Transport Mechanism

                                                       Transport Mechanism                                         

Transport Mechanism - Passive

Passive transport is diffusion across cell membrane that does not require energy. It is dependent on the permeability of the cell membrane. 

Type: 

•   Diffusion- Simple diffusion means that the molecule can pass directly through the cell membrane. Diffusion is the movement of material from an area of high concentration of that substance to a lower concentration area of that substance. ex : O2 and CO2
•      Facilitated Diffusion- facilitated diffusion utilizes cell membrane protein channel to allow charged molecules to freely diffuse in and out of the cell. Ex: water
•        Osmosis- Osmosis is a special case of diffusion involving water molecules. Water molecules move from area of high concentration through a selectively permeable membrane.

Water potential: The ability and tendency for water molecule to move from one place to another is known as water potential. And the symbol for water potential is the greek letter “Ψ”. Because of its nature to dilute, water always move from an area of high water potential to a low water potential area. Just like what we can see when water in an area with high water potential move toward the low water potential area to try help dilute material like, sugar for instance.

Pressure Potential: The movement of water from a high to a low concentration gradient can be prevented or slowed down by the increasing level of pressure in the low concentration gradient solution, since pressure increases the water potential.

•   Filtration- Filtration is the movement of solute molecules and water across a membrane by normal cardiovascular pressure. The size of the membrane pores indicate which molecules may pass. Some function of the liver and kidney are based upon filtration

Transport Mechanism – Active

Active transport is the process by which dissolved molecules move across a cell membrane from a lower concentration to a higher concentration. Which mean that the molecule move against the concentration gradient, therefore they need an input of energy from the cell (Adenosine Triphosphate)(ATP)

Bulk Transport: The movement of macromolecules such as protein and polysaccharides into or out of the cell. There are two types of bulk transport, exocytosis (going out) and endocytosis (going inside); and both require the help of energy (ATP)

•          Exocytosis: is the process by which materials are removed from the cells. For Example: the secretion of digestive enzyme, where vesicle from the Golgi apparatus carry the enzyme to the cell surface, bind it and finally release their content.
•           Endocytosis: Is the reverse of exocytosis and involves the swallow up of material by the cell to form a small sack inside the cell