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Cellular Physiology > Lecture 6- Membrane transport > Flashcards

Lecture 6- Membrane transport Flashcards

1
Q

Membrane Transport Importance: (5)

A
  1. ) Nutrients – move into cells
  2. ) Wastes – move out of cells
  3. ) Ionic balance
  4. ) Electrical balance (resting membrane potential)
  5. ) Regulatory molecules – certain hormones
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2
Q

~20% of all genes in E. coli are involved in

A

membrane transport

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3
Q

Types of membrane transport: (3)

A
  1. ) Simple Diffusion
  2. ) Facilitated Diffusion
    - Carrier mediated
    - Channel mediated
  3. ) Active Transport
    - Direct (1)
    - Indirect (2    )
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4
Q
  • Simple Diffusion =
  • Driven by? =
  • Always proceeds towards…
  • Diffusion across cell
  • Membranes is limited to =
A

= Movement from region of high to low concentration
= concentration gradient
…a decrease in free energy of the system (delta G < 0)
= Small, Non-polar
(Example: O2 , CO2)

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5
Q

Factors that influence diffusion rates across membranes: (3)

A
  1. ) Solute size
  2. ) Polarity
  3. ) Solute charge
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6
Q

(1. Solute size)
- ______ molecules diffuse faster
- What can freely diffuse across membranes?

A
  • Smaller

- Uncharged, non-polar molecules with MW up to ~100

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7
Q

(2. ) Polarity)
- _______ molecules diffuse faster
- The ______ the polarity the faster the diffusion

A
  • Non-polar

- lower

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8
Q

(3. ) Solute charge)
- Lipid bilayer is highly impermeable to…
- Ions are charged, therefore…
- Requires energy to…

A
  • …ions
  • …associated with a shell of hydration (water molecules attracted to the charged ion)
  • …remove the shell of hydration (break hydrogen bonds), which would be needed to allow the ion to enter into the hydrophobic layers of the membrane
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9
Q

Osmosis is…

- in a region of _____ to _____

A

…Simple diffusion of water across a semipermeable membrane

-Diffusion of H2O from region of low solute concentration to region of high solute concentration

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10
Q

2 Factors that effect rates of diffusion

A

Permeability and Concentration gradient (provides energy for movement)

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11
Q

Fick’s 1st law of diffusion..

A

…J =-D∆C/∆X

J = rate of diffusion
= flux/unit area = (amount of substance moving)(time−1)(area-1)
D = Diffusion coefficient (inherent property of the solute in a given solvent, related to particle size, solubility, & solvent viscosity)
∆C = concentration difference (C2 - C1) between positions X2 & X1
∆X = distance from X2 to X1
(note: ∆C will be a negative value)

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12
Q

Fick’s law and biological membranes

A

J =-D∆C/∆X
D is determined by the permeability coefficient (P)
∆X, membrane thickness is
Very thin (7 - 8nm)
Similar among all membranes
Essentially invariable for any 1 specific membrane
∆C can be expressed as difference in solute concentration (absolute value of ∆S) across the membrane
J can be expressed as a molar velocity per area (v)

		v = P∆S   Units = moles/(min.mm2)

Therefore, for diffusion across a biological membrane:
V is essentially determined by just 2 factors
P, permeability
∆S, difference in solute concentration

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13
Q

Membrane permeability is largely determined by these (2)

A 
Partition Coefficient (solubility in lipid vs water)
Size
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14
Q

Factors that influence diffusion rates across membranes (ions)

A

-Sphere of hydration
…Ordered water molecules that are attracted to dissolved solutes
…Prevent ionic molecules from crossing lipid bilayers (hydrophobic membranes)

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15
Q

For sphere of hydration, the ____ shell is attracted to the _____ shell through _____ bonding
…. it requires _____ energy to remove these hydration shells/ why would it be required?

A

-outer hydration
-inner hydration
-hydrogen
….. substantial/ (required for ion to enter lipid portion of membrane)

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16
Q

How do solutes that are not membrane permeable cross biological membranes?

