Expert: Walter Hintz - 2/9/2007

Question
Can you please explain to me the forces behind active transport and perhaps an example of this?

Answer
Hi Kim
Your subject is passive transport and your question is active transport so I will discuss both.  Diffusion is the movement of molecules from an area of high concentration to an area of lower concentration and transport involves a membrane.  Transport from high to low is passive transport and no energy is expended.  When the movement is from low to high it is called active transport and energy from ATP is required. When the concentrations are uneven on the cell membrane a concentration gradient occurs.  Passive transport occurs with the gradient and active transport occurs against the gradient.  The movement of Sodium across a nerve membrane involves active transport. That is why you are using energy while Reading this.