Block 2 Lecture 20 Flashcards
(26 cards)
what are the similarities between carriers and channels
- both are integral membrane proteins
- both move molecules across membranes
what is the difference between carriers and channels
all channels and only some carriers can net transport down the electrochemical gradient
what happens to saturability at low concentrations
transport increases in almost direct proportion with increase in [S]
what happens to saturability at high concentrations
changes in x do not correlate with changes in y, it is zero order
what is Jmax
the maximum rate or carrier-mediate transport
how do you calculate Jmax
number of transporters times the turnover number
what is the michaelis menten equation
- the relationship between substrate concentrations and the rate of transport
- J = Jax [S]/Kt + [S]
what is Kt
a constant and is equal to the substrate concentration that produces half maximal transport
-michaelis constant
what is J
the rate of transport at a substrate concentration equal to [S]
what is the Eadie-Hofstee equation
J = -Kt (J)/[S] + Jmax
what is selectivity
the translocation of substrate from one side of the membrane to the other that is mediated by a carrier involves the transient binding of the substrate to a site or surface on the carrier
what is competitive inhibition
competition between substrates for a common carrier binding site
what happens as a result of competitive inhibition
- rate of substrate transport will be reduced
- if substrate concentration is increased, the normal maximal rate of transport (Jmax) can be achieved
what happens to Jmax and Kt as a result of competitive inhibition
an increase in Kt and no change in Jmax
what happens as a result of noncompetitive inhibition
no matter how much substrate you add it cannot prevent the noncompetitive inhibitor from binding making fewer transporters but any transporter not bound to an inhibitor is completely normal
what happens to Jmax and Kt as a result of noncompetitive inhibition
decrease in Jmax and no change in Kt
what is noncompetitive inhibtion
there are binding sites for the inhibitor is separate from the active site where the substrate binds
what is Jmax a measure of
the capacity of a transporter to move substrate
what is Kt a measure of
the extent to which transport capacity is actually realized under physiological conditions
what does a change in Jmax indicate
a change in the number of transporters
what does a change in Kt indicate
a change in the structure of a protein
what are the two categories of carrier mediated transport
- process that can only support net movement of substrate molecules down their electrochemical gradient
- those than can support net movement of substrate molecules against their electrochemical gradient
what is facilitated diffusion
a process that cannot support net transport of substrate against an electrochemical gradient
what happens with the facilitated diffusion of glucose (3 points)
- at steady state the maximum concentration of glucose that is achieved in the cell is the same as the concentration outside
- involved shape of course uptake begins at first order where y depends on x but when influx = efflux the graph is zero order
- this actually is an example of equilibrium because once influx = efflux there is no inwardly directed glucose gradient anymore
