Can you explain how some substances, but not others, can pass through the cell membrane?

Question

help!

Answer 1

all cells are selecinvly permeable membrane(same thing as a semiermeable membrane) only allow certain materials to pass through the membrane. It is often related to a window screen. When you open a window, the window screen keeps unwanted material out. ex-bugs, leaves

Also, like mentioned, the size of the substance matters. If a cell wants a substance in, and it is small enough, the substance will enter the cell. This is called passive transport. Passive transport requires no energy. If a substance is too big however, then it can not pass through using passive transport. Instead the use active transport, which is where it requires energy

Answer 2

It has to do with shape and size. If a substance is small enough to fit through it will. The shape is important for fitting in the "unlock" mechanism and opening a channel.

Answer 3

it depends.
if the atom or substance is thin enough to fit through the channels of the cell. or whether or not its a nonpolar/polar phiosphilipid [spell check lol]

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phosphoc.htm

http://cellbio.utmb.edu/cellbio/membrane_intro.htm

[the second one is better picture if u scoll down a little bit]

Answer 4

well some membranes are semi permeable or selectively permeable. EX. if the membrane is hydrophilic it will let H2O through (osmosis)