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BIO 202 > Transport Across Membranes > Flashcards

Transport Across Membranes Flashcards

1
Q

2 main categories of transport across membranes:

A

1) Passive Transport
2) Active Transport

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2
Q

Passive Transport

A

The diffusion of a substance across a membrane with NO energy investment

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3
Q

Types of passive transport

A

1) Diffusion
2) Osmosis
3) Facilitated diffusion

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4
Q

Diffusion

A

Transport of a solute down a concentration gradient

–> Solute goes from areas of high conc. to low conc.

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5
Q

In diffusion, all molecules move___________ but as a population move ___________

A

RANDOMLY, but as a population diffusion becomes DIRECTIONAL

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6
Q

Each substances diffuses down…

A

ITS OWN gradient

–> Unaffected by the gradient of others

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7
Q

Equilibrium

A

Molecules are still moving but concentrations remain constant

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8
Q

Osmosis

A

The diffusion of free water across a selectively permeable membrane

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9
Q

Osmosis is helpful when…

A

solute cannot diffuse through a membrane

–> H2O will then move through the membrane to attempt to dilute the more concentrated side

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10
Q

Tonicity

A

The ability of a surrounding solution to cause a cell to gain or lose water

–> Depends largely on concentration of solutes that cannot cross the membrane

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11
Q

Isotonic

A

Concentrations are ~ equal on either side of membrane

= NO NET MOVEMENT of water across membrane

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12
Q

Hypertonic

A

A solution that has > conc. of solute than other solution across a membrane

= Water moves INTO hypertonic solution

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13
Q

Hypotonic

A

A solution that has < conc. of solute than another solution across a membrane

= Water moves OUT OF hypotonic solution

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14
Q

Most animals have their cells in a ______________ extracellular fluid

A

ISOTONIC: to maintain a stable cell volume

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15
Q

Osmotic Pressure

A

The tendency for a solution to take up water when separated from pure water by a selectively permeable membrane

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16
Q

Animal Cell in Hypotonic Solution

A

= LYSED

–> Too much water entering cell causes it to swell and then burst

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17
Q

Animal Cell in Isotonic Solution

A

= NORMAL

–> Maintains proper cell volume

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18
Q

Animal Cell in Hypertonic Solution

A

= SHRIVELED

–> Too much water leaves cell causing it to shrink in on itself

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19
Q

Plant Cell in Hypotonic Solution

A

= TURGID (ideal condition) – Very firm

–> More water entering cell creates turgor pressure that pushes up against cell wall

–> Keeps plants “perky”

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20
Q

Plant Cell in Isotonic Solution

A

= FLACCID (limp)

–> Not enough water to produce the turgor pressure needed

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21
Q

Plant Cell in Hypertonic Solution

A

= PLASMOLYZED

–> Cell inside shrinks but cell wall maintains shape (too much water leaving cell)

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22
Q

Facilitated Diffusion

A

Diffusion aided by transport proteins (“to make faster”)

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23
Q

Facilitated diffusion can allow for…

A

polar/charged molecules to diffuse through a membrane using the transport proteins as a “door”

24
Q

2 types of transport proteins:

A

1) Channel Proteins
2) Shuttle/Carrier Proteins

25
Q

Channel Proteins

A

Provide hydrophilic pathways to allow for very fast diffusion

26
Q

Carrier Proteins

A

AKA Shuttle Proteins

–> Undergo a subtle change in shape that translocates molecules across a membrane

27
Q

Facilitated diffusion still…

A

MOVES DOWN CONC GRADIENT (cannot go against the gradient)

28
Q

Active Transport

A

“pumping” a solute/molecule across a membrane going AGAINST the conc. gradient

–>*Requires energy input to do so

29
Q

Active transport enables a cell to…

A

maintain internal concentrations of small solutes that differ from concentrations in its environment

30
Q

Sodium-Potassium Pump

A

Import K+ and Exports Na+

–> Cells want high conc. of K+ and low conc. of Na+

31
Q

Sodium-Potassium Pump is also known as…

A

Sodium-Potassium ATPase

(Due to hydrolysis of ATP)

32
Q

Sodium-Potassium Pump Process (4 Steps)

A

1) 3 Na+ bind to pump (INSIDE cell)

2) ATP phosphorylation of pump causes conformation change = Na+ released to environ.

3) 2 K+ bind to pump with new conform. = triggers dephosphorylation = return to old conform.

4) K+ released into cell

REPEAT

33
Q

ATP is not the only driver of active transport:

A

Membrane potential/electrochemical gradient can be coupled to transport molecules

34
Q

Membrane Potential

A

The voltage across a membrane

35
Q

Membrane potential is due to…

A

Charge differences between cytoplasmic and extracellular membrane sides

–> as a result of unequal cation/anion distribution

36
Q

If inside of cell is negatively charged (which it is), membrane potential favors…

A

the passive transport of CATIONS INTO cell

and ANIONS OUT of cell

37
Q

2 forces driving diffusion of ions:

A

1) Conc. gradient
2) Membrane potential

38
Q

Electrochemical Gradient

A

The combination of the forces of conc. gradient and membrane potential acting on an ion

–> *Ions diffuse down their electrochemical gradient

39
Q

If conc. gradient and electrical forces oppose…

A

Active transport may be needed

40
Q

If conc. gradient and electrical forces align…

A

Ions diffuse down electrochemical gradient

41
Q

Electrogenic Pump

A

Transport protein that generates voltage across a membrane through the active transport of ions

42
Q

Electrogenic pumps help to store…

A

ENERGY –> Through generation of the voltage

–> This energy can be tapped for cellular work

43
Q

Co-transport

A

Couples favorable movement of one molecule down its conc. gradient and unfavorable movement of another molecule down its conc. gradient

44
Q

Co-Transport Example with Sucrose

A

1) H+ it pumped across membrane creating positive charge and high conc. on one side

2) H+ diffuses back through a co-transporter in which sucrose follows along

3) Sucrose is now across membrane

45
Q

Co-Transporter

A

Transport protein that couples the transport of molecules

46
Q

2 main types of active transport:

A

1) Co-transport

2) Bulk transport

47
Q

Bulk Transport

A

A category of transport of large quantities of materials/large molecules/particles across a membrane

48
Q

Types of Bulk Transport

A

1) Exocytosis
2) Endocytosis
a. Pinocytosis
b. Phagocytosis
c. Receptor-mediated endocytosis

49
Q

Exocytosis

A

Process of cells secreting (excreting) certain molecules by fusion of vesicles with the plasma membrane

(which causes materials inside to release out of cell)

50
Q

Endocytosis

A

The taking in of molecules and particulate matter by forming new vesicles from the plasma membrane

51
Q

Phagocytosis

A

The engulfing of a particle (usually food) by extending membrane around it and packaging it within a membranous sac called a food vacuole

(NON SPECIFIC)

52
Q

Pseudopodium

A

The membrane extension in phagocytosis

53
Q

Pinocytosis

A

The engulfing of liquid droplets by infolding part of the membrane to form “pits” that pinch into the cell as a vesicle

(NON SPECIFIC)

54
Q

Clathrin

A

AKA Coat Protein

–> Coats the membrane (on cytoplasmic side) that then form coated vesicles when pinched into cell

55
Q

Receptor-Mediated Endocytosis

A

SPECIFIC engulfing of substances due to receptors embedded in plasma membrane

(vesicle formation process is similar to pinocytosis)

56
Q

Receptor-mediated endocytosis is the…

A

main type of transport of macromolecules across a membrane

57
Q

Pinocytosis and phagocytosis are…

A

NON SPECIFIC

BIO 202 (33 decks)

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