1. 4.2 Overview of Photosynthesis TEKS 4B, 9B The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9B compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter

2. 4.2 Overview of Photosynthesis TEKS 4B, 9B KEY CONCEPT The overall process of photosynthesis produces sugars that store chemical energy.

3. 4.2 Overview of Photosynthesis TEKS 4B, 9B 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.

4. 4.2 Overview of Photosynthesis TEKS 4B, 9B 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 TEKS 4B, 9B 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 TEKS 4B, 9B 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 TEKS 4B, 9B 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 TEKS 4B, 9B 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)

9. 4.2 Overview of Photosynthesis TEKS 4B, 9B The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9B compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter

10. 4.2 Overview of Photosynthesis TEKS 4B, 9B KEY CONCEPT (4.3 – Photosynthesis in Detail) Photosynthesis requires a series of chemical reactions.

11. 4.2 Overview of Photosynthesis TEKS 4B, 9B The first stage of photosynthesis captures and transfers energy. The light-dependent reactions include groups of molecules called photosystems.

12. 4.2 Overview of Photosynthesis TEKS 4B, 9B Photosystem II captures and transfers energy. –chlorophyll absorbs energy from sunlight –energized electrons enter electron transport chain –water molecules are split –oxygen is released as waste –hydrogen ions are transported across thylakoid membrane

13. 4.2 Overview of Photosynthesis TEKS 4B, 9B Photosystem I captures energy and produces energy- carrying molecules. –chlorophyll absorbs energy from sunlight –energized electrons are used to make NADPH –NADPH is transferred to light-independent reactions

14. 4.2 Overview of Photosynthesis TEKS 4B, 9B The light-dependent reactions produce ATP. –hydrogen ions flow through a channel in the thylakoid membrane –ATP synthase attached to the channel makes ATP

15. 4.2 Overview of Photosynthesis TEKS 4B, 9B The second stage of photosynthesis uses energy from the first stage to make sugars. Light-independent reactions occur in the stroma and use CO 2 molecules.

16. 4.2 Overview of Photosynthesis TEKS 4B, 9B A molecule of glucose is formed as it stores some of the energy captured from sunlight. –carbon dioxide molecules enter the Calvin cycle –energy is added and carbon molecules are rearranged –a high-energy three-carbon molecule leaves the cycle

17. 4.2 Overview of Photosynthesis TEKS 4B, 9B –two three-carbon molecules bond to form a sugar – remaining molecules stay in the cycle A molecule of glucose is formed as it stores some of the energy captured from sunlight.