By Stephanie Chandler
Updated Mar 24, 2022
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A membrane surrounds every living cell, safeguarding its interior from external influences. Temperature is a critical determinant of membrane behavior, influencing what substances can cross the barrier and how membrane‑associated molecules perform their functions. Extremes of temperature—either too hot or too cold—can damage or even kill cells by disrupting membrane integrity.
Cell membranes are bilayers composed of two opposing layers of phospholipids. Each phospholipid has a hydrophilic head and a hydrophobic tail, enabling the membrane to remain fluid yet semi‑permeable. This design allows gases like oxygen and carbon dioxide, as well as small lipophilic molecules, to diffuse across, while excluding larger or potentially harmful entities.
Embedded within this fluid matrix are two classes of proteins: peripheral proteins, which attach to the surface, and integral proteins, which span the bilayer. Their mobility within the membrane allows cells to respond to changing conditions and maintain homeostasis. As cells grow, the membrane expands proportionally, preserving its fluidity to accommodate increased surface area.
Cells thrive at their physiological temperature—98.6 °F (37 °C) for mammals. When temperature rises, such as during a fever, the fatty‑acid tails of phospholipids become less ordered, increasing membrane fluidity. While this can enhance the movement of proteins and molecules, it also elevates permeability, potentially allowing deleterious substances to enter. Prolonged exposure to high heat can denature integral and peripheral proteins, compromising cellular function.
Conversely, cooling reduces the kinetic energy of phospholipid tails, making the bilayer more rigid. Reduced fluidity hampers the transport of essential nutrients like oxygen and glucose, slowing metabolic processes and cell growth. In extreme cold, intracellular water can crystallize, puncturing the membrane and leading to cell death.
