Phytochromes are pigment molecules that act as photoreceptors and are found in plants. Enzymes are biocatalysts that cause a change in the rate of a chemical reaction. Chloroplasts are cell organelles that are present mostly in plant cells and help capture sunlight and in photosynthesis. Proteins are biomolecules formed of long amino acid chains that are necessary for a cell to function. Proteins are involved in carrying out nearly all the functions of a cell.