Question

What is the difference between diffusion and endocytosis? What are similarities?

Answer 1

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Endocytosis is a process by which cells absorb molecules (such as proteins) by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane. The process which is the opposite to endocytosis is exocytosis. [1]

http://en.wikipedia.org/wiki/Endocytosis



Diffusion describes the spread of particles through random motion from regions of higher concentration to regions of lower concentration. The time dependence of the statistical distribution in space is given by the diffusion equation. The concept of diffusion is tied to that of mass transfer driven by a concentration gradient, but diffusion can still occur when there is no concentration gradient (but there will be no net flux).

http://en.wikipedia.org/wiki/Diffusion

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Molecule Transport

Two main categories of molecule transport exist in cells, active transport and passive transport (shown below). For small molecules such as oxygen, ethanol, and carbon dioxide, the molecules could easily cross the membrane via passive transport, in the form of simple diffusion through a concentration gradient. However, the means that cells use to transfer small molecules are not sufficient for transporting macromolecules, which include proteins, polynucleotides, and polysaccharides. To transport these macromolecules, cells rely on active transport. There are two basic means of active transport - by exocytosis and by endocytosis. Exocytosis involves sending macromolecules out of the cell, while the opposite applies to endocytosis.

http://library.thinkquest.org/C004535/mo...

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