The boundaries of a cell are determined by the presence of a lipid bilayer known as the cell membrane. This nonpolar structural feature enables the cell to have specific characteristics within the intracellular compartment relative to its extracellular environment. In order to maintain a constant environment, cells need to regulate their internal and external environment. This can be accomplished through structures such as channels, which allow for specific substrates to travel from an area of high concentration to an area of low concentration. These channels are essential in the regulation of the cellular environment.
The Nobel Prize for 2003 in Chemistry was awarded to two scientists who are exploring channels in the cell membrane. The Nobel Prize was awarded to Dr. Peter Agre, who examines the movement of water through the membrane channel, aquaporin, and to Dr. Roderick MacKinnon, who explores the movement of ions across the membrane, specifically the movement of potassium through the K+ channel.
The lipid bilayer of cell membranes is impermeable to water. Movement of water needs to be regulated in order to maintain the internal pressure of the cell. The presence of water channels, such as aquaporin, enables the cell to regulate the water content of cells to prevent swelling or shrinking. This feature is especially important in the filtration system of the kidneys.
Within the nervous system, cells communicate to one another through action potentials. These signals are dependent on the movement of ions across the cell membrane. The movement of potassium ions is essential for these communications. The structure of the potassium channel is specific to potassium ions through the presence of the selectivity filter. This filter is composed of amino acids positioned in such a way that the carbonyl oxygens can coordinate the potassium ion as it moves through the membrane.
Students can explore the different ways that substrates can be moved through the lipid bilayer with the models in this collection. The two channels serve similar purposes, but their structures are unique.