Why the cell membrane described as being a "selective barrier"?

Question

Why the cell membrane described as being a "selective barrier"?

Answer 1

As it only allows certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion."

The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry.

Answer 2

A cell membrane's function is not only to separate the inside of the cell from the outside, but also to police hat comes into and leaves it.  A cell membrane is termed selective as it will only allow certain things through it.  As I am sure you are aware, the membrane is made up of chiefly a phospholipid bilayer.  Interspersed within this bilayer are ion channels, glycoproteins etc which selectively allow things to enter the cell.  Take water for example.  As the outerlayer of the membrane is lipid in nature, water would struggle to enter due to its differing polarity (oil and water don't mix).  One of the membrane proteins contained within the membrane are aquaporins.  These protein channels will allow water to enter and exit but not the ions.  The many other proteins will selectively allow other substrates to enter and leave.

Answer 3

Okay, just started micro-organisms this week, but lets see.

The cell membrane is made of fat molecules and protien molecules.  This arrangement allows the cell to select which molecules should enter or leave.  ie-in-water, oxygen.  out-excess water and wastes.

Answer 4

it is termed as selectively permeable because it does not allow all things to pass through it. hence only selected ions and molecules are allowed to pass through.

i hope i was able to answer your question :D

Answer 5

This just means that the cell membrane is what we humans call "picky" or a "picky eater". The cell membrane does not allow just anything to pass through (and im sure you can figure out why). It is sort of a protective way of discriminating against possibly harmful products or things that it can not contain. The cell membrane is selective by size, shape, and orientation.

Answer 6

cell mem. is desc as selective barrier cuz it doesnt allow everythng to move in or move out of da cell bt it does it selectively by judging wats gud n wats not..!!

Answer 7

becuase the cell wall is the barrier for the membrane. its on the outta egde of the ,membrane it allows H20 to enter and out agin. and the cell wall is the only barrier for the memebrane