What mechanism describes the process of specific molecules crossing membranes with the help of protein channels?

What mechanism describes the process of specific molecules crossing membranes with the help of protein channels?

• A. Simple Diffusion
• B. Facilitated Diffusion
• C. Active Transport
• D. Pinocytosis

Answer: (B)

The correct choice describes facilitated diffusion, which is a key mechanism in cell biology. This process allows molecules to cross the cell membrane with the assistance of specific protein channels or carriers. Unlike simple diffusion, where molecules move directly through the lipid bilayer without any assistance, facilitated diffusion involves these specialized proteins that help transport larger or polar molecules that cannot easily penetrate the hydrophobic core of the membrane. Facilitated diffusion is a type of passive transport, meaning it occurs without the expenditure of energy, allowing substances to move across the membrane down their concentration gradient—from an area of higher concentration to an area of lower concentration. This is vital for the uptake of essential nutrients like glucose and the movement of ions, which are polar and therefore cannot diffuse freely through the lipid layer. This process is distinct from active transport, which requires energy to move molecules against their concentration gradient, whereas facilitated diffusion relies on the inherent concentration gradient. Pinocytosis, on the other hand, involves the engulfing of liquids or small particles into the cell, a form of endocytosis, rather than the specific transport of molecules through a protein channel.

The correct choice describes facilitated diffusion, which is a key mechanism in cell biology. This process allows molecules to cross the cell membrane with the assistance of specific protein channels or carriers. Unlike simple diffusion, where molecules move directly through the lipid bilayer without any assistance, facilitated diffusion involves these specialized proteins that help transport larger or polar molecules that cannot easily penetrate the hydrophobic core of the membrane.

Facilitated diffusion is a type of passive transport, meaning it occurs without the expenditure of energy, allowing substances to move across the membrane down their concentration gradient—from an area of higher concentration to an area of lower concentration. This is vital for the uptake of essential nutrients like glucose and the movement of ions, which are polar and therefore cannot diffuse freely through the lipid layer.

This process is distinct from active transport, which requires energy to move molecules against their concentration gradient, whereas facilitated diffusion relies on the inherent concentration gradient. Pinocytosis, on the other hand, involves the engulfing of liquids or small particles into the cell, a form of endocytosis, rather than the specific transport of molecules through a protein channel.