Chapter 3: Diffusion, Osmosis and Active Transport: Volume Ratio

Diffusion:

Is the ^^net movement of ions or molecules^^ from a region of ^^higher concentration to a region of low concentration^^ ^^down a concentration gradient.^^

Factors Affecting Rate of Diffusion:

• ^^Surface Area:^^ larger the SA faster the rate of diffusion.
• ^^Temperature^^: higher the temp faster the rate of diffusion.
• ^^Diffusion Distance^^: the greater the distance the slower the rate of diffusion.

Example of Diffusion in human body:

Is exchange of oxygen and carbon dioxide in lungs.

Osmosis:

Is the ^^movement of water molecules^^ from a solution of ^^higher water potential to a solution of lower water potential through a partially permeable membrane.^^

Terms to remember regarding Osmosis:

• %%Turgid cells%% are described as turgid when they are swollen due to a high water content inside the cell and are causing turgor pressure. (occurs in hypotonic solution).
• %%Turgor Pressure%% is the pressure on the cell wall from the cell membrane pushing upon it.
• Cell becomes %%flaccid%% when water moves out of the cell via osmosis. The cell becomes shrink but the cell membrane does not peel away from the cell wall. (occurs in hypertonic solution).
• %%Plasmolysis%% is shrinkage of cells when no or too little water is present inside.
• In an Isotonic solution neither water enters or leaves due to no concentration difference.

  ### Example of Osmosis in human body:

  Exchange of substances in kidneys.

Active Transport:

Is the process in which ^^energy is used^^ to move the ^^particles of a substance against a concentration gradient^^ from a region where they are ^^in low concentration to a region where they are in high concentration^^.

Example of Active Transport in human body:

Absorption in villi.