Is Primary Transport Active: 5 Facts You Should Know

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In this article, let’s see about Primary active transport and 5 facts about it.

The movement of a molecule from a region of lower concentration to the region of higher concentration with the help of energy is known as Active transport. Primary active transport and Secondary active transport are the two types of active transport.

How is primary transport active?

The primary transport is active as it transports all the solutes against the concentration gradient of a membrane using direct chemical energy; Adenosine triphosphate (ATP).

Primary active transport is also known as direct active transport. Sodium, potassium, magnesium, metal ions, and calcium are some of the substances that are transported by primary active transport.

There are four types of ATP-using Primary active transport systems:

  • P-type – example Na+, K+– ATPase, Calcium pump, and H+ acid pump
  • F-type – example Mitochondrial ATP synthase and Chloroplast synthase
  • V-type – example Vacuolar ATPases
  • ABC (ATP binding cassette transporter)

What is primary active transport?

The movement of molecules across the cell membrane from the region of lower concentration to the region of higher concentration with the help of energy is known as active transport.

Active transport is of two types:

Primary active transport uses chemical energy (ATP) to transport molecules; Calcium pump in muscles, proton pump of the stomach, and sodium-potassium pump are some examples.

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Primary Active Transport from Shutterstock

How does primary active transport work?

Primary active transport moves various charged molecules across the plasma membrane with the help of ion pumps or channels. The enzymes that help in primary active transport are transmembrane ATPase. The ATPase that helps the animal cell maintain cell potential is the sodium-potassium pump.

The sodium-potassium pumps maintain the membrane potential by transporting three sodium (Na+) ions outside the cell and replacing it with two potassium (K+) ions.  The movement of the ions by the pump creates a concentration and charge difference across the cell membrane. One ATP (Adenosine triphosphate) is used as an energy source for each cycle.

Steps involved in transporting ions using a sodium-potassium pump:

  1. The sodium-potassium pump contains sodium–binding sites which attract sodium ions and holds them.
  2. After the binding of three sodium ions to the sodium binding sites, the protein binds to an ATP molecule. This then splits into ADP and a phosphate molecule. The protein uses the energy released to change its shape.
  3. The binding site faces the extracellular solution and releases the three sodium ions outside the cell and at the same time, the protein’s potassium-binding site binds to two potassium ions.
  4. The protein returns to its original shape when the potassium-binding sites are full and releases the potassium ions into the cell.
is primary transport active
Sodium-Pottasium Pump from Shutterstock

Does primary active transport use a protein channel?

Primary active transport uses carrier proteins for transport but not protein channels. The charged ions require ion pumps to cross the membrane.

The secondary active transport requires channel proteins while transporting ions across the membrane.

Where does primary active transport occur in the body?

Primary active transport occurs in the plasma membrane of specific cell types like:

  • Gastric H+-ATPase – responsible for acidification of stomach contents. The HCl acid is secreted from the parietal cells of the stomach likening with the help of high-gradient ion transport.
  • Sodium-potassium –ATPase – maintains ionic gradient in cells
  • Plasma membrane calcium ATPase (PMCA) – pumps calcium ions. The calcium ions are removed from the cell in order to maintain proper cell signaling, muscle contraction, cell proliferation, and organ development.
  • Smooth endoplasmic reticulum Ca2+ ATPase (SERCA) – removes calcium from the cytosol of the cell and transports it into the sarcoplasmic reticulum which takes place during the relaxation of the muscles. The rate of movement of SERCA is regulated by phospholamban protein and calsequestrin protein. These belong to the P-type ATPase family and have 10 types of isoforms.

Conclusion:

Primary active transport moves the ions from the region of lower concentration to region of higher concentration across the cell membrane with the help of energy Adenosine tri Phosphate (ATP). It is also known as direct active transport.

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