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Presentation on theme: "PHOTOSYNTHESIS."— Presentation transcript:


2 KEY CONCEPT Photosynthesis is a series of chemical reactions that transform light energy into chemical energy stored in food.

3 Chemical Equation of Photosynthesis
Sunlight Energy 6CO2 + 6H2O C6H12O6 + 6O2 Carbon dioxide + Water Glucose + Oxygen REACTANTS PRODUCTS Carbon dioxide Glucose (sugar) Water Oxygen chlorophyll Sunlight Energy chlorophyll


5 CO2 diffuses into leaf cells through stomata pores

6 Water is absorbed by osmosis through the roots

7 In plants, Photosynthesis occurs in chloroplasts.
leaf cell leaf Chloroplasts are green colored organelles that contain the green pigmented molecule chlorophyll Chloroplast = Organelle Chlorophyll= Molecule

8 Structure of the Chloroplast Organelle
1.) Thylakoids- coin shaped compartments surrounded by a membrane 2.) Grana – Stacks of coin shaped thylakoids 3.) Chlorophyll – light absorbing green molecule in thylakoid membrane 4.) Stroma – Fluid filled space between grana chloroplast stroma grana (thylakoids)

9 There are Two Main Stages of Photosynthesis
1. Light-Dependent Reactions – Require Light Energy 2. Light-Independent Reactions – Do Not Require Light Energy

10 Light-Dependent Reactions - capture energy from sunlight.
*Light energy is needed *Water is needed *Occur in the chlorophyll filled thylakoid membrane *Produce molecules that provide E to Light Independent Rxns. (ATP and NADPH – High Energy Molecules) *Waste byproduct is Oxygen

11 Basic Steps of the Light Dependent Reactions
1. Light energy “excites” the electrons in the chlorophyll molecule. 2. “Excited”, high energy electrons are passed from one protein molecule to another along the electron transport chain in the thylakoid membrane and are picked up by two molecules: NADP to form NADPH High E molecules needed to ADP to form ATP power the Light Independent Rxns 3. Enzymes split the water molecule: H2O 2H+ + 2e- + O- * The 2e- replace the electrons the chlorophyll molecule lost * Oxygen gas is released

12 Light-Independent Reactions (Calvin Cycle)
Do NOT require light energy – can happen in the dark Requires ATP and NADPH as energy source Occurs in the stroma CO2 needed. CO2 enters through the leaf stomata by diffusion Glucose molecules made

13 Basic Steps of the Light Independent Reactions (Calvin Cycle)
1. CO2 molecules diffuse across the stroma. 2. CO2 is rearranged using H+ and Energy from ATP and NADPH to make glucose. Carbon gets ”fixed” into organic compounds – Carbohydrates, Lipids, Proteins

14 Light Dependent Reactions – Capture Light Energy
Light Independent Reactions - Make Sugars

15 The equation for the overall process is:
6CO2 + 6H2O  C6H12O6 + 6O2 C6H12O6 granum (stack of thylakoids) thylakoid sunlight 1 six-carbon sugar 6H2O 6CO2 6O2 chloroplast 1 2 4 3 energy stroma (fluid outside the thylakoids)

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