Passive, Facilitated, and Active Transport Flashcards

1
Q

the hydrophobic interior of a lipid bilayer prevents the passage of most

A

polar molecules

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2
Q

cells have specialized — — to transfer specific water soluble molecules and ions across their membranes

A

transmembrane proteins

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3
Q

the major classes of membrane transport proteins are known as (2)

A

transporters (carriers or permeases) and channels

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4
Q

passive/faciliated diffusion

A

channels and transporters which allow solute to cross the cell membrane down a concentration gradient

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5
Q

in the case of a single uncharged molecule, the — on each side of the membrane drives passive transport and determines its direction

A

concentration

high to low

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6
Q

in the case of a solute that carries a net charge, both its — — and — — — influence transport

A

concentration gradient

electrical potential difference

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7
Q

the concentration gradient and the electrical gradient combine to form the

A

net driving force/electrochemical gradient

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8
Q

smaller, hydrophobic molecules diffuse — across a bilayer

A

faster

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9
Q

types of molecules which can pass through channels depends on (2)

A

diameter

amino acids that make up the lining of the channel and how they interact with the molecule

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10
Q

energy used by carrier proteins (3)

A

ATP hydrolysis
mechanical energy from movement of H+ through the channel
light

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11
Q

electrochemical gradient

A

when one side of the membrane is more positively charged than the other

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12
Q

carrier proteins mediate passive transport via

A

conformational changes

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13
Q

for simple diffusion, the rate of transport is proportional to the

A

concentration of molecule being transported

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14
Q

for transporter mediated, the rate of transport reaches a maximum when transport protein is

A

saturated

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15
Q

the 1/2 Vmax and Km for carrier mediated is similar to those values for

A

enzyme:substrate kinetics

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16
Q

3 ways to drive active transport

A

coupled
ATP driven
light driven pumps

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17
Q

light driven pumps

A

found in bacteria and use energy from light

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18
Q

3 types of carrier mediated transport

A

uniport
symport
antiport

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19
Q

glucose carrier is driven by

A

Na+ gradient

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20
Q

glucose symport carrier mechanism

A

The glucose carrier in the gut oscillates between 2 states (A and B).
Binding of Na+ and glucose is cooperative; ie. when one binds this facilitates the binding of the other.
In State A the extracellular Na+ concentration is much higher than the cytosol concentration and so when Na+ binds this induces glucose to bind
When both are bound this induces a conformational change that results in the release of glucose and Na+ into the cytosol

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21
Q

Na+ and K+ intracellular concentrations

A

intracellular K+ is high and intracellular Na+ is low

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22
Q

these concentrations are maintained by the

A

Na+/K+ pump

23
Q

for evert molecule of ATP that is hydrozyled,

A

3 Na+ are pumped out and 2 K+ are pumped into the cell

24
Q

importance of ATP in the Na+/K+ pump

A

phosphorylate the aspartic acid residue

leads to binding and conformational change of the pump

25
types of occluding junctions (2)
``` tight junctions (vertebrates) septate junctions (invertebrates) ```
26
anchoring junctions with actin filament attachment sites (2)
cell-cell junctions (adherens junction) | cell-matrix junctions (focal adhesions)
27
anchoring junctions with intermediate filament attachment sites
cell-cell junctions (desmosomes) | cell-matrix junctions (hemidesmosomes)
28
communicating junctions (2)
gap junctions | plasmodesmata (plants only)
29
signal-relaying junctions (1)
chemical synapses
30
the progeny of the founder cell are retained in the epithelium by the basal lamina and by cell-cell adhesion mechanisms, including the formation of
intracellular junctions
31
E-cadherin location
epithelia
32
N-cadherin locations (5)
neurons, heart, skeletal muscle, lens, fibroblasts
33
P-cadherin locations (3)
placenta, epidermis, breast epithelium
34
VE-cadherin location
vascular endothelial cells
35
tight junctions and adherens junctions crease.
barrier to the movement of molecules extracellularly bretweencells
36
this creates the need for
intracellular and/or transcellular transport
37
transcellular transport
the movement of a molecule through a vesicle | vesicle membrane fuses with the plasma membrane to form one side of the cell to the other
38
cadherins require
Ca+
39
low Ca+ | high Ca+
cadherins dont do much, limp | cadherins stiffen and induce binding of cadherins
40
gap junctions are protein tubes composed of
connexin monomers
41
gap junctions connect two cells by
penetrating the cell membranes of two adjacent cells
42
this provides a fluid filled space through which materials of less than about ---- molecular weight can pass from one cytoplasm to the next
1,000
43
examples of materials transported via gap junctions are (2)
calcium | ATP
44
gap junctions contribute to the electrical couples of the (3)
heart neurons retinal tissues
45
hereditary mutations in specific connexin genes can cause
cataracts in infants or at birth, and deafness
46
gap junctions can exist in the
closed or open form
47
connexins can be either
homomeric or heteromeric
48
the intracellular channels can be either
homotypic of heterotypic
49
humans have -- distinct connexins
14
50
each connexin is encodes by its own
gene
51
most cells express more than
one type of connexin
52
2 different connexins can assemble into a
heteromeric connexon
53
connexin hemichannels
Osteocytes connect to each other only at the tips of their dendrites where gap junctions are formed. Osteocytes have connexin 43 hemichannels (half of a gap junction) along their cell body and dendritic processes that all movement of small molecules in and out of the cell through the lacunar-canalicular system