Final answer:
The term a)'integral' is the correct choice to complete the sentence, referring to proteins that span the membrane and help transport substances in and out of the cell.
Step-by-step explanation:
The correct term to complete the sentence about the cell membrane is 'The lipid cell membrane and its a)integral proteins help the cell to move nutrients and other molecules in and out of the cell.'
Integral proteins span the hydrophobic interior of the lipid bilayer, providing a path for certain substances to cross the membrane. They are distinct from peripheral proteins, which are found on the membrane's surface and may be involved in signaling or substratum adhesion. Integral proteins include channel proteins and pumps, which directly facilitate the transport of ions, nutrients, and other substances into and out of the cell.