Final answer:
Carrier proteins in the plasma membrane function to facilitate molecular transport across the membrane, which is essential for maintaining cellular internal conditions. They bind specific molecules, change shape, and selectively transport these molecules into or out of the cell.
Step-by-step explanation:
Function of Plasma Membrane Proteins
The plasma membrane performs various essential functions in cellular activity. One of the major roles of proteins in the plasma membrane is to facilitate molecular transport through the membrane. This is particularly important for molecules that cannot easily pass through the hydrophobic lipid bilayer.
Carrier proteins are one type of membrane protein that aid in the transport of specific molecules or particles. They bind to a substance, change shape and move the substance from outside to the inside of the cell, or in the opposite direction against a concentration gradient. This selectivity of carrier proteins is key to maintaining the plasma membrane's selective permeability.
Without these proteins, certain essential molecules and ions would not be able to effectively move in and out of cells, thus affecting the cell's ability to function properly. Given that the proteins are specific to certain substances and have a limited number that can be saturated, they enable a finely tuned regulation of substance concentration inside the cell. These transport systems are crucial in maintaining the necessary internal conditions despite external environmental changes.