A

Facilitated diffusion or Active transport

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17
Q

Facilitated Diffusion involves….

- the molecule still moves with concentration gradient

A

an integral membrane protein that facilitates the movement of the solute across the membrane barrier

18
Q

Facilitated diffusion can be carried out by two different types of proteins…

A

… Carrier proteins and channel proteins

19
Q

Carrier protein kinetics

- carrier proteins are _____

A
  • specific (each transporter will only transport a specific compound or group of compounds)
20
Q

Carrier protein types (2)
-______ transporter
-______ transporter
2 types for the second one

A
  • Uniport transporter
  • Coupled transport
    • Symport and Antiport
21
Q

Uniport transporter

A

– transports only a single solute

22
Q

Coupled transport – transports 2 or more solutes

** 2 different types, Symport(?) and Antiport (?)

A

– transports 2 or more solutes
** solutes transported in the same direction
solutes transported in opposite direction

23
Q

Look at slides #27-29 too many pics

A

LOOK AT THEM!!

24
Q

Channel proteins form _______ channels through the membrane

A

hydrophilic

25
Q

Channel proteins are highly…

A

… specific for a particular solute

26
Q

Channel proteins do not undergo

A

Conformational change

27
Q

Channel proteins types (3)

A

Ion channels, Porins, and aquaporins

28
Q

(1) Ion channels are ____ specific and most are _____

A
  • Highly specificity for particular ion

- Gated (open and closed states)

29
Q

Gated ion channels (3)

A
  • Ligand-gated (Ach receptor)
  • Voltage-gated (Na+ channels in neurons and muscle)
  • Mechanosensitive channels (K+ and Ca2+ channels in the heart)
30
Q

(2) Porins have ____ pores and ____ specificity

… contain ____ barrels and allow what type of molecules to pass?

A
  • large/low

….. beta/ Allow large molecules to pass, up to 5000 Da (include small proteins)

31
Q

(3) Aquaporins contain pores for….

- and have high levels in?

A

…rapid conduction of water

-High levels in tissues that rapidly conduct water – kidney tubules

32
Q

(3) Aquaporins contain pores for….

- and have high levels in?

A

…rapid conduction of water

-High levels in tissues that rapidly conduct water – kidney tubules

33
Q

Active transport requires….

- they are ____ mediated

A

…ATP (moves against concentration gradient)

- protein

34
Q

Active transport can be

A

Direct (1*) active transport, or

Indirect (2*) active transport

35
Q

Active transport performes functions (3)

A
  • Allow for the efficient uptake of nutrients
  • Allow for the elimination of wastes
  • Allow for the unequal distribution of ions across membranes
36
Q

ATPase pumps (4)

A
  • P-type
  • V-type
  • F-type
  • ABC-type
37
Q

P-type will pump…

- it is _____ phosphorylated

A

…Cations

- transiently/ inhibited by vanadate

38
Q

V-type will pump…

A

… protons (H+) into various organelles

39
Q

F-type…

Slides 41-44

A
  • Also involved in transport of H+
  • May function in reverse**

Example = FoF1 ATPase = ATP synthase in mitochondria

40
Q

Direct (1*) Active Transport
- transport is directly linked to _____

(Slide 46)

A

-ATPase function
Examples:
Calcium Pump
Na+/K+ - ATPase Pump

41
Q

Indirect (2*) Active Transport

- Transport is indirectly linked to _____

A
  • ATPase pump (indirectly linked to ATP hydrolysis)
42
Q

Indirect 2* Active transport involves (2)

** look at slide #48

A
  • ATPase pump - that establishes a concentration gradient (actually an electrochemical gradient) for one solute (usually an ion, like H+, Na+)
  • Coupled transporter protein - makes use of the solute gradient to move another substance (could be a sugar, amino acid or any other solute) against its concentration gradient.
  • Symporter or antiporter

Cellular Physiology (3 decks)

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