The need for diffusion
Diffusion
Particles - molecules or ions - in a liquid and a gas are constantly moving randomly. Because of this movement, particles will spread themselves evenly throughout.
If particles of a substance are in a higher concentration compared to another area, their random movement leads to a The overall effect of something when all additions and deductions are calculated. movement of particles from this region to the region of lower concentration. This is called The movement of molecules from an area of higher concentration to an area of lower concentration..
It is important to remember that the particles:
- will move in both directions, but there will be a net movement from high to low concentration
- will end up evenly spread throughout the liquid or gas, but will not stop moving
The importance of diffusion in biology
Cells carry out chemical reactions, such as The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration. and synthesis of The dry mass of an organism.. For example, in Respiration that requires oxygen. cells need a supply of glucose and oxygen. The process also creates carbon dioxide, a toxic substance that needs to be removed from cells.
Diffusion is one of the processes that is used to get substances into and out of cells. Substances also need to enter or leave whole organisms and this often requires diffusion too.
Some examples of diffusion in biological systems
Some substances move into and out of living cells by diffusion.
In a leaf
Carbon dioxide is needed in the leaf for photosynthesis, and so diffuses into the leaf from a region of higher concentration in the air.
In the lungs
Oxygen from the air passes into the bloodstream in the lungs through structures called alveoli. It diffuses to a region of lower concentration in the bloodstream.
In liver cells
The liver breaks down excess amino acids, caused by too much protein in the diet. This produces A nitrogenous waste product resulting from the breakdown of proteins. It is excreted in urine. which is a Poisonous. substance. Urea diffuses from a high concentration in liver cells to a lower concentration in the bloodstream.
