Photosynthesis light phase and dark phase balanced

1. LIGHT DEPENDENT REACTION

Photolysis: H2O --- H+  + O2  + e-

Light is absorbed by the pigments found in the chloroplasts: clorophyll a, b and carotenoids

The light absorbed is used to break down the water molecule (photolysis). Water is broken down into O2, protons and electrons. The H+ and e- are needed for next reaction, but O2 is released into atmosphere.

Light absorbed results in formation of ATP

2. LIGHT INDEPENDENT REACTION

NADPH --- is a donor/aceptor of H+ and e-. It carries the H+ and e- obtained in the first reaction to be used in the second phase of photosyntesis. ATP produced in the first reaction is used here to produce carbon copunds

H2O ---- O2 + e- + H+  + ATP

CHANGES TO EARTH DUE TO PHOTOSYNTHESIS

Oceans - oceans initially had high levels of dissolved iron (released from the crust by underwater volcanic events)

Atmosphere- for the first 2 billion years after the earth was formed, its atmosphere was anoxic (oxygen free)

Rock dposition - The reaction between dissolved iron and oxygen gas created oceanic deposits called bonded iron formations (BIFs)

Biological life - free oxygen is toxic to obligate anaerobes and increase in O2 levels many have wiped out many of these species

LIMITING FACTORS ON RATE OF PHOTOSYNTHESIS

- temperature

- light intensity

- CO2 concentration