Active Transport

All types of cells have the process of active transport.

This is the action where molecules from one highly populated area move through the membrane to a location with a lot less molecules.

The goal is to try to keep a good balance. In order for the cell to detect the population it requires a recognition of the concentration gradient.

This is where fewer molecules meet at a place where there are large numbers of molecules.

Moving from low concentration to high concentration locations is called going “against the gradient.”

Molecules need energy to accomplish active transport and they get that energy from the cell.

When the molecules have movement that doesn’t require energy it is called “passive transport.”

The process of active transport moves molecules that the cell needs such as amino acids, glucose, or ions.

Primary and Secondary Transport

For active transport there is a primary and secondary type and the difference between the two is in the type of energy used.

Primary transport is referred to as “direct active transport” because it makes use of chemical energy for moving molecules.

A standard method of using energy in the cell is through chemical energy and takes the form of ATP.

An example of primary transport is the pumping of sodium out of the cell and pumping potassium into the cell. This is called the sodium-potassium pump.

Secondary transport is referred to as “co-transport” and the energy that it uses to move molecules out or into the cell is electrochemical energy.

This process involves moving one molecule from a high concentration area into a low concentration area.

The process of the movement itself creates energy that can be used. This gives the ability to move another molecule against the gradient, in the opposite direction.

Three types of active transporters:

Due to the various requirements, there are 3 different types of active transporters that are needed:

  • Coupled transporters that link the “uphill” transport of one molecule to the “downhill” transport of a totally different molecule.
  • ATP (adenosine triphosphate)- driven pumps that make use of the energy that is stored in the ATP for molecule movement across the membranes.
  • Light-driven pumps use photon energy light for the movement of molecules across membranes. These are mostly found in specific types of bacteria cells.


In active transport it’s the proteins that are the “heavy lifters,” and each protein is very specialized.

Since active transport typically happens in moving molecules across the cell membrane, there are thousands of proteins that exist in a cell’s lipid bilayer.

They are positioned to be able to cross the membrane so that one part of the protein is on the outside of the cell and one part is on the inside of the cell.

Then they can move ions and molecules in or out of the cell. Their specialization also means that they can only move specific molecules.

As an example, a protein that moves calcium won’t be able to move glucose. Each of the cells of your body is home to hundreds of the membrane proteins.

Fun Facts about Active Transport

  • Moving molecules through the cell membrane takes them through any of the 3 main protein ports. These ports are: uniporters, symporters, and antiporters.
  • We mentioned on type of active transport, but there are actually two others. In addition to the
  • Sodium-Potassium pump, there is the Exocytosis, and the Endocytosis.
  • An example of energy being harnessed in movement can be seen in our real-life situation where water is moving through a dam. The movement creates energy that can be transformed into electricity that powers our homes. In the case of cells, the membranes can act like a kind of dam.
  • All organelles that are surrounded by membranes must be involved in concentrating some of their molecules against their concentration gradients.
  • Ions have an electrical charge and due to this they are not easy to transport across membranes. A majority of the energy that a cell expands in active transport is in pumping ions out of the cell and across the plasma membrane.
  • There are very selective transporters that exist in membranes that focus on some ions and ignore other ions.

 Interesting Facts about Biology

  • The Latin word “fungus” is a translation that means “mushroom.”
  • Believe it or not, fungi are less similar to the plant kingdom and more similar to the animal kingdom.
  • Many of our scientific words are based in Latin. The word “virulentus” is the source of our word “virus” which means “poisonous.”
  • If you cut an amoeba in half, the half that contains the nucleus will live, while the other half will die.
  • Science seems to define the term “species” as individuals that have the ability to reproduce.
  • When the body loses the ability to make certain substances that are required for life, some drugs can provide those substances. An example of this when the pancreas can no longer make insulin and causes the person to have Type I diabetes. Insulin injections can take the place of what is made in the body.

Active Transport Quiz

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