Question

Short / Long answer type questions.
Why do most substances have to be assisted through the plasma membrane? Contrast movement by facilitated transport with movement by active transport.

Answer 1

• Plasma membrane is made up of lipid and protein, it is also a semi permeable membrane which allows the enter of some molecules and denies the entry of some molecules.
• The proteins that are present in the lipid bilayer are integral or peripheral which are used as receptors or transporters.
• These transporters are used for active and facilitated diffusion which requires energy in the form ATP and the later which does not require ATP.
• In active diffusion the molecules are transported across the membrane against their concentration gradient by the use to energy through these transporters.
• In facilitated diffusion the molecules are transported across the membrane against the concentration gradient but with the use of energy and only transporters are used. But when all the transporters in the facilated diffusion are used that is when the rate of diffusion reaches it maximum speed and after this it cannot increase.