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BIOL 2030 > Ch. 12 Membrane Transport & Potential, Ion Channels, Nerve Cell Signalling > Flashcards

Ch. 12 Membrane Transport & Potential, Ion Channels, Nerve Cell Signalling Flashcards

1
Q

define ion channels

A

membrane proteins in plasma membrane transporting inorganic ions thru cell

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2
Q

how can sugars and amino acids be transported

A

thru transport proteins

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3
Q

define transporters

A

proteins with moving parts that can shift small molecules from one side of membrane to other thru conformation shape change (carrier proteins)

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4
Q

define channel proteins

A

proteins that form small hydrophillic pores allowing solutes to pass by thru simple diffusion

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5
Q

describe the plasma membrane

A

semi-permeable, blocks passage of almost all water-soluble molecules due to double layer of phospholipid

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6
Q

what does the ability of a molecule to diffuse depend on; if they can’t simple diffuse across the plasma membrane, what is required

A

polarity and hydrophobicity; transport proteins

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7
Q

what are examples of small, non-polar molecules

A

gases, steroids, hormones

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8
Q

what are examples of small uncharged polar molecules

A

water, ethanol, glycerol

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9
Q

what are examples of large uncharged polar molecules

A

amino acids, glucose, nucleosides

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10
Q

what are the main characteristics of transporter proteins

A
  • specificity
  • competition
  • saturation
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11
Q

what are the categories of transport; briefly describe each

A
  • passive (high to low therefore no energy needed)
  • active (low to high needing energy)
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12
Q

there can be specific transport proteins for cell types. one example is transporters for skeletal muscle cells using Ca+2, describe the flow of Ca+2 regarding if a pump/energy is needed

A
  • Ca ion flows from sarcoplasmic reticulum to cytosol thru ion channels
  • cell contracts
  • Ca returns to SR thru Ca pump (transporter) activated by phosphorylation
  • active process
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13
Q

glucose is able to travel thru liver cells using transporters, describe its pathway

A
  • direction depends on gluc. conc.
  • if ↑ outside liver cell and ↓ inside (after meal for EX) then gluc uses transporters to travel into liver cell
  • if ↓ outside and ↑ inside liver cell (when hungry for EX) then liver cell will breakdown glycogen and release glucose to outside of cell using transporters
  • only maintains passive pathway (along the gradient)
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14
Q

what are the types of transporters

A
  • uniport
  • symport
  • antiport
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15
Q

define uniport transporters

A

carrying only one substance

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16
Q

define symport transporters

A
  • cotransport
  • two substances in same direction
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17
Q

define antiport

A
  • countertransport
  • two substances moving in opposite directions
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18
Q

what are the types of coupled transport

A

symport and antiport bc movement of one molecule is tied to movement of the other

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19
Q

describe p-glycoprotein; where is it found

A
  • transport protein
  • found in renal tubules, microvessels (brain), GI tract
  • eliminates toxins
  • absorbs, distributes, eliminates drugs
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20
Q

thruout history, people ate poisonous foods but didn’t die. how so?

A
  • p-glycoprotein gets rid of toxins
  • overabundance of p-glyc. pumps the drug out of the body instead of absorption
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21
Q

what drug transport is responsible for multidrug resistance in cancer cells

A

p-glycoprotein

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22
Q

what does the movement of ions depend on

A

electrochemical gradient (solute concentration and membrane voltage)

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23
Q

draw pathways of strong and weak flows of ions into and out of cell

A

strong: voltage and concentration gradients work in same direction (opposite charge movement)

weak: voltage and conc gradients work in opposite directions (same charge movement)

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24
Q

how many Na and K enter or exit cell

A

3 Na out, 2 K in (net 1 Na out)

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25
Q

draw out the pathway of the Na/K pump with each step

A
  • na binds
  • pump phosphorylates itself thru ATP hydrolysis
  • p causes conformational shape change which ejects Na into extracellular space
  • K binds
  • pump dephosphorylates
  • pump returns to original conformation and K is ejected into cytosol
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26
Q

cells are able to use high concentrations of _____ on the outside of cell as potential energy

A

sodium ion

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27
Q

how are cellular processes triggered; why?

A
  • thru energy from Na+
  • if outside of cell has higher Na conc then inside it generates powerful energy force
  • at anytime the cell can make an opening in its plasma membrane allowing Na to flow inside
  • since inside of cell has net negative charge and low na conc, na rushes to go inside cell (caused by ion channels)
28
Q

describe key characteristics of ion channels

A
  • selective (selectivity filter is lined by carbonyl channel)
  • brief opening and closing
  • respond to dif stimuli
29
Q

what does ion selectivity depend on

A
  • size of channel pore (large 4 large)
  • charge of pore lining (net - conducts + ions, vice versa)
30
Q

what causes overall charge of pore lining

A

amino acids making up lining of pore

31
Q

describe the plasma membrane of a cell

A

hydrophobic, selectively permeable

32
Q

what is made when an ion channel opens

A

aqueous pore

33
Q

what are the types of ion channels; briefly describe each

A
  • voltage-gated (changes in membrane potential)
  • ligand-gated (binding of other molecules called ligands)
  • mechanically-gated (physical stimulation)
34
Q

