Water (H20)Edit


A molecule of water

Molar Mass: 18g/mol

Location: Everywhere in the cell

Purpose: Becomes oxidized by chlorophyll a (P680)

Other information:

  • Oxidizing potential is -1.23, the redox potential of chlorophyll a is 1.3V. This is the reason that chlorophyll a (P680) can oxidize water.



Pheophytin, is essentially a Chlorophyll a molecule with out the Mg+ ion

Molar Mass: 871.2 g/mol

IUPAC Name:4beta,21beta]]-14-ethyl-21-(methoxycarbonyl)-4,8,13,18-tetramethyl-20-oxo-9-vinylphorbine-3-propionate

Location: Found in the oxygen evolving complex in photosystem II

Purpose: Pheophytin is involved in electron transfer from the chlorophyll a molecules (P680) in PS II to plastoquinone.



A molecule of Chlorophyll a

Molar Mass: 893.49 g/Mol

IUPC Name: [(2E,7R,11R)-3,7,11,15-tetramethylhexadec-2-en-1-yl (22R,17S,18S)-7-ethyl-21,22,17,18-tetrahydro-22-(methoxycarbonyl)-3,8,13,17-tetramethyl-21-oxo-12-ethenylcyclopenta[a't]porphyrin-18-propanoato(2−)]magnesium

Location: Chlorophyll a is found in both the LHC II proteins and in the oxygen evolving complex. It can also be found in photosytem I and the light-harvesting complex associated with PS I

Purpose: In land plants, chlorophyll serves two roles. Its first function is ressonance energy transfer in both the light-harvesting complex and the oxygen evolving complex proteins. The other function is to oxidize water.

Other information:

  • There are two main types of chlorophyll in land plants: Chlorophyll a and phlorophyll b. Both of these molecules can be identified by their slightly different absorbtion spectra.
  • In land plants, the concentration of chlorophyll in a leaf is an excellent indicator of how healthy a plant is. Chlorophyll production is sensitive to many differnt enviromental factors. Additionally, the ratio of chlorophyll a to b is another indicator of how well a plant is doing.



Plastoquinone as it is before it it reduced by Pheophytin

Molar Mass: 749.20 g/mol

IUPAC Name: 2,3-dimethyl-5-[(2E,6E,10E,14E,18E,22E,26E,30E)-3,7,11,15,19,23,27,31,35-nonamethylhexatriaconta-2,6,10,14,18,22,26,30,34-nonaen-1-yl]cyclohexa-2,5-diene-1,4-dione

Location: Plastoquinone is found in the oxygen evolving complex protein.

Purpose: Sequesters two electons from pheophytin and then shuttles them off to the next protein in photosynthesis, Cytochrome b6f.


  1. Rogelio: Photosystem II: Introduction
  2. Rogelio: Photosystem II: Biological function
  3. Rogelio: Photosystem II: Biosynthesis
  4. Rogelio: Photosystem II: Gene sequence
  5. Rogelio: Photosystem II: Amino acid sequence and composition
  6. Rogelio: Photosystem II: Secondary and tertiary structure
  7. Rogelio: Photosystem II: Domains and structural motifs
  8. Rogelio: Photosystem II: Interactions with macromolecules and small molecules
  9. Rogelio: Photosystem II: Molecular biodiversity and evolution
  10. Rogelio: Photosystem II: Literature overview
  11. Rogelio: Photosystem II: Useful online resources