Difference between Carrier and Channel Proteins

To keep cells active and alive, it is necessary to transport different substances across the cell membrane – the outermost, protective layer of a cell. These water soluble and insoluble substances are primarily transported across the plasma membrane of the cell through special proteins, known as the membrane transport proteins.

There are two types of membrane transport proteins called channel proteins and carrier proteins. The basic function of both these proteins is to let polar molecules like ions, amino acids, sugar, metabolites and nucleotides pass across the plasma membrane.

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    Though the function of both these proteins is same, there are a number of differences between the two which clearly make them different from one another. Solute particles diffuse through the pores of channel proteins, whereas carrier proteins bind solutes on one side of the plasma membrane and release them on the other side. Moreover, channel proteins have a very fast transport rate as compared to carrier proteins.

    Channel proteins contain a pore which facilitates the transport of substances across the plasma membrane. Carrier proteins lack this pore and this is the reason why transportation rate of the latter is quite slow as compared to the former. Channel proteins also lack alternate solute-bound conformations, but they are present in carrier proteins. Moreover, carrier proteins can carry out both active and passive transportation of solutes, whereas channel proteins bring about passive transport only.
    Both carrier proteins and channels proteins also differ in their chemical composition - whilst the former are glycoproteins, the latter are lipoproteins. Furthermore, carrier proteins are formed on free ribosomes in the cytoplasm, whereas channel proteins are formed on ribosomes bound to the endoplasmic reticulum.

    Carrier proteins transport both water soluble and insoluble molecules across the cell membrane, whereas channel proteins pass only water soluble substances. Channel proteins cannot transport solutes (ions and molecules) against the concentration gradient, while carrier proteins can. While transporting molecules or ions, channel proteins do not move across the plasma membrane, whereas carrier proteins do move across the membrane.

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    Carrier proteins

    Carrier proteins are the intrinsic membrane proteins that are involved in the movement of ions or molecules across a biological membrane, like a cell membrane or a plasma membrane.

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    Channel proteins

    Channel proteins are also integral membrane proteins found in the phospholipid bilayer membranes in the bodies of living organisms, and facilitate solute transportation across a biological membrane. These proteins are ion selective and allow only specific ions and molecules to pass through.

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