Final answer:
The cell membrane regulates a cell's internal environment, maintaining homeostasis by selectively allowing substances in and out. It ensures optimal levels of nutrients and ions are present while expelling wastes, adapting to changes in the external environment.
Step-by-step explanation:
Controlling Cell Contents and Maintaining Homeostasis
The cell membrane is integral to a cell's ability to maintain homeostasis. It is semipermeable or selectively permeable, meaning it controls the passage of substances into and out of the cell. Homeostasis refers to the maintenance of a stable internal environment within the cell or an organism, vital for normal cell function. For instance, balancing the concentrations of ions like Na+, K+, and other organic molecules, is essential. Furthermore, this balance contributes to health at the organismal level, influencing risks for conditions such as high blood pressure and heart disease.
The cell membrane actively regulates the internal conditions, ensuring that essential nutrients are absorbed while wastes, including CO2, are expelled. This regulation allows cells to function properly despite changes in the external environment, like temperature fluctuations. Homeostasis is a dynamic equilibrium, not a static state, and requires continuous adjustments to maintain the conditions within the optimal range for cell vitality.