Passive, Facilitated, and Active Transport

Question 1

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

Answer 1

polar molecules

Question 2

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

Answer 2

transmembrane proteins

Question 3

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

Answer 3

transporters (carriers or permeases) and channels

Question 4

passive/faciliated diffusion

Answer 4

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

Question 5

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

Answer 5

concentration

high to low

Question 6

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

Answer 6

concentration gradient

electrical potential difference

Question 7

the concentration gradient and the electrical gradient combine to form the

Answer 7

net driving force/electrochemical gradient

Question 8

smaller, hydrophobic molecules diffuse — across a bilayer

Answer 8

faster

Question 9

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

Answer 9

diameter

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

Question 10

energy used by carrier proteins (3)

Answer 10

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

Question 11

electrochemical gradient

Answer 11

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

Question 12

carrier proteins mediate passive transport via

Answer 12

conformational changes

Question 13

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

Answer 13

concentration of molecule being transported

Question 14

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

Answer 14

saturated

Question 15

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

Answer 15

enzyme:substrate kinetics

Question 16

3 ways to drive active transport

Answer 16

coupled
ATP driven
light driven pumps

Question 17

light driven pumps

Answer 17

found in bacteria and use energy from light

Question 18

3 types of carrier mediated transport

Answer 18

uniport
symport
antiport

Question 19

glucose carrier is driven by

Answer 19

Na+ gradient

Question 20

glucose symport carrier mechanism

Answer 20

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

Question 21

Na+ and K+ intracellular concentrations

Answer 21

intracellular K+ is high and intracellular Na+ is low

Question 22

these concentrations are maintained by the

Answer 22

Na+/K+ pump

Question 23

for evert molecule of ATP that is hydrozyled,

Answer 23

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

Question 24

importance of ATP in the Na+/K+ pump

Answer 24

phosphorylate the aspartic acid residue

leads to binding and conformational change of the pump

Question 25

types of occluding junctions (2)

Answer 25

tight junctions (vertebrates)
septate junctions (invertebrates)

Question 26

anchoring junctions with actin filament attachment sites (2)

Answer 26

cell-cell junctions (adherens junction)

cell-matrix junctions (focal adhesions)

Question 27

anchoring junctions with intermediate filament attachment sites

Answer 27

cell-cell junctions (desmosomes)

cell-matrix junctions (hemidesmosomes)

Question 28

communicating junctions (2)

Answer 28

gap junctions

plasmodesmata (plants only)

Question 29

signal-relaying junctions (1)

Answer 29

chemical synapses

Question 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

Answer 30

intracellular junctions

Question 31

E-cadherin location

Answer 31

epithelia

Question 32

N-cadherin locations (5)

Answer 32

neurons, heart, skeletal muscle, lens, fibroblasts

Question 33

P-cadherin locations (3)

Answer 33

placenta, epidermis, breast epithelium

Question 34

VE-cadherin location

Answer 34

vascular endothelial cells

Question 35

tight junctions and adherens junctions crease.

Answer 35

barrier to the movement of molecules extracellularly bretweencells

Question 36

this creates the need for

Answer 36

intracellular and/or transcellular transport

Question 37

transcellular transport

Answer 37

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

Question 38

cadherins require

Answer 38

Ca+

Question 39

low Ca+

high Ca+

Answer 39

cadherins dont do much, limp

cadherins stiffen and induce binding of cadherins

Question 40

gap junctions are protein tubes composed of

Answer 40

connexin monomers

Question 41

gap junctions connect two cells by

Answer 41

penetrating the cell membranes of two adjacent cells

Question 42

this provides a fluid filled space through which materials of less than about —- molecular weight can pass from one cytoplasm to the next

Answer 42

1,000

Question 43

examples of materials transported via gap junctions are (2)

Answer 43

calcium

ATP

Question 44

gap junctions contribute to the electrical couples of the (3)

Answer 44

heart
neurons
retinal tissues

Question 45

hereditary mutations in specific connexin genes can cause

Answer 45

cataracts in infants or at birth, and deafness

Question 46

gap junctions can exist in the

Answer 46

closed or open form

Question 47

connexins can be either

Answer 47

homomeric or heteromeric

Question 48

the intracellular channels can be either

Answer 48

homotypic of heterotypic

Question 49

humans have – distinct connexins

Answer 49

14

Question 50

each connexin is encodes by its own

Answer 50

gene

Question 51

most cells express more than

Answer 51

one type of connexin

Question 52

2 different connexins can assemble into a

Answer 52

heteromeric connexon

Question 53

connexin hemichannels

Answer 53

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