Question

question ① protein channels within the plasma membrane ________. select all that apply permit water and ion movement at all times open or close to regulate ion passage can act as an enzyme transport only lipids

Explanation:

1. Analyze "permit water and ion movement at all times": Some protein channels (like aquaporins for water, leak channels for ions) are always open, allowing constant movement. So this applies.
2. Analyze "open or close to regulate ion passage": Gated protein channels (e.g., voltage - gated, ligand - gated) open/close to control ion flow, so this applies.
3. Analyze "can act as an enzyme": Some membrane proteins (including channel - like proteins in some cases) have enzymatic activity, so this can apply.
4. Analyze "transport only lipids": Protein channels are for transporting ions, water, or other polar molecules, not lipids (lipids move through the lipid bilayer). So this does not apply.

Answer:

• $\square$ permit water and ion movement at all times (checked)
• $\square$ open or close to regulate ion passage (checked)
• $\square$ can act as an enzyme (checked)
• $\square$ transport only lipids (un - checked)