Active Transport v/s Passive Transport

Molecules are transported across the cell membrane via active and passive transport processes. A cell membrane serves as both a structural component of the cell and a barrier to the outside world. The phospholipid bilayer maintains the cell’s delicate homeostasis, which directs the passage of chemicals in and out of the cell.

In contrast to passive transport, which does not need cellular energy, active transport uses ATP energy to push molecules against the concentration gradient. Passive transport uses a concentration channel to transfer molecules across the membrane. Molecules and ions are transported across the cell membrane by both transport mechanisms.

Active Transport

It is possible to transmit molecules (such as amino acids, glucose, ions) through a biological membrane to a location where there are already sufficient. This is known as ‘active transport’. Consequently, chemical energy is used to drive molecules across concentration gradients. Using active transport, molecules move from one part of a membrane to another where their concentrations are more significant, such as from one ion, glucose, or amino acid. Because of this, they follow the gradient of attention oppositely. Rather than using natural energy like passive transport, active transport relies on the energy stored in cells. A source of ATP is cellular respiration.

Active Transport

Active transportation methods are classified into primary active transport and secondary active transport.

• Primary active transport

In primary active transport, the molecules are transported across the membrane under the direct control of ATP as the energy source. This means that every protein that performs essential transport functions is also an ATPase, an enzyme that can hydrolyse ATP and release its energy. Na/K Pump is a well-known example of primary active transport.

The pump, which distributes sodium and potassium ions into animal cells, is one of the most important in the body’s functioning. Because it uses ATP as an energy source, the transport mechanism is characterised as the main active transportation.

• Secondary active transport

Electrochemical gradients are created by primary active transport, which stores energy that may be released when the ions descend their respective gradients. Using the energy stored in these gradients, secondary active transport can move other substances in the reverse direction of their gradients.

Secondary active transport is the movement of numerous molecules across the membrane that fuels the upward movement of a single molecule in the opposite direction. One molecule contributes to establishing the necessary gradient to allow many chemicals to flow into and out of the cell.

Importance of active transport

• Primary cellular activities, including food absorption, excretion of harmful chemicals, and signal transduction, all rely on active transport
• Higher species use secondary active transport to transfer a wide variety of substances, including ions, minerals, vitamins, and osmolytes.

Passive transport

It is the basic movement of particles and other molecular compounds inside cells along a concentration gradient without the need for external energy. Because the biochemicals are moving from an area of greater concentration to a region of lower concentration, no energy is needed for transporting the molecules in this biological process. Passive transport is used to transfer any readily soluble particles in the liquid. When this procedure is completed, the balance and equilibrium levels in a cell are maintained. Passive transport separates and transfers all waste molecules, including water and carbon dioxide, out of the cell. As a result of this diffusion, nutrients such as oxygen necessary for the cell’s activity may be delivered. Passive transport may occur by osmosis, diffusion, and assisted diffusion, to name a few methods.

Types of passive transport 

• Osmosis 

The water and other molecules or substances are carried through the selectively permeable cell membrane during osmosis. A wide range of factors influences this mode of transportation. 

• Simple diffusion

The movement of molecules or solutes through a porous membrane is referred to as ‘simple diffusion’. It is essential to keep the distance between molecules as short as possible to control the flow of non-polar molecules as efficiently as possible.

• Filtration 

Solids are removed from liquids and gases by the use of filtration. As the concentration gradient rises, this process occurs automatically. Filtration is limited by the cell membrane’s ability to allow only soluble molecules to pass through its pores.

• Facilitated diffusion

is the passive movement of ions or molecules across the cell membrane that is facilitated by the presence of particular transmembrane integral proteins. Neither cellular nor external energy is required for this process to take place.

Difference in between active and passive transport

Conclusion 

The cell’s ability to transport ions, chemicals, and even complete organisms across these membranes is essential to its survival and health. Active and passive transport are the two basic modes of cellular movement. Almost all living things rely on both modes of transportation. It may be said that active and passive transport are essential biological activities that deliver nutrients, water, oxygen, and other critical molecules to cells while also removing waste materials. Although the goals of active and passive transport are the same, the methods by which they accomplish that goal are vastly different.