Question

question 2 protein channels within the plasma membrane ______. select all that apply transport only lipids can act as an enzyme open or close to regulate ion passage permit water and ion movement at all times

Explanation:

1. Analyze "transport only lipids": Protein channels in the plasma membrane are for transporting ions, polar molecules, etc., not lipids (lipids can move through the lipid bilayer). So this is incorrect.
2. Analyze "can act as an enzyme": Some membrane proteins (including channel - like associated proteins or other integral membrane proteins) can have enzymatic activity. So this is a correct option.
3. Analyze "open or close to regulate ion passage": Many ion channels in the plasma membrane are gated, meaning they can open or close to control the passage of ions. This is a key function of protein channels (especially ion channels). So this is correct.
4. Analyze "permit water and ion movement at all times": Most protein channels (like gated ion channels or aquaporins which can be regulated) do not allow movement at all times; they are regulated (open/closed) based on cellular signals or conditions. So this is incorrect.

Answer:

B. can act as an enzyme, C. open or close to regulate ion passage