Need help with Plasma Membrane

[MissionCO]

Hi,

I got a exam coming up. I know all the subjects pretty well but not so much about the plasma membrane. I will tell you what I know.


Plasma membrane is made mostly of a phospholipid bilayer. Has some protein as well as cholesterol. And I think some carbohydrates (is that true?) The Plasma membrane is semi-permeable (selective). It lets some things in and keeps some things out. The major function is to protect the cell and transport of substances/molecules.

There is passive transport which requires no energy, and active transport that requires cell energy (ATP).


2 types of diffusion, simple diffusion is where substances pass through the phospholipid layer, and facilitated diffusion is when it passes through the proteins. Do I have this part correct?


Ok now here is the thing I don't really know much about. I need a good explanation on water and solutes. I know the water and solutes move from high concentrations to low. I need good definitions and examples about hypertonic solutions, hypotonic, and osmosis. It is a little confusing to me and it would be nice if you can explain to me how they work and if they require energy or not. Thanks

[shubham999]

yes, carbohydates mey be present but in small proportions and in form of mucopolysacchides etc.

types of diffusion, simple diffusion is where substances pass through the phospholipid layer, and facilitated diffusion is when it passes through the proteins. yes, its true.

osmosis is a special case of diffusion in which semi-permiable mem. is present.

if outeside a cell conc. of water is more tan inside than the solntion is said to be hypotonic . if not than hyper and if equall taen iso.

its better u read NCERT BIOLOG OF 11THJ CLASS!!!

[JackBean]

Cholesterol may not be present (e.g. in plants), but other sterols can be.
Saccharides are not exactly in the membrane, but they can be attached either to membrane proteins or the lipids.

[marquitosgm]

And those oligosaccharids are normally attached to the external side, aren't them?

[JackBean]

yep