• Autotrophs - synthesize their own food using energy from non-organic source. The vast majority of autotrophs (such as plants) use energy from the sun via photosynthesis.
• Heterotrophs - need high energy organic compounds that are ultimately derived from autotrophs.

The most common photosynthesis reaction is a follows:

6CO₂ + 12H₂O + light ------> C₆H₁₂O₆ + 6H₂O + 6O₂

You often see water (H₂O) on both sides of this reaction to emphasize that the oxygen (6O₂) on the right side comes from the 12 H₂O's on the left side. The Hydrogens from those waters combine with the 6CO₂'s to make 6 molecules of water and one molecule of glucose (C₆H₁₂O₆). The glucose can then be used in a variety of cellular processes. You can simplify this equation by removing the extra H₂O's from both sides to give:

6CO₂ + 6H₂O + light ------> C₆H₁₂O₆ + 6O₂

Pigments are molecules that are especially good at absorbing light. Visible light is a very small portion of the electromagnetic spectrum but a portion both we (in our sight) and plants (in photosynthesis) interact strongly with. Photosynthetic pigments absorb certain frequencies of light and transfer that energy to the photosystem reaction center to start the process of capturing that light energy in high-energy organic compounds (like sugar). The major photosynthetic pigments are the chloorphylls (especially chlorophyll a and chlorophyll b). There are also accessory pigments

Paper Chromatography

Gas Chromatography

From PSTCC's Official Practical Review

• Know the overall formula for photosynthesis.
• What is chromatography?
• What is meant by the visible light spectrum?
• Be able to identify pigments on a strip of chromatography paper based on their location and appearance.
• Explain how chromatography separates plant pigments.
• How are Rf values calculated?
• What is spectrophotmetry?
• Be able to graph, and interpret graphs showing the absorption spectrum of the photosynthetic pigments.