Question

proteins characterized as channels and carriers are ______.
attachment proteins
transport proteins
motility proteins

Explanation:

Transport proteins facilitate the movement of substances across cell membranes. Channels and carriers are types of transport proteins: channels form pores for ion or small molecule passage, carriers bind to substances and change shape to transport them. Attachment proteins (e.g., for cell - cell or cell - matrix adhesion) and motility proteins (involved in cell movement or organelle motion) do not have the channel/carrier function.

Answer:

B. transport proteins