Final answer:
The cell membrane's primary function is to regulate the movement of solutes across it, being selectively permeable to small, nonpolar molecules and requiring transport proteins for larger or hydrophilic substances. Transport methods include simple diffusion, osmosis, and facilitated diffusion, the latter involving transmembrane proteins that assist larger or charged particles to move across the membrane without energy expenditure.
Step-by-step explanation:
One of the most important functions of the cell membrane is to regulate the movement of dissolved solute from the liquid on one side of the membrane to the liquid on the other. The cell membrane is selectively permeable, meaning it allows some substances to pass through while restricting others. This function is critical for maintaining homeostasis within the cell by controlling the internal environment.
The cell membrane is composed of a phospholipid bilayer, which is selectively permeable to small, nonpolar substances like oxygen and carbon dioxide. Larger or hydrophilic substances, such as water, glucose, amino acids, and ions, require transport proteins to help them cross the membrane. These proteins include channel proteins and transporter proteins like the sodium/potassium pump.
There are several mechanisms for transport across the cell membrane including:
- Simple diffusion - movement of small, hydrophobic molecules directly through the lipid bilayer.
- Osmosis - the diffusion of water molecules across the membrane.
- Facilitated diffusion - utilizes transport proteins to move hydrophilic substances and ions across the membrane without expending energy.
Each of these transport mechanisms plays a vital role in ensuring the cell's survival by regulating the flow of material into and out of the cell.