Active transport consumes energy and it takes place in two phases.
Active transport consumes cell energy as the molecules are transported against their concentration gradient. There are two types of active transport. They are primary active transport and secondary active transport. In this article we shall discuss active transport examples.
Examples of Primary active transport:
Examples of secondary active transport:
Sodium potassium pump:
This is the most important pump in human beings where the sodium ions (Na+) and potassium (K+) ions are transported in contrast against their concentration gradient. For the completion of every cycle of the pump three sodium are exchanged (out) against two potassium ions (in). The ATP molecule gets bound to three sodium molecules and hydrolyzed by Na+- K+ ATPase. ATP molecule gets phosphorylated and release sodium ions to outside of the cell and bring potassium ions into the cell.
Proton pump:
Proton pump is the important cycle primary active transport. It enhances the transportation of H+ ions mainly in stomach. It usually takes place in mitochondrial cell especially on the stomach surface where the protons are transported from low concentration gradient and generates electrochemical gradient at the cell membrane. Proton pump also utilises ATP molecule and hydrolysed by the enzyme called H+, K+– ATPase.
The proton pump is activated by the intracellular secondary messengers. In proton pump H+ ions are transported into or out side of the cell.
Calcium pump:
Calcium pump is usually occurs in muscle cells. In this pump the calcium ions are transported to out of the cell to reduce the calcium ion gradient around actin and myosin filaments. It helps not only the muscle relaxation but also the development of the fertilized egg.
Calmodulin is the main protein in the generation of cell signaling in the calcium pump. Calcium-ATPase plays a key role in this pump. By using this cycle the cell can maintain the inner cell calcium level 10000 times lower than extracellular concentration. For every cycle two Ca+ ions are interchanged with two H+ ions.
Electro genic pump:
This is also an important pump in primary active transport. It uses energy from ATP molecules and leads to generation of net flow of charge of ions or protons across the membrane.
The two best examples of the Electro genic pump are Sodium potassium pump and proton pump.
Glucose symport:
The small intestine and proximal tubules of nephron cells usually perform glucose symport cycle. SGLT plays a key role in glucose symport pump.
Glucose symporters move glucose molecules in only one direction means that into or out of the cell membrane. This also helps in the renal glucose reabsorption.This cycle uses the energy in the form of electrochemical gradient that is released during the primary active transport.
Sodium – Calcium antiporters:
Sodium – Calcium antiport exchanges sodium and calcium ions in opposite directions means that it removes calcium from the cell and allows sodium into the cell. For one Ca+ ion three Na+ ions are exchanged per cycle.
Sodium- Calcium exchangers are most commonly seen in mitochondrial cell and endoplasmic reticulum. This also controls the cardiac potential by getting the signal it allows the influx of sodium and efflux calcium.
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Frequently Asked Questions
What is meant by a primary active transport?
The primary active transport is the enhance the movement of molecules, ions, nucleotides from low concentration gradient to high concentration gradient across the cell membrane.. It consumes cell energy in the form of ATP molecule.
Does active transport enhance the endocytosis and exocytosis?
Active transport enhances both exocytosis and endocytosis.
Exocytosis:
Exocytosis is a process of transfer of intracellular particles into extracellular fluid. This is enhanced by the fusion of vesicle with plasma membrane. This is the last step in the synthesis. The synthesised products like enzymes, lipids, proteins, antibodies and peptide hormones are transported to extracellular fluid by this process.
Endocytosis:
Endocytosis is the process of engulfing the extracellular molecules or particles into the cell by the cell membrane. It is divided into two types namely they are phagocytosis and pinocytosis.
Phagocytosis:
It is the process of taking large particles, part of cell or whole cell into the cell. The plasma membrane from pocket around the target particle and forms vacuole.
Pinocytosis:
Is the process of engulfing the particles into the cell in the form of fluids along with the particles in the fluids.
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Hi…I am Nagasrilakshmi Narne, a postgraduate in Biotechnology and English. also completed my B.Ed. I worked in Vimtalabs as a project trainee and I have work experience as a faculty of English. So I can explain topics in simple language.
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