membrane transport passive

Question 1

passive transport

Answer 1

no energy needed

solute travels down concentration gradient

Question 2

factors affecting diffusion rate:

1. magnitude of concentration (larger = ____ )
2. size of the molecule (larger = ____ )
3. surface area:volume ratio (shape (higher = ____ )
4. temperature (higher = ____ )
5. density of the solvent (higher = ____ )
6. solubility of solute (nonpolar = ____ )
7. distance to destination (longer = ____ )

Answer 2

1. faster
2. slower
3. faster
4. faster
5. slower
6. soluble
7. slower

Question 3

why is urea more permeable than glycerol

Answer 3

smaller

Question 4

why is tryptophan is more permeable than glucose

Answer 4

nonpolar

Question 5

transporter-mediated diffusion follows ____ order kinetics

Answer 5

1st

Question 6

simple diffusion and channel-mediated transport follows ____ order kinetics

Answer 6

zero

Question 7

facilitated diffusion: general concepts

selectivity filter:

gate:

Answer 7

selectivity filter: restricts what can pass

gate: restricts when it can pass

Question 8

ion channels:

gate ____

selectivity ____

Answer 8

yes

yes

Question 9

aquaporins:

gate ____

selectivity ____

Answer 9

no

yes

Question 10

gap junctions:

gate ____

selectivity filter ____

Answer 10

no

no

Question 11

voltage-gated ion channel:

1. ex: voltage-gated ____ channel
2. helix 4 is repeated ____ ____ ____
3. open when membrane potential ____
4. open when charged helices move toward the ____ side of the bilayer

Answer 11

1. potassium
2. hydrophobic hydrophobic lysine/arginine
3. changes
4. extracellular

Question 12

ligand gated ion channel:

example: ____ ____

operate on simliar principles as ____ ____ proteins

Answer 12

acetylcholine receptor

signal transduction

Question 13

mechanical stress gated ion channel:

environmental mechanical stresses distort the ____ or the ____ itself

used on many ____ cells

Answer 13

membrane protein

sensory

Question 14

leakage ion channels:

gate opens at ____

allows for ____ movement of ions

Answer 14

random

continuous

Question 15

gated ion channels in action:

• 5 ion channels work together to contract muscles
  
  • depolarization opens ____ ____ channels
  • exocytosed acetylcholine opens ____ ____ channels
  • local depolarization opens adjacent ____ ____ channels
  • as the depolarization spreads, ____ ____ channels open
  • coupled Ca²⁺ release channels embedded in the ____ open

Answer 15

• • voltage-gated Ca²⁺
    
    • ligand-gated Na⁺
    • voltage-gated Na⁺
    • voltage-gated Ca²⁺
    • SR

Question 16

selectivity filter examples:

1. the bacterial K⁺ channel
   
   1. distance just right for ____ H-bonds
   2. distance too far for ____ H-bonds
   3. movement results from ____ ____
2. aquaporins
   
   1. narrow: only a single file line of water ____ can fit
   2. electrostatics: H-bonding algins water molecules, ____ at narrowest point repels cations

Answer 16

1. 1. good
   2. good
   3. electrostatic repulsion
2. 1. molecules
   2. arginine

Question 17

gap junctions: ____ is the only limitation

Answer 17

size

Question 18

tight junctions

makes cells into an

Answer 18

seals gap between epithelial cells

impermeable sheet

Question 19

adherens junction

Answer 19

connects actin filament bundle in one cell with that in the next cell

Question 20

desmosome

Answer 20

connects intermediate filaments in one cell to those in the next cell

Question 21

hemidesmosome

Answer 21

anchors intermediate filaments in a cell to extracellular matrix

Question 22

actin-linked cell-matrix junction

Answer 22

anchors actin filaments in cell to extracellular matrix

Question 23

passive transport in context:

• ____ = carriers
  
  • never found in ____
  • ____ defense mechanisms
  • common ____
    
    • e.g. ____
• channels can be a cellular ____ mechanism

Answer 23

• ionophores
  
  • humans
  • bacterial
  • antibiotics
    
    • valinomycin
• defense