Photosynthesis conversion of light energy to chemical energy. Two classes: photoautotrophs carbon dioxide used for carbon, photoheterotrophs organic carbon sources. Found in photosynthetic membranes: plants chloroplasts, intracellular organelle, bacteria cytoplasmic membrane, internal membrane derived from cytoplasmic membrane that can become vesicles; cytoplasmic membrane but associated with specialized membrane-enclosed structures called chlorosomes; thylakoid membranes in cyanobacteria. Chlorophyll a (plants, algae, cyanobacteria: bacteriochlorphyll a (purple and green bacteria, chlorophyll a. hydrophobic segments attached to ring structure allow for pigment to associate with membrane as fatty acid chain to be inserted into membrane. different side chains give rise to different wavelengths of absorptions. ring structure that can absorb light at diff wavelengths cyclopentanone ring: bacteriophyll a. major differences are in side chains because chemical variations why they absorb at different max wavelengths. why need different chlorphylls is because by having pigments won t compete so can absorb different wavelengths of light best utilize energy.