Another enterprising ACP student decided to take this question one step further. Plants were grown in a closed system that allowed the student to control the amount of carbon dioxide provided to each plant. The mass of each plant was determined before and after the experiment. The results are shown below

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.