define ligands; what are the types of ligands

A
  • stimulating molecules that cause ion channels to open/close
  • intra/extra- cellular
35
Q

give an example of a mechanically-gated channel

A

auditory hair cells have mechanical gates that open due to vibrations

36
Q

define membrane potential

A
  • electrical diff between inside and outside of cell
  • cation + and anion -
37
Q

how does electrical current occur and how is it regulated

A
  • ion flow across membrane
  • ion channels
38
Q

in what situations do cells not have a membrane potential

A

equal concentrations of +/- ions on either side of cell

39
Q

define resting membrane potential; what it is the direct result of

A
  • -20 to -200mV (neg due to inside)
  • membrane potential under steady state
  • direct result of dif in K+ ion conc. in and outside of cell
40
Q

what is the main contributor to membrane potential

A

K+ leak channels

41
Q

if K+ leak channels are present and they play a major role in membrane potential, how is it possible for the membrane potential to be zero

A

pos and neg charges balance out on both sides of cell even if K+ conc. is higher on one side

42
Q

describe K+ ion movement

A
  • down conc. gradient
  • when they travel to outside of cell, they leave - counterions unable to pass thru K+ leak channel
43
Q

what is nernst equation used for

A
  • membrane potential when ion conc on inside and outside of cell are known
44
Q

how are electrical signals thru ions transmitted

A

neurons

45
Q

draw out a neuron including nucleus, axon, terminal and axon terminal branches, body, dendrites

A

…

46
Q

describe the movement of electrical signals in neurons

A
  • stimulus causes small change in membrane potential for cell body
  • travel thru axon due to electrical excitation (action potential) b/c depolarization leads to more depolarization
47
Q

describe what happens in an action potential

A
  • stimulus: neurotransmitters bind to receptors of dendrites, bringing mem. pot. closer to zero (depolarization)
  • repeated depolarization brings cell to threshold value which triggers opening of many Na+ channels
  • Na+ flows inside cell until it reaches peak which make K+ ion channels open and Na+ channels inactivated
  • K+ ions flow outside of cell (repolar.) causing cell to become more - than rest. mem. pot. (hyperpolar.)
  • return to resting pot. and Na+ channels close
48
Q

in order for action potential to go to a cell, it must be converted to; transmitted at

A
  • chemical signal (neurotransmitter)
  • junctions called synapses
49
Q

draw out pre and post synaptic cells connected by a dendrite; include nerve terminal, membranes, synaptic cleft

A

…

50
Q

where are neurotransmitters stored

A

synaptic vesicles

51
Q

describe pathway of action potential to target cell

A

AP received by pre-synaptic nerve terminal and passes through presynaptic and postsynaptic membranes to postsynaptic cell though connection by dendrite

52
Q

neurotransmitters are released when what channels are opne

A

Ca+2 voltage gated channels

53
Q

draw out movement of NT thru resting nerve terminal to NT receptor

A

no movement bc Ca+2 channel is closed

54
Q

draw out movement of NT thru activated nerve terminal to NT receptor

A

ca+2 enters thru channel due to nerve impulse in pre-synaptic nerve terminal which makes synaptic vesicles fuse with membrane of terminal and release nt contents into cleft

55
Q

another name for neurotransmitter receptors is

A

transmitted-gated ion channels

56
Q

what happens when NTs bind to NT receptors

A

conformational shape change of NT receptor occurs which lets ions flow into post synaptic cell and change membrane potential

57
Q

draw out an active synapse

A

….

58
Q

decsribe the structure of the neurotransmitter receptor/gated ion channel

A
  • 5 similar subunit proteins arranged in a circle making a pore at the top
  • each has a binding site
  • attached to lipid bilayer on cytosol
59
Q

draw out overall, closed and open NT receptors

A

…

60
Q

describe excitatory neurons

A

release excitatory NTs which bind to receptors that make action potentials

61
Q

describe how opening of Na+ channels are excitatory

A

excitatory synapse and exc. NT bind to e/o which opens Na+ channels leading to depolarization and increases likelihood of firing action potential

62
Q

describe inhibitory neurons

A

neurons that release inhibitory NTs that bind to receptors and decrease chances of action potential made

63
Q

describe how opening of Cl- ion channels are inhibitory

A

inhibitory synapse and inhib. NT bind which keeps membrane polarized and decreases the likelihood of action potential happening

64
Q

describe GABA

A
  • gamma-aminobutyric acid
  • inhibitory NT
  • conducts Cl- ions reducing firing of AP
65
Q

how are valium and GABA gated-Cl- channels related

A
  • bind with e/o
  • makes cell more sensitive to GABA’s inhibitory action
  • enhances GABAs ability to reduce neuron firing
66
Q

why are drugs, like valium, xanax, and romazicon considered sedative

A
  • make cell more sensitive to GABAs NT in brain (release more)
  • calms and sedates person taking it (i.e. can treat anxiety)
67
Q

how can NTs on postsynaptic cell be gotten rid of

A
  • destruction by enzymes
  • reuptake
  • diffusion

BIOL 2030 (16 decks)

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