINST concentration gradient
- energy is needed for this by direct ATP hydrolysis
in many cells Na/K pump generates the ________
resting membrane potential
describe secondary active transport
- coupled transport of two solutes! (symport & antiport)
- has a driving ion used to drive uphill transport of a second solute
- uses an already established gradient
what is symport vs antiport
symport - both going same ways
antiport - going opposite ways
how specifically in secondary active transport is there transport of two solutes
-ATP powered pump transports one solute to build up the electrochemical gradient
- this gradient drives transport of second solute via a !different! channel or transporter
3 types of transporters involved in transport of glucose
- Na/K pump
- Na driven glucose symport
- passive glucose transporter
ion channels have ___ diversity
lots of
pores are ____ selective and often ____
highly selective and often gated
what can trigger the opening/closing of a channel and channels are highly ____
- ligand binding
- mechanical stimuli
- voltage change
highly selective
what are voltage gated channels important for and why
excitable cells
- because they open/ close in response to the membrane potential and reaching a particular threshold triggers channels to open
what is the voltage of the threshold and resting membrane potential
RMP = -70mv
Threshold = -55mv
describe the resting membrane potential (RMP)
= -70
- voltage gates closed
- potassium ion (K) ESTABLISHES resting membrane potential
- Na/K pump MAINTAINS -70
what must first be produced before an action potential can be
graded potentials
- depolarize the cell to threshold and if threshold is reached causes an action potential
- are ligand gated
will a stronger stimulus cause a larger action potential ? why
NO because it’s an all or nothing response
once the stimulus reaches the threshold (-55mv) what happens
-opening of voltage gates
depolarizing
1. sodium comes into the cell FIRST and reaches 30 mv where the Na voltage gates close and inactivate
repolarizing
2. potassium (K) goes out of the cell and K voltage gates open
hyperpolarizing
- K gates still open / Na gates close
- Na/K pump moves hyperpolarization back to RMP
describe absolute refractory period vs relative refractory period
absolute RP (de & repolarizing phases)
- voltage gated sodium (Na) channels OPEN
- neuron cannot generate another AP
relative RP (hyperpolarizing phase)
- voltage gated sodium (Na) channels CLOSED
- second AP can only occur with a larger than normal stimulus
how do action potentials propagate
by depolarizing the section of membrane directly adjacent to it and as this spread along each section then undergoes repolarization after
what part of neuron receives the stimulus ?
dendrites
how is an impulse transmitted from one neuron to another (4)
- AP travels along presynaptic neuron and arrives at axon end terminal
•voltage gated calcium channels open
•calcium rushes in
•neurotransmitter vesicles mobilize - neurotransmitter vesicles fuse with membrane
- at membrane release neurotransmitters that diffuse across the synaptic cleft
- neurotransmitters bind to ligand gated sodium (Na) channels on post synaptic cleft causing them to open and Na rushes in
(causes a graded potential that could reach threshold and cause an AP / repeat whole process over again)
what is the synaptic cleft
gap between pre and post synaptic cells
what is the synapse
site of communication between two neurons
what and EPSPs and IPSPs
EPSPs
(excitatory post synaptic potential)
= depolarizing - increase chance that neuron will fire an AP
IPSPs
(inhibitory post synaptic potential)
= hyperpolarizing- decrease chance that neuron will fire an AP / more K going out
is the opening of K channels caused by the closure of Na channels ?
NO
- when threshold is reached they both open K channels are just slower so happen second
what do inactivation gates do ?
- on sodium gated channels
- play an important role in refractory period
- prevents AP from moving backwards
how can you view channels opening and closing ?
using patch clamp recording
