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Biochemistry > Passive, facilitaed and active transport > Flashcards

Passive, facilitaed and active transport Flashcards

1
Q

The hydroPHOBIC interior of a lipid bilayer prevents the passage of most polar/nonpolar molecules?

A

polar

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2
Q

What do cells have that allows for the transfer of specific water-soluble molecules and ions across their membrane?

A

specialized transmembrane proteins

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3
Q

What are 2 of the major classes of membrane transport proteins?

A

transporters (carriers or permeases)

channels

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4
Q

All channels and many transporters allow SOLUTES to cross the cell membrane only DOWN a concentration gradient. This process is called:

A

passive transport or facilitated transport

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5
Q

In which direction do solutes cross the membrane in passive or facilitated transport?

A

down the concentration gradient

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6
Q

What drives passive transport of a single UNCHARGED molecule and determines its direction?

A

concentration of each side of the membrane

down concentration gradient = high –> low

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7
Q

What drives the transport of a solute with a NET CHARGE across the membrane?

A

concentration gradient and the electrical potential difference (aka membrane potential)

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8
Q

The concentration gradient and the electrical gradient combine to form the _______.

A

electrochemical gradient (or net driving force)

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9
Q

Type of transport that does NOT require the cell to expend energy and involves a substance moving DOWN its concentration gradient

A

passive transport

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10
Q

Sometimes solutes can moves freely across the lipid portion of the cell membrane directly. Other need assistance of membrane proteins. This process is called:

A

facilitated diffusion

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11
Q

This type of transport involves solute movement AGAINST their electrochemical gradient.

A

active transport

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12
Q

What type of transport is coupled to a source of energy, usually ATP hydrolysis or an ion gradient?

A

active transport

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13
Q

What is active transport mediated by?

A

transporters

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14
Q

Which type molecules diffuse freely across the lipid bilayer?

A

hydrophobic molecules (small, nonpolar)

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15
Q

Which molecules diffuse the fastest through the lipid bilayer?

A

small, hydrophobic (nonpolar) molecules

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16
Q

O2, N2, CO2, benzene are ____ molecules that diffuse (slowly/rapidly) across bilayer

A

hydrophobic

rapdily

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17
Q

Which molecules diffuse across the bilayer but to a much lesser extent?

A

small, uncharged polar molecules

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18
Q

Urea, water, glycerol are ____ molecules that diffuse (slowly/rapidly) across bilayer

A

small, uncharged polar

slowly

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19
Q

Which molecules have very little diffusion across the bilayer?

A

large, uncharged polar molecules

glucose, sucrose

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20
Q

Which molecules do not diffuse across the bilayer and require active transport or facilitated transport?

A

ions

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21
Q

What occurs during simple diffusion of molecules in water?

A

they spread out until there is a uniform concentration of solutes in the solvent

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22
Q

What does diffusion across an artificial lipid bilayer depend on?

A

nature of molecule

concentration

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23
Q

What does SARS-Cov2 bind to?

A

ACE2 enzyme receptor on surface of target cell

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24
Q

What happens when SARS-Cov2 binds to receptor on target cell?

A

facilitates internalization of membrane and dumps intracellular contents into cell which causes an attack on the protein machinery and replicates

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25
Q

Does water have (high/low) permeability across synthetic bilayers?

A

high = rapid diffusion

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26
Q

Do ions have (high/low) permeability across synthetic bilayers?

27
Q

Do carrier proteins mediate passive or active transport?

28
Q

how do carrier proteins mediate passive transport?

A

conformational changes (NO ENERGY)

29
Q

rate of transport is proportional to concentration of molecule being transported

A

simple diffusion

30
Q

rate of transport reaches a MAXIMUM when transport protein is saturated

A

transporter mediated

31
Q

What are the 3 ways to drive active transport?

A

coupled
ATP-driven
light-driven pumps

32
Q

transport of one molecule AGAINST a concentration gradient is COUPLED to another molecule being transported DOWN its concentration gradient

A

COUPLED active transport

33
Q

transport involved energy from ATP hydrolysis to move a molecule AGAINST its concentration gradient

A

ATP-driven active transport

34
Q

transport found in bacteria use energy from LIGHT

A

light-driven pumps

35
Q

What are the 3 types of carrier-mediated transport?

A

uniport
symport
antiport

36
Q

Type of carrier-mediated transport where a single molecule is being transported

37
Q

Type of carrier-mediated transport where there is cotransport of 2 ions and the binding of the first facilitates the binding of the second

38
Q

Type of carrier-mediated transport where there is a movement of one molecule against the concentration gradient and another ion down the concentration gradient

39
Q

What is the glucose carrier driven by?

A

Na+ gradient

40
Q

Bind of Na+ and glucose is _____, when one binds this facilitates the binding of another.

A

cooperative

41
Q

The glucose carrier is what type of carrier-mediated transport?

42
Q

What are the concentrations of the Na+/K+ pump and where are they located?

A

intracellular K+ is high

extracellular Na+ is high

43
Q

For every molecule of ATP that is hydrolyzed, how many Na+ are pumped (in/out) and how many K+ are pumped (in/out)?

A

3 Na+ out

2 K+ in

44
Q

Why does the sodium-potassium pump use ATP?

A

Na+ and K+ go AGAINST their concentration gradient

45
Q

What are the 2 types of occluding junctions?

A

tight (vertebrates)

septate (invertebrates)

46
Q

What are the 2 anchoring junctions with actin filament attachment sites?

A

cell-cell (adherens)

cell-matrix (focal)

47
Q

What are the 2 anchoring junctions with intermediate filament attachment sites?

A

cell-cell (desmosomes)

cell-matrix (hemidesmosomes)

48
Q

What are the 2 types of communicating junctions?

A

gap

plasmodesmata (plants only)

49
Q

What are the 2 types of signal-relaying junctions?

A

chemical synapses

50
Q

Mutations that lead to altered or loss of function of cadherin leads to what?

51
Q

these junctions (2) create a barrier to the movement of molecules extracellularly between cells, creating the need for intracellular and/or transcellular transport

A

tight and adherens junctions

52
Q

As the amount of Ca2+ increases, the extracellular parts of the cadherin chains become more (rigid/floppy)?

53
Q

What happens when enough Ca2+ is bound on the cadherin?

A

the cadherin dimer extends from the surface where it can bind to a cadherin dimer on a neighboring cell

54
Q

Type of junction where protein tubes composed of connexin monomers connect 2 cells by penetrating the cell membrane of 2 adjacent cells

A

gap junctions

55
Q

Type of junction that provides a fluid filled space through which materials of less than about 1,000 molecular weight can pass form one cytoplasm to the next

A

gap junctions

56
Q

What are examples of materials transported via gap junctions? (2)

A

calcium

ATP

57
Q

Do gap junctions exist in closed or open form?

58
Q

Which junctions contribute to the electrical coupling of the heart, neurons, and retinal tissues?

A

gap junctions

59
Q

Which junctions have size restrictions?

60
Q

What forms gap junctions?

61
Q

How many connexins do humans have?

A

14 (each encoded by its own gene)

62
Q

What is the most abundant cell in bone in the mineralized matrix?

63
Q

Where do osteocytes connect?

A

connect each other only at the tips of their dendrites where gap junctions are formed

64
Q

Where is the Na+ driven glucose pump located?

A

apical PM of kidney and intestinal cells

Biochemistry (9 decks)

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