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Physiology > Membrane Transport > Flashcards

Membrane Transport Flashcards

1
Q

Does homeostasis = equilibrium?

A

No

  • ICF and ECF are in osmotic equilibrium
  • chemical and electrical are in disequilibrium
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2
Q

Osmosis:

A

simple diffusion of H2O through selectively permeable membrane

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3
Q

Which direction does osmosis flow?

A

from high [H2O] to low [H2O]

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4
Q

Normal osmolarity for ECF and ICF

A

300 mOsm

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5
Q

Osmolarity equilibrium:

A
  • osmolarity for ECF and ICF have to be equal

- if different, then H2O moves to fix it

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6
Q

Osmotic pressure:

A
  • amount of pressure needed to stop osmosis from happening
  • measured in mmHg
  • 1 mOsm/L = 19.3 mmHg
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7
Q

What monitors osmotic pressure in the body?

A

osmoreceptors in hypothalamus

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8
Q

Oncotic pressure:

A

osmotic pressure of plasma proteins

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9
Q

Isoosmotic can be

A

isotonic / hypotonic

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10
Q

Hyperosmotic can be

A

isotonic / hypotonic / hypertonic

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11
Q

Hypoosmotic can be

A

hypotonic

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12
Q

Tonicity:

A
  • describes volume change of a cell
  • no unit for it
  • affects steady state volume of cell
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13
Q

How is tonicity determined?

A

by # of nonpermeable ECF solutes

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14
Q

How does isotonic solution affect cell?

A

no osmosis, so no change in cell

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15
Q

How does hypotonic solution affect cell?

A

H2O moves into cell and causes swelling / lysis

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16
Q

How does hypertonic solution affect cell?

A

H2O moves out of cell and causes shriveling / crenulating

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17
Q

3 types of transport processes for molecules:

A
  • vesicular: bulk
  • passive: doesn’t need E
  • active: needs E
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18
Q

Vesicular transport:

A
  • bulk
  • moves substance across membrane w/ vesicle
  • membrane will alter to form vesicle
  • uses E by breaking down ATP/GTP
  • needs increase in intracellular [Ca2+]
  • ex: endocytosis, exocytosis, transcytosis
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19
Q

Endocytosis:

A
  • ex of vesicular transport
  • receptors regulate endocytosis
  • infolding of membrane to allow large molecule to enter the cell
  • phagocytosis: brings solids into cell (cell eating)
  • pinocytosis: brings liquid into cell (cell drinking)
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20
Q

Exocytosis:

A
  • ex of vesicular transport
  • fusion of vesicle w/ membrane to eject molecule from cell
  • needs Ca2+ and ATP
  • constitutive: product made and released immediately
  • regulated: product made and stored until signaled for release
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21
Q

Transcytosis:

A
  • ex of vesicular transport

- moves substance across cell

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22
Q

Passive transport:

A
  • doesn’t need E

- uses diffusion and osmosis

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23
Q

Diffusion:

A
  • movement of solutes from high [ ] to low [ ]

- driven by gradients until equilibrium is reached

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24
Q

Where does E for diffusion come from?

A

brownian motion: random thermal motion of atoms/molecule

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25
Q

Chemical gradient is…

A

difference in [ ] that causes net movement from higher [ ] to lower [ ]

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26
Q

Electrical gradient is…

A
  • difference in charge causes net movement

- like charges repel and unlike charges attract

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27
Q

What is the electrochemical gradient?

A

a combination of electrical and chemical gradient

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28
Q

Simple diffusion

A
  • carrier independent
  • substance moves through membrane / channel
  • lipid soluble: moves between membrane
  • non-lipid soluble: moves through membrane via channels and pores
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29
Q

T/F: simple diffusion uses active transport

A

F, uses passive transport

30
Q

Channel proteins:

A
  • transmembrane protein w/ central H2O passage / pore
  • aquaporins: H2O channels used for osmosis
  • gated ion channels: allow channel to open (permeable) /close (nonpermeable)
31
Q

Gated ion channels are classified by:

A
  • selectivity to one or more ions
  • conductance
  • rectification
32
Q

Selectivity of ions are based on:

A
  • diameter of ion
  • shape of channel
  • electrical charge of channel
33
Q

What does conductance measure?

