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 autotrophs (producers). Autotroph means “self feeding”. They make stored chemical energy. Plants are autotrophs. They use the process of photosynthesis to make energy. Photosynthesis captures energy from sunlight to make sugars. (starch)

3. 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.

4. 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) There are two part to the photosynthesis process. –Light dependent reaction –Light independent reaction

5. 4.2 Overview of Photosynthesis The light-dependent reactions capture energy from sunlight. –take place in thylakoids –water and sunlight are needed –chlorophyll absorbs solar energy –ADP is converted into ATP –energy is transferred along thylakoid membrane then to light-independent reactions –oxygen is released

6. 4.2 Overview of Photosynthesis The light-independent reactions make sugars. –take place in stroma –needs carbon dioxide from atmosphere –ATP is converted to ADP, releasing energy –Energy is used to build a sugar in a cycle of chemical reactions called the Calvin Cycle

7. 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) Light Dependent Reaction Light Independent Reaction