Transport Across Cells-A Comparison

 

There are two major ways molecules can be transported across cells. This can be either Passive or Active and while active requires the use of energy, passive does not. Passive transport requires the movement of particles from high to low concentration such as diffusion and osmosis, active transport in contrast requires the movement of particles from low to high concentration hence why energy is needed.  

Fig 1.0 Passive transport can be described as rolling a ball downhill needing less energy and active transport is pushing the ball uphill requiring hard work.

Diffusion: The movement of particles down a concentration gradient from an area of high                                       concentration to an area of low concentration until evenly distributed. A solution is required                    which includes a solute + solvent. Water is a universal solvent and sugar or salt is a good                         example of a solute.

Fig 1.1 Diffusion down a concentration gradient 

Osmosis: This is the movement of water particles in a solution from an area of  high concentration to    an area of low concentration across a selectively permeable membrane. A selectively permeable membrane or partially permeable membrane only allows  certain molecules or ions to cross it. It can be described as a sieve or filter. 

Fig 1.2 Osmosis across a selectively permeable membrane

What are some example of osmosis in living things?

Active Transport: Movement of molecules or ions across a cell membrane from a  region of lower      concentration to a region of higher concentration against the concentration gradient. This process is most seen in the sodium-potassium pump (Na+/K+ ATPase) that helps to create a resting potential in the cell using ATP.

Fig1.3 Sodium potassium pump allowing ions to flow down gradient 

 Below is a table of comparison between each processes, what are two reasons why transport processes   are important to living organisms?