Exam I Review Flashcards

Question

Why do cells need ion potentials?

Answer 1

- Too much ENERGY needed to move a monovalent ion from water to lipid - Ions are CHARGED so can't go through hydrophobic lipid bilayer - According to BOLTZMANN distribution, probability of it happening is basically none

Answer 2

1. Membrane proteins 2. Selectivity (recognize/select particular ions) 3. Conduction (pass ions passively and rapidly - no energy needed bc going down concentration gradient) 4. Gating (open/close in controlled fashion, according to intra/extra -cellular cues)

Answer 3

Nobel prize for chem in 2003 Found structure of ion channels worked with Kcsa K+ channel

Answer 4

Historically low resolution, improved to high res in 2013 | Allowed for many channels to be discovered

Answer 5

``` Roderick MacKinnon (first discovered ion channels) Cryo-EM ```

Answer 6

Important for learning and memory

Answer 7

1. Gain better understanding of how channels work 2. Can map disease-causing mutations onto channels 3. Can study drug molecules to design better meds

Answer 8

1. Based on SELECTIVITY ``` 2. Based on GATING MECHANISMS voltage-gated ligand-gated (NTs) mechanically-gated temperature-gated gap-junctional channels (usually always open, but can be regulated; can allow ions and small molecules due to large pores) ```

Answer 9

Allow all POS ions to pass through Typically K+ and Na+, sometimes Ca2+

Answer 10

Opening/closing of channel Even LEAK CHANNELS can close All ion channels go between these 2 states

Answer 11

1. Voltage change (mostly opened by dep.) 2. Ligand binding/unbinding 3. Membrane stretch /mechanical force 4. Temperature change

Answer 12

Many channels have this stage Allows AP to be unidirectional (refractory period) I cannot be opened by stimulus

Answer 13

TTX Puffer fish toxin Na+ channel inhibitor

Answer 14

STX Shellfish toxin Na+ channel inhibitor

Answer 15

TEA K+ channel inhibitor Often used in research

Answer 16

K+ channel inhibitor

Answer 17

Ca2+ channel inhibitor

Answer 18

Heavy metal Ca2+ channel inhibitor Many heavy metals can block channels

Answer 19

Blocks nicotinic ACh receptor on NMJ

Answer 20

Snake toxin | Blocks ACh receptor

Answer 21

Local anesthetic Na+ channel inhibitor Blocks AP firing, (why you don't feel pain)

Answer 22

Local anesthetic Na+ channel inhibitor Blocks AP firing, (why you don't feel pain)

Answer 23

1. Permeability (determined by ion and channel - do they "like" each other?) 2. Ion concentration 3. Membrane voltage (higher v = more ions can pass through)

Answer 24

i = γ(Vm-Vrev) ``` γ = single-channel conductance Vm = membrane potential Vrev = reversal potential ```

Answer 25

1. Total # of channels on PM 2. Single-channel conductance (γ) 3. Single channel Po 4. Electrochemical driving force

Answer 26

Potential at which there is no net flow of currents

Answer 27

Open time: usually set threshold at 50% of amp; measure that as open time; numerical mean Open prob: make open time histogram --> use distribution to find open time, do same thing for close time

Answer 28

Sum(open times) | /total recording time

Answer 29

Different water shells Takes more energy to strip water away from Na+ than K+ (dehydration energy higher in Na ions)- this bc Na moles are smaller, ∴ water moles are able to exert stronger weight When enter selectivity filter, surrounded by AAs that form surrogate hydration (no energy cost to ion due to physical-chemical arrangement of s.f.); matches arrangement

Answer 30

When K+ ions approach, getting into pore, loses 4 H2O replaced by AA Normal arrangement: 4 above, 4 below

Answer 31

Current grows bigger w/depolarization

Answer 32

Formed by S6 segment + s.f. S4 moves in response to depolarization S4 movement pulls on S4/S5 linker S4/S5 linker causes change in S5/S6, that will open/close pore

Answer 33

chili pepper, spicy molecule

Answer 34

Cation channel, R for capsaicin Important for temp Can have lower gate and s.f. - the 2 can open/close independently

Answer 35

1 or 2 gates At different locations And s.f. can act as gate

Answer 36

Ligand binding site is far away from gate Causes wave of conformational change

Answer 37

1. Create/maintain ion gradient | 2. Uptake NTs

Answer 38

1. Transporters need ATP, channels don't 2. Transporters are slower 3. Transporters move at least ion ion Against conc.gradient, channels only conduct down

Answer 39

Channels are essential for setting up RMP If open...dissipation of ion [ ] gradient --> ∴ need TRANSPORTERS to restore gradient

Answer 40

1. Ion pumps (ATPases) Na/K pump, Ca pump, H pump 2. Ion exchangers Antiporters, cotransporters

Answer 41

Use ATP hydrolysis energy to transport ions Na/K: High Na out, high K in

Answer 42

Indirectly use ATP, use gradients to drive ions in/out (1) Antiporters - ions go against conc.gradient in diff directions (2) Cotransporters - ions go in same direction

Answer 43

Indirectly use ATP, use gradients to drive ions in/out (1) Antiporters - ions go in different directions (2) Cotransporters - ions go in same direction

Answer 44

[Antiporter] Na transported in... Exchanger uses this energy... ....to take Ca out

Answer 45

Only occurs when inside of cell becomes acidified (bc usually pH similar on both sides) Na in... Exchanger uses this energy to take ...H out

Answer 46

1. (Some) ions transported against conc.gradient 2. Requires ATP, either directly or indirectly 3. Some ion transporters are ELECTROGENIC (mem pot. can be affected by electrical activity)

Answer 47

Discovered Na/K pump

Answer 48

Originally discovered by Jens Sken Without Na/K pump - no RMP, to AP, no LIFE

Answer 49

Meaning...

Answer 50

Poison made in adrenal glands, also found in plants Drug used to treat certain types of heart failure (↑↑ pumping) Experimental effects...

