Реферат: Fermentation Photosynthesis Osmosis Essay Research Paper This

Diffusion is the mixing of the atoms or molecules of one substance

with those of another. It is caused by the natural movements of atoms

and molecules. Diffusion occurs readily in gases and liquids because of

the constant and random motion of their atoms and molecules. The

process takes place more rapidly in gases than in liquids. Molecules of

gases are farther apart and collide less frequently than those of

liquids–and collisions among molecules hinder diffusion. In solids, the

molecules are arranged in rigid patterns and move very little. Therefore,

diffusion does not occur in solids except under special conditions.

Diffusion uses energy non-stop. The use of energy is used a lot in all of

these processes.

Osmosis is the movement of liquid from one solution through a

special membrane into a more concentrated solution. The process is

essential for the survival of living things. For example, plants absorb

most of their water by osmosis. In animals, osmosis helps regulate the

flow of water and nutrients between body fluids and cells. Industries

reverse osmosis for such purposes as water purification and food

preservation.

An enzyme is a molecule that speeds up chemical reactions in all

living things. Without enzymes, these reactions would occur too slowly or

not at all, and no life would be possible. All living cells make enzymes,

but enzymes are not alive. Enzyme molecules function by altering other

molecules. Enzymes combine with the altered molecules to form a

complex molecular structure in which chemical reactions take place.

The enzyme, which remains unchanged, then separates from the product

of the reaction. Because of this, all enzymes serve as catalysts. Catalysts

are single enzyme molecules that can perform its entire function a

million times a minute. The human body has thousands of kinds of

enzymes. Each kind does one specific job. Without enzymes, a person