Passive Diffusion Across Membranes

Question 1

What proteins move molecules using a concentration gradient? What is it called?

Answer 1

Facilitated diffusion:
Ionophores
Ion Channels
Transporters

Question 2

What proteins move material against a concentration gradient? What is it called?

Answer 2

Active transport:
H+ ion, or other ion types of concentration gradients.
ATP-dependent transport: (P-type ATPase, ABC transporters)

Question 3

What proteins transfer information across the membrane? Only 2 examples covered.

Answer 3

Insulin receptors
G-Protien coupled receptors

Question 4

Crossing a membrane must be energetically favorable: a concentration gradient can drive transport. What is the equation? And how do cells use this system to their advantage?

Answer 4

Reminder: any log of a number less than 1 is negative!

Question 5

We know crossing a membrane must be energetically favorable, and we know the equation that goes along with it.
If the molecule is charged, and there is an electrostatic potential difference across the membrane, this equation changes . What changes about the equation?

Answer 5

Z= Charge of particle that we’re concerned with
F= Constant (Fardays constant)
V= potential difference between side two and side one.

Question 6

To cross a membrane, a molecule must be permeable to the lipid bilayer. What is the equation that will define the rate of which a molecule will cross a membrane?

Answer 6

P= permeability of membrane
C= concentration
J= rate

Question 7

Even though water is polar how come it is able to go into the cell at a relatively high rate (without aquaporins).

Answer 7