What is the Function of “pore and channel proteins”?

The plasma membrane of a typical animal cell is selectively permeable. This means certain types of chemical species may cross the barrier, but other may not, all depending on their chemical properties (such as polarity). Those that cannot cross may still be necessary to the cell (such as water). As a result, a cell has tube-like structures which are embedded in the plasma membrane, forming ';chutes'; through which these impeded ions and chemical species may traverse into the cell.





All pore or channel proteins employ a passive form of transport (which requires no expenditure on the part of the cell) called facilitated diffusion. This type of diffusion just means that a protein channel, such as these, assists the passage of an ion from it's high concentration outside the cell to it's low concentration inside the cell (or in the opposite direction, depending on concentrations).





If you want a specific example, you might google ';aquaporins';, which allow the movement of water across the plasma membrane.





To correct a minor error in a previous answer, the plasma member is permeable to gasses such as O2 and CO2. These chemicals need no assistance traversing the phospholipid bilayer of the cell membrane.What is the Function of “pore and channel proteins”?
For passive, active and facilitated diffusion (of oxygen, CO2, other ions, etc) across cell membranes





EDIT: O2, CO2 do not need transport proteins, as in passive transport, thank you Vektra, I misspoke! Facilitated and active xport do need the proteins to move from a lower concentration gradient to a higher concentration.





Think of how truck needs the motor running to get up a hill, but does not need any help to roll downhill. Analogous to the with/against concentration via transport proteins.What is the Function of “pore and channel proteins”?
They span through the width of the cell membrane to allow for transport of particles into and out of the cell by active or passive transport.