Electrochemical gradients Because ions carry a charge (positive or negative) their transport across a membrane is governed not only by concentration gradients across the membrane but also by differences in charge across the membrane (also referred to as membrane potontia) Together, the conoentration (chemical) gradient and the charge difforence (electrical gradient) across the plasma membrane make up the electrochemical gradient. consider the plasma membrane of an animal cell that oontains a sodium potassium pump as wel as two non-gated (always open) ion channelse a Nat channel and a K channel. The effect of the sodium potassium pump on the concentrations of Na and K as well as the distribution of charge across the plasma membrane is indicated in the figure below. Outside cell channel (Nat) high K 1 high inside cel which of the following statements correctly describes) the driving forces for diffusion of Na and K ions through their respective channels? a. The diffusion of Na ions into the cell is facilitated by the Na concentration gradient across the plasma membrane. b. The diffusion of Na" ions into the cell is impeded by the electrical gradiont across the plasma membrane c. The diffusion of K ions out of the cel is impeded by the KT concentration gradient across the plasma membrane.

Explanation:

Cells differ in the concentration of Na+  and many other chemicals inside and out side of the cell, so diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the membrane.

The diffusion of K+ ions out of the cell is also prevented by the electrical gradient across the plasma membrane.

In the cell, the electro chemical gradient is larger for Na+ than for K+ and many other substances.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.

they are both synthetic elements

explanation:

d