a

2 1 6 Selective Permeability

what is selective permeability well

remember that the plasma membrane

surrounds all cells and it's kind of

like the bouncer at a concert the

bouncer selectively determines who comes

in and who leaves the show in order for

the show to go on and function as normal

the membrane sing similarly is

selectively permeable meaning it lets

some substances permeate or come into

the cell and it prevents others from

exiting or entering some substances can

move in and out easily these substances

include water oxygen and carbon dioxide

let's picture them with two arrows going

in and out as freely as they choose

other substances must go through protein

channels such as this one here this

these include ions such as sodium for

example which pass through through a

process called facilitated diffusion and

other other examples include large

proteins like protein hormones that need

to enter cells to activate certain

processes and some other may be larger

objects like even living organisms like

bacteria that are swallowed up by some

cells may enter the cell via vesicles

through an active transport called

endocytosis glucose for example a an

important sugar that enters cells to

create ATP in the mitochondria will

enter through transport proteins through

a process called facilitated diffusion

there's no ATP required for this process

check out our other videos

on active and passive transport to learn

more about the plasma membranes

selective permeability and its structure

and function