What is active transport and examples?
- What is active transport and examples?To sustain life, many substances have to be transported in, out of, and between cells.
- In some cases, this can be achieved through passive transport that does not consume energy.
- In many cases, however, the cell has to transport something against its concentration gradient. In these cases, active transport is required.
- Active transport mechanisms require the use of the cell’s energy, mostly in the form of adenosine triphosphate (ATP).
- If a substance has to enter the cell against its concentration gradient, ie if the concentration of the substance within the cell has to exceed its concentration in the extracellular fluid, the cell has to expend energy to move the substance.
- Active transport uses specific transport proteins called pumps that use metabolic energy (ATP) to move ions or molecules against their concentration gradient.
- In both vertebrates and invertebrates, the sodium ion concentrations in the blood are about 10 to 20 times higher than in the cell. The potassium ion concentrations are the opposite, usually 20 to 40 times higher inside the cell. Such a low concentration of sodium in the cell is maintained by the sodium-potassium pump.
- There are different types of pumps for different types of ions or molecules like calcium pump, proton pump, etc.
- Features of active transport
- During active transport, molecules move from an area of low concentration to an area of high concentration.
- This is the opposite of diffusion, and these molecules are supposed to flow against their concentration gradient.
- Active transport is called “active” because this type of transport requires energy to move molecules. ATP is the most common source of energy for active transport.
- Since the molecules move against their concentration gradient, active transport cannot take place without help.
- This requires a transmembrane protein or protein complex called a transporter, which coordinates the whole process, and a source of energy like ATP.
- Any type of transport protein that transports a particular ion or nutrient into the cell binds to a molecule of its substrate on one side of the membrane, then changes its shape and releases the substrate on the other side.
- These proteins are often called “pumps” because they use energy to pump molecules across the membrane.
What are the types of Active Transport?
Types of Active Transport
Primary active transport
- The primary active transport is also known as direct active transport or uniport.
- In this process, a solute is pumped through a membrane directly against the electrochemical gradient using energy (usually ATP).
- The substances that are transported through the cell membrane by primary active transport include metal ions such as Na +, K +, Mg2 + and Ca2 +.
- An ion pump or an ion channel is required for these charged particles to pass through the membrane and be distributed throughout the body.
- Based on the transport mechanism as well as genetic and structural isomerism, four classes of ATP-dependent ion pumps are considered:
- P-class pump
- F-class pump
- V-class pump
- ABC superfamily
The P, F, and V classes only transport ions, while the ABC superfamily also transports small molecules.
- Most of the enzymes that perform this type of transport are transmembrane ATPases.
- The best-studied example of primary active transport is the Na +, K + -ATPase of the plasma membrane. Other known examples of primary active transport are the redox H + gradient-generating system of the mitochondria, the light-driven H + gradient-generating system of the photosynthetic thylakoid membranes, and the ATP-driven acid pump (H +) in the epithelial lining of the stomach. goes…
Secondary active transport
- Secondary active transport, also known as coupled transport or cotransport, uses energy to move molecules across a membrane; In contrast to the primary active transport, however, there is no direct coupling of ATP; Instead, it relies on the electrochemical potential difference created by pumping ions into/out of the cell.
- Secondary active transport moves many molecules across the membrane, resulting in the upward movement of a single molecule. A single molecule helps build the gradient necessary to allow many chemicals to move in and out of the cell.
- The energy to create an upward transport of a solute is derived from the potential energy of another solute along its concentration gradient.
- The energy gained from pumping protons across a cell membrane is often used as an energy source in secondary active transport.
- In humans, sodium (Na +) is a commonly co-transported ion across the plasma membrane, the electrochemical gradient of which is then used to activate the active transport of another ion or molecule against its gradient. In bacteria and small yeast cells, the co-transport ion is usually hydrogen.
- Sodium-calcium exchanger, SGLT2
Carrier protein for active transport
- An important membrane adaptation to active transport is the presence of specific carrier proteins or pumps to facilitate movement.
- These are the three types of proteins or transporters: Uniporter, Symporter, and Antiporter.
- A uniporter consists of a specific ion or molecule.
- A symporter moves two different ions or molecules in the same direction.
- An antiporter also carries two different ions or molecules in different directions.
- All of these transporters can also carry small, undigested organic molecules like glucose.
- These three types of carrier proteins are also found in facilitated diffusion but do not require ATP to function in this process.
- Some examples of pumps for active transport are Na + -K + ATPase, which carries sodium and potassium ions, and H + -K + ATPase, which carries hydrogen and potassium ions. Both are antiporter carrier proteins. Two other carrier protein pumps are Ca2 + ATPase and H + ATPase, which only carry calcium or only hydrogen ions.
Importance of active traffic
- Active solute transport across biological membranes, driven by electrochemical gradients (i.e., secondary active transport), plays a central role in basic cellular processes such as nutrient uptake, excretion of toxic compounds, and signal transmission.
- Active transport is one of the most common methods of uptake of nutrients such as certain sugars, most amino acids, organic acids, and many inorganic ions by unicellular organisms.
- Secondary active transport is involved in the transport of a wide variety of molecules such as ions, nutrients, vitamins, and osmolytes in higher organisms.
- Active transport enables the efficient absorption of substances important for cellular function (and some drugs that structurally contain them) and enables the selective elimination of waste products and foreign chemicals, including many drugs.
What is active transport and examples? Types Importance 77P