Photosynthesis

• Photosynthesis is the conversion of light to chemical energy.

• It takes place in the chloroplasts.

• Light is part of the electromagnetic spectrum.

• Radiations travel in waves and particles.

• Pigments are light-absorbing molecules. Pigments found in land plants are Chlorophyll A and Chlorophyll B.

• Each pigment has a specific absorption spectrum. ATP is an energy source.

• Pigments are light absorbers.

• NADPH are electron carriers.

• Wavelengths that are not absorbed are reflected/transmitted.

• The formula for photosynthesis is CO2 +12H20 light→ C6H12O6 + 6O2 + 6H20

• Autotrophs make their own food and heterotrophs take food from outside sources.

• Photosynthesis consists of two reactions: light reactions and carbon-fixation reactions.

• Light reactions describe light energy being used to form ATP and NADPH. Light reactions are composed of photosystems (groupings of proteins and pigment molecules).

  Photosystems I and II

• Photosystem I happens last, and Photosystems II occurs first.

• In Photosystem I, NADPH is produced.

• In Photosystem II, water molecules are split to produce oxygen (O2). The Electron Transport Chain powers the synthesis of ATP.

• Carbon-fixation reactions (Calvin Cycle) describe how ATP and NADPH used to synthesize carbohydrates.

Calvin Cycle

• The Calvin Cycle uses ATP and NADPH to synthesize carbohydrates.

• The Calvin Cycle is a cyclical pathway.

• RUBP (ribulose - 1, 5 - biphosphate) is the starting and ending compound of the cycle.

• Co2 enters plants through an opening in the leaves called “stomata.”

• The Calvin Cycle occurs in three stages: carbon fixation, reduction, and regeneration.

• In the Carbon Fixation stage, CO2 (a gas) is converted to a solid form (a carbohydrate). This is the main purpose of the Calvin Cycle.

• The Carbon Fixation stage is catalyzed by carboxylase (rubisco).

• Carbon is attached to RUBP.

• The result is two 3-carbon molecules (3PC).

• In the Reduction Phase, 3PG is reduced by NADPH with energy from the breakdown of ATP.

• This results in the formation of 2 3PG (glyceraldehyde - 3 - phosphate) molecules.

• G3P is the starting molecule for many plant cell metabolic pathways.

• In the Regeneration Cycle, there are three turns of the Calvin Cycle which generate six molecules of G3P.

• RUBP is regenerated using 5 molecules of G3P.

• The remaining G3P molecules used to synthesize carbohydrates and other necessary molecules.