Exam 3 Transport through Membranes II PASSIVE

Question 1

Digitalis and oubain bind to _ site of Na+/K+ pump to keep in locked in _ conformation

Answer 1

bind to allosteric site keep in E2 conformation

Question 2

Factors influencing simple diffusion:

a concentration gradient of 100x vs 2x which one moves faster?

Answer 2

100x because the larger the magnitude of the concentration gradient more likely to flow from an area of high to low concentration

Question 3

Factors influencing simple diffusion:

size of molecule likely to diffuse faster?

Answer 3

small travels faster and through things

Question 4

Factors influencing simple diffusion:

thick or thin membrane has the ability to travel fast?

Answer 4

thinner because higher surface area: volume ratio

Question 5

Factors influencing simple diffusion:

high or low temperature will cause faster diffusion?

Answer 5

high temperature

Question 6

Factors influencing simple diffusion:

how does density of the solvent influence diffusion rate?

Answer 6

high density ie higher viscosity means more molecules in ECF which means more road blocks. High density means slower diffusion rate

Question 7

Factors influencing simple diffusion:

how does solubility of the solute influence diffusion rate?

Answer 7

to transverse a lipid membrane need to get through the predominately nonpolar hydrocarbon tails. Ie need solute to me nonpolar to have higher solubility and thus higher diffusion rate

Question 8

Factors influencing simple diffusion:

how does distance to destination affect diffusion rates/

Answer 8

the longer the distance means the slower the diffusion will occur

Question 9

why is urea more permeable than glycerol?

Answer 9

although they have similar polarities (amines vs hydroxyl groups) urea is smaller and thus will diffuse at a rate faster than glycerol

Question 10

why is tryptophan more permeable than glucose?

Answer 10

Tryptophan may be larger but has larger hydrophobicity because of its fused rings

Question 11

transporter-mediated diffusion follows what order of kinetics

Answer 11

1st order kinetics

Question 12

simple diffusion and channel-mediated transport follows what order kinetics?

Answer 12

zero order kinetics

Question 13

what are the 2 features of facilitated diffusion?

Answer 13

selectivity filter (what) and gate (when)

Question 14

ion channels have what features for facilitated diffusion

Answer 14

gate and selectivity filter

Question 15

aquaporins have what features for facilitated diffusion

Answer 15

just selectivity filter

Question 16

gap junctions have features for facilitated diffusion

Answer 16

neither! just a big ol’ hole

Question 17

what are the 3 types of gates present in ion channels?

Answer 17

voltage, ligand, and stress (mechano)

Question 18

what is important to note about voltage gated channels?

Answer 18

repeated helix sequence of 2 hydrophobic w/ K or R (for positive charge). The K or R is attracted to negative charges so which ever side of the membrane has more neg ions the helix will move and kink into ‘x’ shape to open

Question 19

how do ligand gated channels work?

Answer 19

taking signal from outside and transducing it inside. Ligands bind to allosteric-ish site and undergoes conformational change

Question 20

what are the 2 ways pressure act up mechanical stress gating?

Answer 20

1. distorts membrane itself, pulls protein along it and changes its shape
2. protein is tethered to cytoskeleton or ECM and those pull away and change protein’s shape

Question 21

how do leakage channels work? and what does it help in resolving?

Answer 21

doesn’t follow the rules; allow leakage as gate opens at random how we release K+ buildup

Question 22

what feature(s) does the bacterial K+ channel in bacteria use?

Answer 22

use selectivity filter. K+ is just right for good H-bonds (size wise vs Na+ which is too small)

Question 23

how do K+ movement occur in the bacteria K+ channel?

Answer 23

electrostatic repulsion of positive charged ions

Question 24

how do aquaporins work?

Answer 24

selectivity filter; no gate. Shape (narrow ie single file line of H2O molecules) and charge (H-bonding) complimentary

Question 25

H-bonding in aquaporins occurs with the _

Answer 25

backbone of proteins

Question 26

what amino acid is and the narrowest point of an aquaporin and why?

Answer 26

Arg; it repels cations and why H2O can pass only

Question 27

how do gap junctions work?

Answer 27

doesn’t follow rules remember; size of the opening is the only limitation. Falls down concentration gradient high -> low)

Question 28

“not all cell-cell junctions create channels” what is an example of this?

Answer 28

tight junctions; makes cells into an impermeable sheet and does not let anything pass

Question 29

What gets through in anchoring junctions?

Answer 29

passes information but not in molecule form

Question 30

adherens and desmosomes allow what through?

Answer 30

like mechanoreceptors passes sensory information on

Question 31

actin-linked cell-matrix junctions and hemidesmosomes allow what through?

Answer 31

similar to signalling cascades; passes along information

Question 32

what type of carrier is found in bacteria? and its purpose?

Answer 32

ionophores are a bacterial defense mechanism common in antibiotics

Question 33

T/F: channels can be cellular defense mechanisms too

Answer 33

true