They do most of the work in cells and are required for the structure, function, and regulation of the body's tissues and organs. proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains

What is the significance of the protein-lined pits? a. protein attracts other proteins needed for atp synthesis within the cell. b. protein-lined pits are able to transport one molecule at a time down the concentration gradient within the cell. c. the polarity of proteins allows other polar molecules to attach and be transported in the cell by transport channels. d. receptors within the pits allow ligands to fuse and be transported into the cell by endocytosis.