The main chemical difference between human blood and chlorophyll is the type of metal ion in their respective molecules. Blood contains iron in the form of heme groups in hemoglobin, while chlorophyll contains magnesium in the center of its porphyrin ring structure. This difference in metal ions is what gives blood its red color and chlorophyll its green color.
And here is a little reminder of what Chlorophyll do:
Chlorophyll’s job in a plant is to absorb light—usually sunlight. The energy absorbed from light is transferred to two kinds of energy-storing molecules. Through photosynthesis, the plant uses the stored energy to convert carbon dioxide (absorbed from the air) and water into glucose, a type of sugar. Plants use glucose together with nutrients taken from the soil to make new leaves and other plant parts. The process of photosynthesis produces oxygen, which is released by the plant into the air.
https://education.nationalgeographic.org/resource/chlorophyll/
