Primary active transport: definition and type (2023)

Have you ever wondered how your brain controls your body? How do you perceive your external environment? Well, the answer is that your brain communicates with your body. We can compare this to a telephone game, except that the participants are neurons and are relatively good at the game compared to us humans. The message delivered by neurons is sent from start to finish and is usually correct unless there is nerve damage, which can have serious consequences.

The fact that your brain and body can communicate is due to primary active transport! These processes also involve our critical ally, protein, which performs many essential functions in our bodies, from maintaining our bodies to being in famous breakfast foods like eggs. With that in mind, read on to learn more aboutprimary transportand its importance to us!

The main definition of active transport

Active transportit requires energy because the molecules must go against their concentration gradient. When a molecule goes against its concentration gradient, it goes from a low to a high concentration. This means that, for example, chloride molecules are larger inside than outside the cell, chloride needs to enter the cell to go against its concentration gradient.

Active transport needs energy because the molecules want to follow its concentration gradient, not against it.

Active transportit is a type of process that requires energy from our cells. This energy comes in the form of ATP or adenosine phosphate.

atpIt is a molecule that can provide energy to cells through a phosphate group after hydrolysis.

Molecules that follow their concentration gradient participate inpassive transport. Some common types of passive transport are simple diffusion, facilitated diffusion, osmosis, and filtration.plain diffusionit is a passive diffusion that does not require the help of carrier proteins.

transport proteinsThey are a type of transport protein that helps molecules move in and out of cells.

channel proteinsthey are transport proteins that do the same thing as transport proteins, except they diffuse the molecules faster because they don't have to change shape.

ProteinsThey are organic compounds that have a variety of functions, including acting as enzymes, antibodies, and structural components of our cells. Enzymes speed up our chemical reactions, while antibodies defend our bodies against foreign materials or antigens.

Molecules that need the help of transport proteins do so because they are polar or charged, too large to diffuse through the cell, or both. This is due to the arrangement of the cell membrane.

ocell membraneit is a structure that acts as a barrier, allowing certain things to enter and leave the cell. Transport proteins are usually incorporated into the cell membrane to assist molecules that need to enter the cell but cannot diffuse directly into the cell.

The cell membrane is made ofphospholipidsThey have a hydrophilic head and a hydrophobic tail.hydrophilicmeans water lover, andhydrophobicmeans hatred of water. Molecules that like water are polar, while molecules that hate water are nonpolar. The heads of phospholipids face out, while the tails face in, so hydrophilic molecules can't get in without the help of proteins. A detailed image of the cell membrane structure is shown in Figure 1 below.

Primary active transport: definition and type (1)Figure 1: Structure of cell membrane. Wikimedia, Lady of the Hats.

facilitateddiffusionis passive transport that requires transport assistanceproteinsas operators or channels.

Osmosis It is the passive transport of fluids, such as water, across the selectively permeable membrane of the cell.

FiltrationIt involves physical pressure that forces fluid through a selectively permeable membrane like ours.cellshave. Filtration generally refers tosangrebeing pushed through the capillary walls.

Example of primary active transport

primaryActive transportis a kind ofActive transportinvolvingatpdirectly. The sodium-potassium pump (Fig. 2) is one of the most famous examples ofActive transport.

osodium-potassium pump (Na⁺/K⁺)it is an integral part of our body while drivingnerve impulses. Nerve impulses send messages from various parts of the body to the spinal cord and brain. It allows your body to communicate with your brain, giving it useful information about your environment. For example, if you touch a hot stove, you will feel a sensation of pain, which will allow you to withdraw your hand before injuring it further.

The sodium-potassium pump works as follows:

  1. A carrier protein receives three sodium ions attached to it.

  2. atphydrolysis results in ADP due to the release of a phosphate group. This single phosphate group binds to the sodium-potassium pump and supplies the energy, causing a conformational change in the carrier protein.

  3. The pump or carrier protein undergoes a conformational change that allows sodium ions \((Na^+)\) to cross the membrane and exit the cell.

  4. The conformational shape of the carrier protein allows two potassium \((K^+)\) to bind to it.

  5. The phosphate group is released from the pump, causing the carrier protein to return to its original shape.

  6. This change in shape allows two \((K^+)\) of potassium to cross the membrane and enter the cell.

Primary active transport: definition and type (2)Figure 2: Sodium-potassium pump illustrated. Wikimedia Commons

Primary vs. active transport secondary

The sodium-potassium pump is an example of primary active transport because ATP binds directly to the pump.secondary active transportIt is another type of active transport. Unlike primary active transport, secondary active transport does not use ATP directly.

Instead, secondary active transport pairs or pairs transport proteins to the movement of charged ions or molecules down their concentration or electrochemical gradient to another molecule moving against their concentration or electrochemical gradient.

osodium-glucosebombais an example of secondary active transport:

  • Cells like to keep a higher concentration of sodium on the outside and a higher concentration of potassium on the inside of the cell. glucose-sodium The pump works through a transporter protein that binds glucose and two sodium ions simultaneously. This is because neither glucose nor sodium wants to go against their gradient, making sodium want to enter the cell while glucose does not.

