Chapter 9 Energy in a Cell Section 2 Photosynthesis

Photosynthesis Photosynthesis is the the process by which plants convert the sun’s energy into simple sugars.

Photosynthesis The general equation for photosynthesis is: 6CO2 + 6H20 + sunlight C6H1206 + 6O2

Photosynthesis Photosynthesis happens in two phases: Light-dependent reactions Light-independent reactions

Where Does Photosynthesis Take Place? Photosynthesis takes place in the chloroplasts. Light-dependent reactions in thylakoid. Light-independent reactions in stroma.

Pigments The thylakoid membranes contain pigments to trap the sun’s energy. Chlorophyll is the most common pigment – reflects green light making plants look green.

Pigments When plants stop producing chlorophyll in the fall, the other pigments can be seen.

Light-Dependent Reaction Light hits the chlorophyll, exciting the electrons and creating energy. Splits Water molecules (photolysis) Forms ATP molecules Used in light-independent reactions Hydrogen atoms help form NADPH molecules Releases oxygen

Light Independent Reactions The second phase of photosynthesis is called the Calvin Cycle or dark reaction. The Calvin Cycle does not require light. In the Calvin Cycle is a series of steps that change CO2 into glucose or sugar.

Calvin Cycle Carbon Dioxide is absorbed by the plant. The Calvin cycle uses the NADPH and ATP (from Light-dep rxn) to run the cycle that converts the gas into glucose (C6H12 O6)

Photosynthesis

Photosynthesis

Another way to make food Chemosynthesis—making organic molecules as food from inorganic compounds (nitrogen or sulfur). Only specific species of bacteria are this type of producer. Examples– are nitrogen-fixing bacteria in soil (legumes) or bacteria on sulfur vents at the bottom of the ocean.