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VPHY 141 > 2: Membrane Transport Systems > Flashcards

2: Membrane Transport Systems Flashcards

1
Q

3 types of cell surface

A

a. apical or mucosal surface - face lumen of a tubular tract or external environment

b. basal surface - opposite to the apical side, adjacent to the blood vessels

c. lateral surface - sides facing neighboring cell where specialized structure i.e. junctional complex is found

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2
Q
  • junctions between cells that makes
    up tissues
  • serves as an intercellular communication
A

intercellular junction

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3
Q

3 parts that form the junctional complex

A

a. tight junction or Zonula occludens
b. desmosomes or Zonula adherens
c. hemi-desmosomes

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4
Q

part of the junctional complex that:
- leave no space between cells thus preventing leakage
- tie cells together
- grant strength and stability

A

tight junction or Zonula occludens

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5
Q

part of the junctional complex that:
- consists of intermediate filaments
- hold cells together

A

desmosomes or Zonula adherens

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6
Q

part of the junctional complex:
- attach cells to basal lamina
- focal adhesions

A

hemi-desmosomes

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7
Q

study the junctional complex

A

see module 2

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8
Q
  • communication junction or gap in the junctional complex
  • channel pores between cells which allow transfer of ions or molecules
  • impt to heart, smooth muscles, and epithelial cells
A

gap junction

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9
Q

movement of molecules or atoms through a membrane

A

membrane transport

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10
Q

2 factors influencing membrane transport

A

size of the molecule
solubility in oil (lipid solubility)

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11
Q

particles that can readily pass through the cell membrane

A

water, urea
O2, N2, CO2
steroid
hormones (estrogen, testosterone)

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12
Q

particles that CANNOT readily pass through the cell membrane

A

ions
polar molecules with no net charge but with electrical imbalances or with molecular mass > 100 daltons:
- sugars
- amino acids
- nucleic acids

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13
Q

in summary, CM is permeable to:

A

gases
small uncharged polar molecules

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14
Q

in summary, CM is impermeable to:

A

ions
large polar molecules

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15
Q

2 types of membrane transport

A

passive transport - down hill, from higher to lower concentration

active transport - up hill, from lower to higher concentration

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16
Q

3 types of passive transport

A

simple diffusion, facilitated diffusion, solvent drag

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17
Q
  • movement of molecules towards the concentration gradient
  • does not require ATP
  • no carrier protein
A

simple diffusion

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18
Q

8 factors affecting rate of diffusion

A

amount or concentration of solute - higher conc. difference, faster diffusion

size of molecules - smaller molecules, faster

velocity of kinetic motion (temperature) - higher temp, faster

number of channels - more channels, faster

viscosity - more viscous, slower

membrane permeability - if permeable, faster

surface area - greater surface area, faster

distance - short distance, faster

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19
Q

when will movement of solute will cease

A

if concentration gradient has been eliminated (state of equilibrium)

20
Q

formula that describes the diffusion of solute in water

A

Fick’s Law

factors involved:
- flow of solute from region1 to region 2
- diffusion coefficient of solute
- cross-sectional area through which the flow of solute is measured
- solute concentration in region 1
- solute concentration in region 2
- distance between regions 1 & 2

21
Q
  • a carrier-mediated transport system
  • carrier proteins - move substances towards their chemical or electrical gradients (down hill)
  • does not require energy (ATP)
  • faster to equilibrate
  • shows saturation kinetics
  • shows structural specificity for molecules (e.g., L-arabinose > D-arabinose)
A

facilitated diffusion

22
Q

differences in simple and facilitated diffusion

A

simple: no carrier proteins, rate depends on concentration differences, e.g., water, O2, N2, alcohol, urea

facilitated diffusion: requires carrier proteins, rate depends on concentration of substance, e.g., sugars and amino acids

23
Q

lipids are not permeable to what?

A

cations: K+, Na+, Ca2+
anions: Cl-. HCO3-
glucose (hydrophilic)
big molecules (RNA)

24
Q

explain the difference between carrier and channel proteins

A

carrier proteins: undergo a cycle of conformational changes linked to substrate binding and dissociation on opposite sides of the membrane

channel proteins: membrane-spanning water-filled pores through which substrates passively diffuse

25
Q

3 types of carrier proteins

A

uniporter
symporter or co-transporter
antiporter

26
Q
  • carrier proteins that transport only 1 substance
  • e.g., glucose transporters (GLUT)
A

uniporter

(see module for diagram)

27
Q
  • carrier proteins that move 2 or more substances
    across the cell membrane in the same direction
  • e.g., kidney-Na+/K+/2Cl-______
A

symporter or co-transporter

28
Q
  • carrier protein transport a substance in exchange with another across the membrane
  • e.g., Na-amino acid pump (SI), 3Na+/Ca2+exchanger (removes Ca from cells)
A

antiporter
(see module for diagram)

29
Q

2 types of channel proteins

A

ungated channel
gated channel

30
Q
  • pores in the CM in which ions can permeate
  • fast transport
  • e.g., H2O channel protein
A

ungated channel protein

31
Q
  • opening or closing of gate channel protein depends
    on the presence of:
A

ion
ligand
mechanical stimulus
light stimulus

32
Q

5 types of gated channels

A

voltage-gated channel
ligand-gated channel
ion-gated channel
stretch-activated channel
light-gated channel

33
Q
  • requires electrical potential across the membrane
  • present in neurons (esp. in nerve axons), fat cells, muscles
  • e.g., Na (tetrodotoxin in puffer fish and local anesthetics), K, and Ca channels
A

voltage-gated channel

(see module for diagrams please)

34
Q
  • _______ (neurotransmitter) binding to extracellular part of the channel to allow passage of ions
  • present in neurons (esp. dendrites and cell body)
  • e.g., GABA gated Na channels, acetylcholine-gated Na channel

GABA - gamma amino butyric acid

A

ligand

a: ligand-gated channel

35
Q
  • ion-selective
  • present in different cells
    e.g., liver cells, kidney cells
A

ion-gated channel

(see module)

36
Q
  • responds to mechanical forces or pressure
  • present in skin and ear
A

stretch-activated channel

37
Q
  • present in the retina (rods)
  • channels for rhodopsin
A

light-gated channel

38
Q
  • requires carrier proteins for up hill transport
  • requires energy (hydrolysis of ATP)
    e.g., Na+-K+ pump, Ca pump
A

active transport

39
Q

normal Ca ion concentration in muscle cells:

Ca ion concentration in contracted muscle cells:

A

10^-7 M

10^-3 M

40
Q

what happens when Ca ion concentrations remain high?

what about when Ca ion concentration is low to normal?

A

high: skeletal muscle remains contracted
low: muscle relaxation occurs

41
Q
  • solvent flows in one direction (bulk flow)
  • tends to drag along some molecules of solute
A

solvent drag

42
Q

2 types of transport processes of macromolecules

A

exocytosis
endocytosis

43
Q
  • release of proteins in secretory granules or vesicles
  • membrane of secretory vesicle becomes part
    of the cell membrane
  • e.g., hormones, proteins
A

exocytosis

(see module for diagram)

44
Q
  • entry of substances or organisms inside the cell
A

endocytosis

45
Q

2 types of endocytosis

A

phagocytosis (cell eating) - bacteria, dead tissues, food particle
pinocytosis (cell drinking) - substances in solution

VPHY 141 (5 decks)

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