  • The difference in energy gradient resulting from sodium wanting to enter the cell brings glucose into the cell with it. The cell needs to use the sodium-potassium pump mentioned above to remove sodium ions.

  • The sodium-glucose pump is a secondary active transport because it couples the movement of sodium down its concentration gradient with the movement of glucose, which, unlike sodium, moves against its concentration gradient. This is shown graphically in Figure 3.

Primary active transport: definition and type (3)Figure 3: Illustrated sodium-glucose pump. Wikimedia, Lady of the Hats.

Primary active transport diagram

Active transport can be classified based on which direction the molecules travel and how many there are. Thetypes of conveyorsThey are antiporters, uniporters, and symporters, as shown in Figure 4.

  • UniportadoresThey are transporters that move only one type of molecule.

  • Symportadorestransport two types of molecules in the same direction. An example of a symporter is the sodium-glucose pump.

  • Antiportadorestransport two types of molecules, but in opposite directions. An example of an antiporter is the sodium-potassium pump.

Primary active transport: definition and type (4)Figure 4: Types of Conveyors Illustrated. Wikimedia, Lupask.

oelectrochemical gradientit is a gradient consisting of a chemical and an electrical aspect, hence the name. The chemical gradient is created by the difference in the concentration of molecules inside and outside the membrane. Rather, the electrical gradient is created by the difference in charge inside and outside the membrane. Since the electrochemical gradient deals with charges, it occurs when dealing with ions or polar molecules.

Electrochemical gradients are essential in processes such asphotosynthesismiMobile phonebreathing. This is because bothbiological processesneed to generateatp. Forphotosynthesis, ATP is generated by light-dependent reactions in chloroplasts. while on cell phonebreathing, occurs in the final step called the electron transport chain (ETC). The ETC process is illustrated in Figure 5 and deals with protein complexes that create an electrochemical gradient to fuel ATP synthase and create ATP.

Other uses of electrochemical gradients arenerve impulsesthrough the sodium-potassium pump, the secretion of hormones and evenMuscle contraction. The sodium-potassium pump uses an electrochemical gradient because the ion concentration differs inside and outside the cell. Since the sodium-potassium pump works with ions, the charges are also different.

Primary active transport: definition and type (5)Figure 5: Illustrated electron transport chain. Wikimedia, Lady of the Hats.

Main types of active transport

otypes of primary active transportthey are:

  • P-type ATPase

    • They are ionic and lipid pumps found in eukaryotes and prokaryotes. Examples of this type of transporters are the sodium-potassium pump.

    • prokaryoticorganisms aresingle-celled organisms without membrane-enclosed organelles, asyou archmibacteria.

    • eukaryotessonMulticellular or unicellular organisms that have membrane-bound organelles.. its aboutanimals,plants, fungi and protists.

    • otype Prepresents the fact that these transporters can autophosphorylate.autophosphorylationrefers to the kinase that adds a phosphate group to itself. In the sodium-potassium pump, the carrier protein changes shape after being phosphorylated.

    • In humans, these ATPases controlnerve impulses, muscle relaxation and othersbiological processes.

  • F-ATPass

    • These types of transporters are found in themitochondria and chloroplasts.

    • They produce ATP by allowing protons to lower their electrochemical gradient.

  • ABC Conveyor

    • a B Csupportsatpbinding cassette. This type of transporter couples phosphates or energy groups that we passatphydrolysis with movement of molecules across membranes.

    • ABC transporters are located inprokaryotic and eukaryotic organisms.

    • ABC transporters participate insignal transduction, secretingproteins, resistance to antibiotics, etc.

    • These transporters may be involved in diseases such as cystic fibrosis. Cystic fibrosis is a genetic disease that causes many lung infections that make it difficult for those affected to breathe.

  • V-ATPase

    • V-ATPase meansVacuolar proton translocation ATPasesand is found in eukaryotic organisms.

    • These conveyors are found in manycellssuch as sperm and kidneys. V-ATPases help with coupled transport and maintain a stable pH. For example, they acidify the sperm to help it pass through the cell membrane of the egg.

Primary Active Transport - Main Findings

  • Active transportIt is a type of process that requires energy from ourcells. This energy comes in the form of ATP or adenosine phosphate.
  • Active transport requires energy because the molecules must go against their concentration gradient.
  • Active transport needs energy because the molecules want to follow its concentration gradient, not against it.
  • primary active transportit is a type of active transport that involves ATP directly. The sodium-potassium pump is one of the most famous examples of primary active transport.
  • Active transport can be classified based on which direction the molecules travel and how many there are. The types of transporters are antiporters, uniporters, and symporters.


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