Passive and Active Transport

Cells require many substances to ensure proper function — nutrients, oxygen, and more. But how does the cell acquire these substances? In other words, how are these substances transported?

There are two main ways particles can be transported: active and passive transport. What is the difference? Well, to understand these two terms, we must first understand the ideas of particle concentrations and concentration gradients. The concentration of particles is simply the number of particles in that area. A gradient is uneven distribution, or concentration, of particles.

Now, back to transport. Passive transport is the movement of particles without energy. Particles move from a high to low concentration along the concentration gradient. Active transport, however, is the movement of particles with energy. The particles move from a low to high concentration against the concentration gradient.

Why does active transport require energy? Well, the cell prefers to be in a state of dynamic equilibrium. That means it likes to have equal concentrations of particles on either side of its membrane. When the particles move from high to low concentrations, they are balancing the concentration gradient and reaching dynamic equilibrium. Balance is the key word here. However, when the particles move from low to high in active transport, they are creating unbalanced concentrations. The 'low' is becoming lower, and the 'high' is becoming higher. But why does it require energy? Well, in order for the particles to move from low to high concentrations, they need carrier proteins. They will not simply move on their own. It is the carrier protein that requires energy.

To read about the different types of active and passive transport, check out the other blog posts!

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