Which of the following pigments is present in all algae?
Chlorophyll itself is actually not a single molecule but a family of related molecules, designated chlorophyll a, b, c, and d. Chlorophyll a is the molecule found in all plant cells and therefore its concentration is what is reported during chlorophyll analysis. Chlorophyll d is found only in marine red algae, but chlorophylls b and c are common in fresh water algae. The molecular structure of chlorophylls a and b consists of a ring-like structure called a porphyrin and a long organic phytol "tail." In the center of the porphyrin ring is a magnesium molecule. Chlorophyll c lacks the phytol chain. The relative concentrations within the cell of these chlorophylls varies with the species of algae, but chlorophyll a is dominant in all the eukaryotic algae and the prokaryotic blue-green algae (Cyanobacteria).