Topic Description
- Through diffusion, Solutes automatically and passively move from high to low concentration. But, what happens if the solute concentration gradient is the opposite of what the cell needs? In other words, what if the cell needs to move materials into or out of the cell against the direction of the concentration gradient of that solute.
- This will require a specialized cell transport protein, but more importantly, the cell has to use “Cellular Energy” to move the solute. This means it is not a passive type of transport, but rather an Active Transport. The cell gets the energy from a molecule containing useable chemical energy called adenosine triphosphate, or ATP.
- Here you are can see an ATP molecule. It is made of adenosine, and 3 phosphates. When the bond between the last Two phosphates is broken, it releases a great amount of useable energy. This energy can power special proteins needed for active transport.
- These transport proteins utilize binding sites to grab and force solutes across the membrane against their concentration gradient. One of the best examples of active transport Is the sodium-potassium pump. The sodium-potassium pump pulls sodium out of the cell, and potassium into the cell, both against their concentration gradient.
- So, the sodium is at a higher concentration outside of the cell, but the cell still wants to get more sodium out, this requires energy to actively transport sodium against its concentration gradient. That same protein is actively transporting potassium into the cell, against its concentration gradient. X2
- This builds up a huge gradient potential that will ultimately enable an impulse to travel along with the cells. This is necessary for proper nerve transmission, and muscle contraction, And is a major energy consumer in the body. X2
