What is the primary function of channel and carrier glycoproteins in the cell membrane?

What is the primary function of channel and carrier glycoproteins in the cell membrane?

• A. Transport hydrophilic, polar, charged, or large molecules across the membrane
• B. Provide rigid structural support for the membrane
• C. Produce ATP through cellular respiration
• D. Store genetic information

Answer: (A)

The main idea here is how cells move substances that can’t easily cross the lipid bilayer. Channel and carrier glycoproteins form the specific routes that let polar, charged, or large molecules cross the membrane. Channel proteins create pores or channels that water and charged ions can pass through, usually down their concentration or electrical gradient. They don’t bind the ions permanently; they simply provide a hydrophilic passage that bypasses the oily interior of the membrane. Carrier proteins, on the other hand, bind to particular molecules (like glucose or certain amino acids) and undergo a shape change to shuttle them from one side of the membrane to the other. This can happen by facilitated diffusion (down a gradient) and, in some cases, via active transport if the carrier uses energy. The glycoprotein part mainly helps with recognition and stability on the cell surface; it doesn’t change the fundamental transport mechanism, but it can influence how well the protein performs its job or how the cell identifies itself to other cells. So, the purpose of these proteins is to move hydrophilic, polar, charged, or large molecules across the membrane, enabling uptake of nutrients and removal of wastes that wouldn’t cross on their own.

The main idea here is how cells move substances that can’t easily cross the lipid bilayer. Channel and carrier glycoproteins form the specific routes that let polar, charged, or large molecules cross the membrane.

Channel proteins create pores or channels that water and charged ions can pass through, usually down their concentration or electrical gradient. They don’t bind the ions permanently; they simply provide a hydrophilic passage that bypasses the oily interior of the membrane. Carrier proteins, on the other hand, bind to particular molecules (like glucose or certain amino acids) and undergo a shape change to shuttle them from one side of the membrane to the other. This can happen by facilitated diffusion (down a gradient) and, in some cases, via active transport if the carrier uses energy.

The glycoprotein part mainly helps with recognition and stability on the cell surface; it doesn’t change the fundamental transport mechanism, but it can influence how well the protein performs its job or how the cell identifies itself to other cells.

So, the purpose of these proteins is to move hydrophilic, polar, charged, or large molecules across the membrane, enabling uptake of nutrients and removal of wastes that wouldn’t cross on their own.