Question

1. all of the following statements about selective permeability in reference to the plasma membrane are true except:

a) barrier that allows some materials to pass through, while others are excluded
b) cells contain membrane carriers that can open / close as influenced by cell and cell environment
c) the cell membrane lacks carriers for molecules the cell wants to keep out or keep in
d) all types of cells in the human body have the exact same membrane carriers present on their cell membranes

1. molecules will move by diffusion if:

a) the molecules are small enough to pass through the membrane’s pores or channels b) the molecules are lipid - soluble
c) the molecules are assisted by a membrane carrier
d) concentration gradient supports kinetic movement (from high to low concentration) e) all of the above

1. all the following are true regarding active membrane transport except:

a) atp is used to move substances across a membrane
b) process is used when substances are too small to travel through membrane channels

Explanation:

Question 8

• Option a describes the basic concept of selective permeability.
• Option b is correct as membrane - carriers can be regulated.
• Option c is false because the cell membrane has specific carriers for substances it wants to control.
• Option d is false as different cell types have different membrane carriers based on their functions.

Question 9

• Small, lipid - soluble molecules can diffuse through the membrane. Membrane carriers can assist in facilitated diffusion, and a concentration gradient is necessary for diffusion. So all options are correct for diffusion under different circumstances.

Question 10

• Active transport uses ATP to move substances against their concentration gradient. It is not used when substances are too small to travel through membrane channels; rather, it is used when substances need to move against the concentration gradient.

Answer:

1. C. The cell membrane lacks carriers for molecules the cell wants to keep out or keep in; D. All types of cells in the human body have the exact same membrane carriers present on their cell membranes
2. E. All of the above
3. B. Process is used when substances are too small to travel through membrane channels