How do cell membranes help organisms maintain homeostasis?
Cell membranes regulate the movement of materials into or out of cells.
By controlling what enters and leaves the cell, the membrane can regulate the processes of waste removal and bringing in needed supplies.
Carbon dioxide is a waste molecule cells produce when they carry out the process of cellular respiration. Carbon dioxide builds up in the cell (high concentration) so it diffuses out of the cell into the blood stream (lower concentration). The blood carries carbon dioxide to the lungs where it can enter the air sacs of the lungs and be exhaled.
Other materials are needed by the cells. Cells need glucose to provide energy. Glucose can move from the blood stream (where it is more concentrated) into cells (where there is a lower glucose concentration) by travelling through channel proteins in the membrane. This process is called facilitated diffusion. It works like this...
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