Answer 51

Can bind where oubain binds and makes pump permanently active Which ions?

Answer 52

Keep intracellular [Ca2+] low | or restore concentration (working overtime)

Answer 53

Ion movement produces current Current changes voltage Membrane voltage used for signalling

Answer 54

1. Receptor potential (produced by external sensory stimuli, mainly in specialized sensory organs) 2. Synaptic potential (produced at synapses) 3. AP RP and SP are usually local voltage changes, usually passive propagation/summation

Answer 55

Local signals produced in dendrites/soma Axon hillock = trigger zone Traveling from soma to hillock = passive propogation

Answer 56

1. Magnitude 2. Time course (kinetics) 3. Propagation (depends on distance and speed)

Answer 57

Membrane properties of neuron

Answer 58

I = V/R Current = voltage/resistance

Answer 59

ΔVss = I * Rin I we control, Rin = input resistance of cell - Conductance - Size (bigger cell = bigger membrane = more channels = higher conductance = lower resistance) - Higher open prob = lower resistance 1. Channel density 2. Single-channel conductance 3. Size of cell 4. Open probability

Answer 60

g = 1/R Conductance is the inverse of resistance

Answer 61

Size-independent Resistance of a given area of membrane Factors: 1. Po 2. # of channels 3. PM conductance/resistance

Answer 62

Cell mem is a capacitor 2 conducting plates w/insulator in between The larger the capacitance, the more charges you can store If PM was just a conductor, membrane-voltage-Δ would be instantaneous; instead it is delayed

Answer 63

Water has high DC (80) | Oil has low (2)

Answer 64

Magnitude and time course greatly affect AP firing - larger capacitance = slower the response = timing/frequency would decrease - smaller capacitance = can be charged more quickly = faster response = timing/frequency would increase

Answer 65

1. # of leak channels on membrane (if current very leaky most of the current you inject will leak out) 2. Diameter (how much current can go through; charges bumping each other quickly) 3. Resistance of cytoplasm (higher resistance=more likely current is to x) Bigger SA, more channels, more leaking 4. Resistance/conductance of PM

Answer 66

Squid giant axon Sea squid cyto should be MORE conductive - Sea animal cyto has very high salt; high salt = more conductive - Larger diam - so rho (resistance) for squid axon is very low SEE NOTES

Answer 67

Resistance of 1cm^3 of cyto Constant

Answer 68

Propagates passively without activating voltage channels, ∴ subthreshold Factors: - Membrane input resistance - Capacitance (slows down mem voltage) - Time course Distance depends on - Mem properties - Size of processes (dendrites, axons) - Intrinsic properties

Answer 69

Alan Hodgkin Andrew Huxley Used electrodes to record APs on squid axon Able to completely describe biological phenomenon through math

Answer 70

We can see single-channel conductance | - Plot amplitude of currents against voltage to get i-V relationship

Answer 71

1. Cell-attached 2. Whole-cell 3. Inside-out 4. Outside-out

Answer 72

Potential at which there is no net flow of ions across membrane Refers to the fact that a change of membrane potential on either side of the equilibrium potential reverses the overall direction of ion flux

Answer 73

Producing a change in the electrical potential of a cell

Answer 74

Producing a change in the electrical potential of a cell

Answer 75

Increases heart pumping Inhibits Na/K+ pump, [Na] inside cardiac cell ↑slightly The ↑[Na] will inhibit the Na/Ca exchanger (antiporter), making it go slower; ∴ less Ca pumping out ↑ in Ca inside makes muscle contractions stronger

Answer 76

3 Na out, 2K in

Answer 77

Blocks Na/K+ pump If pump is blocked with ouabain, AP will burst sooner and faster

Answer 78

Rin= Vss / i Reflects the extent to which membrane channels are open. A low resistance (high conductance) implies many open channels, while high resistance implies many closed channels

Answer 79

Time constant A quantitative measure of how fast the membrane responds to current flow Make sure you know how to do this τ = Rin * C

Answer 80

ΔV(t) = ΔVss (1-e^(-t/τ)

Answer 81

Conduction velocity is directly proportional to nerve fiber diameter and degree of myelination (The larger the diameter of the nerve the lower the resistance there is to the flow of current along its length) The larger the fiber type diameter and the more abundant the myelin, the faster the nerve conduction velocity.

Answer 82

Lambda/length constant Mathematical constant used to quantify the distance that a graded electric potential will travel along a neuron via PASSIVE electrical conduction The greater the value of the length constant, the farther the potential will travel

Answer 83

Po increases with depolarization --> reaches max level (~80%) Overall: voltage-dependent parabola

Answer 84

Conductance increases further and further w/depolarization because more and more channels opening faster and faster

Answer 85

Diagram in notes

Answer 86

When an ion is not at its electrochemical equilibrium, an electrochemical driving force (VDF) acts on the ion, causing the net movement of the ion across the membrane down its own electrochemical gradient Vdf = Vm − Veq Push to reach equilibrium

Answer 87

RMP is -60, which is closer to Ek than Ena - this is because there are many K+ leak channels on PM and few Na Thus the membrane is many more times permeable to K+ In general, depends on: - # of channels - open probabilities

Answer 88

1. Myelination 2. Axon diameter (more diam = lower resis) 3. Extracellular K+

Answer 89

Macroglia Schwann cells in PNS Oligos in CNS (single oligo can wrap around many cells)

Exam I Review Flashcards

(125 cards)