transport

Question 1

what types of molecules is the cell membrane impermeable to?

Answer 1

large and/or charged molecules

Question 2

what is the electrochemical potential of a solute?

Answer 2

partial free energy of the solute or the potential to do work when a difference in potential exists across a membrane

Question 3

what influences a solute electrochemical potential?

Answer 3

solute concentration, solute charge and valance, and the electrical potential difference across the membrane

Question 4

when do trans membrane electrical potential differences have an effect on a solute electrochemical potential?

Answer 4

when it is charged

Question 5

what is active transport?

Answer 5

movement of solute from a low electrochemical potential to a place of higher potential across a membrane (requires energy)

Question 6

what is passive transport?

Answer 6

movement of solute along its electrochemical potential gradient (no energy required)

Question 7

what is thermodynamic equilibrium? is solute exchange stopped?

Answer 7

the absence of a solute electrochemical potential difference across a membrane. There is passive solute exchange in both directions with no net transportation

Question 8

how are the goals of passive and active transport different?

Answer 8

active transport generates and maintains an electrochemical or chemical potential difference across a cell membrane while passive transport does not

Question 9

what is a non-equilibrium solute steady state and how is it maintained?

Answer 9

concentration of solutes and voltage is not the same across a membrane. maintained by active transport

Question 10

what are the three Ds of gradients?

Answer 10

difference, direction and driving force

Question 11

what are the types of passive transport?

Answer 11

diffusion, channels and uniporter carriers

Question 12

what is the difference in primary and secondary active transport?

Answer 12

primary couples movement with hydrolysis of ATP. Secondary couples movement with the passive diffusion of a second solute that drives transport (still indirectly dependent upon ATP hydrolysis)

Question 13

what are the two types of secondary active transport mechanisms?

Answer 13

symporters (move both molecules in the same direction) and antiporters (moves two molecules in different directions)

Question 14

what is the only instance of non mediated transport?

Answer 14

simple diffusion

Question 15

what is the only instance of primary active transport?

Answer 15

pumps

Question 16

what are two examples of facilitated diffusion? which is faster?

Answer 16

channels and uniporters. channels are faster

Question 17

how do uniporters transfer solute into or out of a cell?

Answer 17

they associate with a solute, undergo a conformational change and release the solute on the other side of the membrane.

Question 18

do primary active transporters have to only move one solute?

Answer 18

no, it can move two in opposite directions (ex: Na/K pump)

Question 19

what causes the gradient that is capitalized by secondary active transport?

Answer 19

primary active transport forms the gradient that it utilizes

Question 20

what is the rate of transport across a cell membrane dependent upon?

Answer 20

solute concentration on the side that the solute originates

Question 21

what is the difference in the rate of transport between simple diffusion and facilitated diffusion?

Answer 21

simple diffusion has a rate that increases linearly with increased solute. facilitated diffusion has a maximum rate and is saturable (looks like an enzyme curve)

Question 22

what is characterized by Vmax and Km in solute transportation?

Answer 22

Vmax is the maximal rate of solute transport
Km is the solute concentration when v=1/2Vmax (characterizes the afinity of solute association/disassociation with the transporter)

Question 23

what is the Vmax of a transporter controlled by?

Answer 23

the rate limiting step in the transport process and the number of transporters

Question 24

when can Vmax and Km be different for the same transporter?

Answer 24

when it is transporting different solutes

Question 25

what other aspects of enzyme kinetics apply to transporters?

Answer 25

inhibition (competitive, noncompetitive)

Question 26

what types of transporters control pH in the cell?

Answer 26

acid etruders (remove H+) and acid loaders (bring in H+)

Question 27

other than transport of H+, how is pH controlled by the cell?

Answer 27

efflux and influx of HCO3

Question 28

what is transport stoichiometry?

Answer 28

number of substrate molecules transported in one complete cycle of molecular events mediated by that protein

Question 29

how is electrogenicity achieved?

Answer 29

movement of unequal charges across the cell membrane