Exam 3 Transport through Membranes II PASSIVE Flashcards
Digitalis and oubain bind to _ site of Na+/K+ pump to keep in locked in _ conformation
bind to allosteric site keep in E2 conformation
Factors influencing simple diffusion:
a concentration gradient of 100x vs 2x which one moves faster?
100x because the larger the magnitude of the concentration gradient more likely to flow from an area of high to low concentration
Factors influencing simple diffusion:
size of molecule likely to diffuse faster?
small travels faster and through things
Factors influencing simple diffusion:
thick or thin membrane has the ability to travel fast?
thinner because higher surface area: volume ratio
Factors influencing simple diffusion:
high or low temperature will cause faster diffusion?
high temperature
Factors influencing simple diffusion:
how does density of the solvent influence diffusion rate?
high density ie higher viscosity means more molecules in ECF which means more road blocks. High density means slower diffusion rate
Factors influencing simple diffusion:
how does solubility of the solute influence diffusion rate?
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
Factors influencing simple diffusion:
how does distance to destination affect diffusion rates/
the longer the distance means the slower the diffusion will occur
why is urea more permeable than glycerol?
although they have similar polarities (amines vs hydroxyl groups) urea is smaller and thus will diffuse at a rate faster than glycerol
why is tryptophan more permeable than glucose?
Tryptophan may be larger but has larger hydrophobicity because of its fused rings
transporter-mediated diffusion follows what order of kinetics
1st order kinetics
simple diffusion and channel-mediated transport follows what order kinetics?
zero order kinetics
what are the 2 features of facilitated diffusion?
selectivity filter (what) and gate (when)
ion channels have what features for facilitated diffusion
gate and selectivity filter
aquaporins have what features for facilitated diffusion
just selectivity filter
gap junctions have features for facilitated diffusion
neither! just a big ol’ hole
what are the 3 types of gates present in ion channels?
voltage, ligand, and stress (mechano)
what is important to note about voltage gated channels?
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
how do ligand gated channels work?
taking signal from outside and transducing it inside. Ligands bind to allosteric-ish site and undergoes conformational change
what are the 2 ways pressure act up mechanical stress gating?
- distorts membrane itself, pulls protein along it and changes its shape
- protein is tethered to cytoskeleton or ECM and those pull away and change protein’s shape
how do leakage channels work? and what does it help in resolving?
doesn’t follow the rules; allow leakage as gate opens at random how we release K+ buildup
what feature(s) does the bacterial K+ channel in bacteria use?
use selectivity filter. K+ is just right for good H-bonds (size wise vs Na+ which is too small)
how do K+ movement occur in the bacteria K+ channel?
electrostatic repulsion of positive charged ions
how do aquaporins work?
selectivity filter; no gate. Shape (narrow ie single file line of H2O molecules) and charge (H-bonding) complimentary
H-bonding in aquaporins occurs with the _
backbone of proteins
what amino acid is and the narrowest point of an aquaporin and why?
Arg; it repels cations and why H2O can pass only
how do gap junctions work?
doesn’t follow rules remember; size of the opening is the only limitation. Falls down concentration gradient high -> low)
“not all cell-cell junctions create channels” what is an example of this?
tight junctions; makes cells into an impermeable sheet and does not let anything pass
What gets through in anchoring junctions?
passes information but not in molecule form
adherens and desmosomes allow what through?
like mechanoreceptors passes sensory information on
actin-linked cell-matrix junctions and hemidesmosomes allow what through?
similar to signalling cascades; passes along information
what type of carrier is found in bacteria? and its purpose?
ionophores are a bacterial defense mechanism common in antibiotics
T/F: channels can be cellular defense mechanisms too
true
