a cell membrane is semi-permeable. meaning that it selectively chooses between what can go in and out of the cell. A door greeter is similar to this because a door greeter can tell who to allow in/out of the building they are in.
Cell membrane
Cell membrane
I use to as a door greeter?
it controls what goes in and out of the cell like a door
A door because the Cell Membrane controls what goes in and out of the cell, and so does a door. A door keeps things like wind and bugs out from coming inside, a door also saves you from losing cool air in the summer and heat in the winter.
It could be a gate. It is a gate because the door is the cell membrane. See you need to get past the cell wall before the cell membrane.
The cell membrane would be a locked door (for example) so that ONLY the people with a key can get in and the people without a key would not be able to get in.
It means that is/can be a door to a cell 'hence semi permeable membrane? (or to anything)
The structure that regulates what enters and exits a cell is the cell membrane, also known as the plasma membrane. It is a selectively permeable barrier made primarily of a phospholipid bilayer, embedded with proteins that facilitate the transport of substances. This membrane allows essential nutrients to enter the cell while keeping harmful substances out, much like a door controls access.
You could use lots of analogies. Cell membranes keep the traffic of things going on in the cell. It also keeps stuff in or out. You could say it works like screen a door. Perhaps a better analogy is that the cell membrane is like a border (between countries). The cell membrane (much like the border guards) control the traffic in and out of the cell. A fun answer could be to compare it to a Club bouncer, that allows certain people in and blocks the entrance of others. Another analogy for a cell membrane is that it is like a sieve. That is because it lets smaller particles (like water) in, while stopping bigger particles that could cause the cell harm out.
You could be referring to the cell membrane or carrier proteins. Both allow certain substances to enter cells.
An alternative to the cell wall is the cell membrane. While the cell wall provides structural support and protection in plant cells, the cell membrane controls the movement of materials in and out of the cell in both plant and animal cells.