Section 1-Topic 3

Question 1

molecular gradients

Answer 1

a difference in concentration of molecules in a biological system such as individual cells, groups of cells, or an entire organism

Question 2

cell membrane

Answer 2

the barrier to water and water-soluble substances, however other molecules can still get across

Question 3

diffusion:

Answer 3

-occurs down a concn
-no medoator or involves a “channel” or “carrier”
-no additional energy

Question 4

active transport:

Answer 4

-occurs against a concn gradient
-involves a “carrier”
-requires ENERGY

Question 5

ungated:

Answer 5

determiend by size, shape, distribution of chagre, etc.

Question 6

gated:

Answer 6

voltage (ex. voltage-dependent Na+ channels)
chemical/ligand (ex. acetylcholie receptor channels)

Question 7

saturation

Answer 7

-similar to facilitated diffusion
-rate limited by Vmax of the transporters

Question 8

energetics

Answer 8

up yo 90% of cell energy expended for active transport