Channel proteins and carrier proteins play key roles in facilitated transport across cell membranes. Only active transport involves transport proteins. The plasma membrane is essential for controlling the movement of substances in and out of the cell.
Channel proteins and carrier proteins are both involved in facilitated transport across cell membranes. Channel proteins form hydrophilic channels that allow specific substances to pass through, while carrier proteins bind with substances and aid their diffusion through the membrane.
Only active transport involves transport proteins, not just passive transport. Oxygen and carbon dioxide can indeed squeeze between the lipid molecules in the plasma membrane, and ions do not easily diffuse across the cell membrane by simple diffusion.
The plasma membrane is crucial for controlling what enters and leaves the cell, serving as a highly selective barrier that regulates the movement of substances in and out of the cell.
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