Active Transport

By: Syed Quazi, Sarah Sachak, Sophia Shams

What is Active Transport?

Active transport is one of the 4 methods used by a cell to move particles across a membrane. Active transport takes place when a cell takes in more particles into it, though a high concentration is present inside. This is done by use of proteins to "pump" in more particles against the concentration gradient.
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How it works?

Active transport is carried out by globular proteins in the membrane, mostly known as pump proteins. Unlike other methods of moving particles across a membrane, passive transport. Active transport uses energy to take place, the use of ATP to activate or "pump" the particles.

  1. Molecules or particles enter the protein and reach the central chamber
  2. ATP attaches its self to the protein causing a conformational change to the protein
  3. The molecules then pass to the other side and the ATP detaches it self and becomes ADP
  4. The protein returns to its original conformational

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Active Transport of Sodium and Potassium in Axons

Axons are parts of the nerve cell that conveys messages rapidly from one part of the body to another. These nerve impulses include the rapid movement of sodium and potassium across the axon membrane. These movements occur with the help of active transport with the use of sodium-potassium protein pumps. The sodium-potassium pump uses the following a steps that pumps out 3 sodium and pumps in 2 potassium. Each cycle uses on ATP, the steps are-

  1. The interior of the pump is open to the inside axon; three sodium ions enter the pump and bind to the sites.
  2. ATP transfers a phosphate group from itself to the pump; this causes the pump to change shape and the interior is then closed.
  3. The interior of the pump opens to the outside of the axon and the three sodium ions are released.
  4. Two potassiums ions from the outside can then enter and attach to their binding sites.
  5. Binding of potassium causes release of the phosphate group; this causes the pump to change shape again so thats it is again only open to the inside of the axon.
  6. The interior of the pump opens to the inside of the axon and the two potassium ions are released; and thus the cycle repeats.

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