Question

select all that apply
select the functions of proteins in the plasma membrane.

• proteins span the entire membrane and create tunnels through which certain substances enter and leave the cell.
• proteins at the inner surface of the plasma membrane anchor the plasma membrane to the cell’s internal support structure, giving the cell its shape
• when found on the outer surface of the plasma membrane, proteins called receptors transmit signals to the inside of the cell
• proteins help to prevent the fatty-acid tails of the phospholipid bilayer from sticking together.
• proteins that stick out from the plasma membrane define the cell’s characteristics and help cells identify chemical signals

Explanation:

1. First option: Integral membrane proteins (like channel proteins) span the membrane, forming tunnels (channels) for substances to move in/out. Correct.
2. Second option: Inner - surface proteins (e.g., cytoskeletal - associated proteins) anchor the membrane to the cell's internal structure (cytoskeleton), maintaining cell shape. Correct.
3. Third option: Receptor proteins on the outer surface bind to extracellular signals (like hormones) and transmit the signal into the cell. Correct.
4. Fourth option: Cholesterol (not proteins) helps prevent fatty - acid tails from sticking together. So this is incorrect.
5. Fifth option: Glycoproteins (proteins sticking out) act as cell - surface markers for cell identification and chemical signal recognition. Correct.

Answer:

• Proteins span the entire membrane and create tunnels through which certain substances enter and leave the cell.
• Proteins at the inner surface of the plasma membrane anchor the plasma membrane to the cell’s internal support structure, giving the cell its shape.
• When found on the outer surface of the plasma membrane, proteins called receptors transmit signals to the inside of the cell.
• Proteins that stick out from the plasma membrane define the cell’s characteristics and help cells identify chemical signals.