1. 4.2 Overview of Photosynthesis KEY CONCEPT The overall process of photosynthesis produces sugars that store chemical energy.

2. 4.2 Overview of Photosynthesis Photosynthetic organisms are producers. Producers make their own source of chemical energy. Plants use photosynthesis and are producers. Photosynthesis captures energy from sunlight to make sugars.

3. 4.2 Overview of Photosynthesis A few types of organisms do not need sunlight and photosynthesis as a source of energy. Some organisms live in places that never get sunlight. In chemosynthesis, chemical energy is used to build carbon-based molecules. –similar to photosynthesis –uses chemical energy instead of light energy

4. 4.2 Overview of Photosynthesis Chlorophyll is a molecule that absorbs light energy. chloroplast leaf cell leaf In plants, chlorophyll is found in organelles called chloroplasts.

5. 4.2 Overview of Photosynthesis Photosynthesis in plants occurs in chloroplasts. Photosynthesis takes place in two parts of chloroplasts. –grana (thylakoids) –stroma chloroplast stroma grana (thylakoids)

6. 4.2 Overview of Photosynthesis The light-dependent reactions capture energy from sunlight. –take place in thylakoids –water and sunlight are needed –chlorophyll absorbs energy –energy is transferred along thylakoid membrane then to light-independent reactions –oxygen is released

7. 4.2 Overview of Photosynthesis The light-independent reactions make sugars. –take place in stroma –needs carbon dioxide from atmosphere –use energy to build a sugar in a cycle of chemical reactions

8. 4.2 Overview of Photosynthesis The equation for the overall process is: 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 granum (stack of thylakoids) thylakoid sunlight 1 six-carbon sugar 6H 2 O 6CO 2 6O 2 chloroplast 1 2 43 energy stroma (fluid outside the thylakoids)