Difussion is the spreading out of particles of any substance, in a solution or gas, resulting in an overall movement from a higher concentrated are to a lower concentrated area.
The rate of diffusion is affected by the difference in concentrations, the temperature and the available surface area.
Dissloved substances such as glucose and urea and gases like oxygen and carbon dioxide move in and of cells by diffusion.
1 of 4
Osmosis
Osmosis is a special case of diffusion. It is the movement of water from a dilute to more concentrated solution through a permeable membrane that allows water to pass through.
Differences in the concentrations of solutions inside and outside a cell cause water to move into or out of the cell by osmosis.
Animal cells can be damaged if the concentration outside the cell changes dramatically.
Osmosis is important to maintain turgor in plant cells.
There are a variety of practical investigations that can be used to show the effect of osmosis in plant tissues.
2 of 4
Active Transport
Active transport moves substances from a more dilute solution to a more concentrated solution.
Active transport uses energy released from food in respiration to provide the energy required.
Active transport allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil.
Active transport enables sugar molecules used for cell rspiration to be absorbed from lower concentrations in the gut into the blood where the concentration of sugar is higher.
3 of 4
Exchanging Materials
Single-celled organisms have a relatively large surface area to volume ratio so all neessary exchanges with the environment take place over this surface.
In multicellular organisms, many organs are specialised with effective exchange surfaces.
Exchange surfaces usually have a large surface area and thin walls which give short diffusion distances. In animals, exchange surfaces will have an efficent blodd supply or, for gaseous exchange, be ventilated.
Comments
No comments have yet been made