A

measures how readily an ion moves through channel

34
Q

Rectification is…

A
  • the directional ease of movement through channel
  • inward rectifier: movement of ions into cell is easier than out
  • outward rectifier: movement of ions out of cell is easier than in
35
Q

Types of gated channels:

A
  • leak
  • voltage gated
  • ligand
  • mechanical
  • intracellular messenger
36
Q

Leak gated channels:

A
  • spontaneously open and close
  • mostly for H2O
  • high probability for opening
37
Q

Voltage gated channels:

A
  • responds to alterations in membrane potential

- change in charge polarity will cause it to open

38
Q

Ligand gated channels:

A
  • open by binding to signaling molecule

- ex: neurotransmitters, hormones, drugs

39
Q

Mechanically gated channels:

A
  • responds to physical conformation

- ex: stretch or pressure

40
Q

Intracellular messenger gated:

A
  • responds to change in intracellular signal

- ex: increase in intracellular Ca2+/cAMP

41
Q

Facilitated diffusion:

A

channel/carrier dependent (for molecules too big/polar for pores)

42
Q

Carrier proteins:

A
  • transmembrane protein w/ binding sites for molecule to be moved
  • undergoes conformational change
43
Q

Ability of carrier proteins to move molecules is affected by…

A
  • competitive inhibition
  • non-competitive inhibitions
  • saturation: not as many carriers as molecules
  • specificity: carriers are specific to molecules
44
Q

Competitive inhibtion:

A

something else attaches to binding site instead of substrate

45
Q

Non-competitive inhibition:

A

something else attaches to different area on carrier and changes shape so substrate can’t bind

46
Q

Flick’s law determines…

A
  • net movement when there’s no electrical or pressure difference
  • J=PA[C1-C2] or J= - DA[change in C/change in X]
47
Q

Net flux is inversely proportionate to…

A
  • molecular weight

- higher the molecular weight = lower speed

48
Q

Net flux is directly proportionate to…

A
  • temp: higher temp = higher brownian movement

- lipid solubility: higher solubility = higher diffusion rate b/c higher area for exchange

49
Q

What is the impact of electrical charge:

A
  • affect ions that diffuse through ion channels according to electrical/electrochemical differences
  • not accounted for by Flick’s Law
  • rate affected by # of protein channels present in membrane
50
Q

Nernst equation is used to determine…

A
  • electrochemical equilibrium potential of any ion

- also the electrical difference across the membrane where ion will reach its dynamic equilibrium

51
Q

Nernst equation:

A
  • assumes free permeability of ion

- Eion=[-61.5/z]log([ioninside]/[ionoutside])

52
Q

Diffusion trapping:

A
  • alteration of solute after it’s moved across membrane, which preserves gradient
  • allows for increased diffusion and increased rate of diffusion
53
Q

Active transport:

A
  • movement of substance across membrane against electrochemical gradient
  • needs a pump type of carrier protein
54
Q

Primary active transport:

A
  • all transported molecule are moving against the gradient

- needs pump powered by ATP

55
Q

T/F: primary active transport get E indirectly from hydrolysis of ATP

A

F, gets E directly from hydrolysis of ATP

56
Q

Secondary active transport:

A
  • uses carrier that has binding sites for two molecules
  • one molecule is moved with the gradient and drives the transport (Na+)
  • the other is linked and moves against its gradient
57
Q

Secondary active transport gets E ______ from hydrolysis of ATP

A

indirectly

- Na+ gets pumped back out of cell w/ Na+/K+ ATPase

58
Q

Types of pumps and exchangers:

A
  • uniporters
  • symporters
  • antiporter/exchanger
59
Q

Uniporters:

A
  • is a primary active transporter
  • bind and transport only one substance against gradient
  • ex: Ca2+ ATPase and SERCA
60
Q

Symporters:

A
  • binds 2+ different substances on same side of membrane
  • both move in same direction
  • secondary active transporter: one will move with its gradient and one will move against its gradient
61
Q

Symporters are also called…

A

cotransporters

62
Q

Antiporter/exchanger:

A
  • binds 2 substances from different sides of membrane
  • can use both primary and secondary active transport
  • primary: both against gradient
  • secondary: one w/ gradient and one against
63
Q

Antiporter/exchanger is also called…

A

countertransporters

64
Q

Na+/K+ ATPase

A
  • most common antiporter/exchanger
  • establishes RMP
  • primary active transport
  • 3 Na+ moves out and 2 K+ moves in
  • accounts for 1/3 of body E supply
  • decrease in activity = more positive membrane potential
65
Q

Resting membrane potential (RMP):

A
  • cellular proteins that are stuck inside cell usually have net negative charge
  • inhibits movement of cations (K+) out of cell
  • favors movement of anions (Cl-) out of cell
66
Q

Excitable cells:

A
  • nerve and muscle

- have lower RMP than non-excitable cells

67
Q

Examples of tissues that are excitable:

A
  • skeletal muscle
  • spinal nerves
  • cardiac ventricular myocytes
  • neurons of CNS
  • smooth muscle
68
Q

Factors that contribute to RMP:

A
  • difference in permeability of membrane to ions b/c of large conductance of K+ via leak channels
  • proteins trapped in cell and act as anions, which makes inside more negative
  • electrogenic pump (Na+/K+ ATPase)
  • equilibrium potential of all permeant ions (increase in permeant ions = increase in ability to force membrane)
69
Q

Membrane potential is weighted average of _____

A

equilibrium of potential of all permeant ions

- Na+, K+, and Cl- are important

70
Q

Weighting factor:

A

accounts for relative permeability of ion

Physiology (33 decks)

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