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Chapter 8.3 The Reaction of Photosynthesis. The Chloroplast Site of photosynthesis.

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Presentation on theme: "Chapter 8.3 The Reaction of Photosynthesis. The Chloroplast Site of photosynthesis."— Presentation transcript:

1 Chapter 8.3 The Reaction of Photosynthesis

2 The Chloroplast Site of photosynthesis

3 The Chloroplast thylakoidInner membrane thylakoid –Highly folded so there is an increased surface area for absorption of sunlight granaStacks of thylakoids grana photosystemsClusters of chlorophyll and other pigments photosystems stromaLiquid filling of chloroplast stroma

4 Electron Carriers A carrier molecule is a compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule Main electron carrier of photosynthesis NADP+ Turns into NADPH when it is carrying electrons

5 Photosystems There are two different groupings of photosystems in photosynthesis Light dependent reactions Happens on the thylakoid membrane Has 2 photosystems (II and I) Light independent reactions Happens in the stroma Calvin cycleAlso known as the Calvin cycle

6 Chloroplast Light O2O2 Sugars CO 2 Light- Dependent Reactions Calvin Cycle NADPH ATP ADP + P NADP + Chloroplast Section 8-3 Figure 8-7 Photosynthesis: An Overview

7 Photosynthesis includes of take place in takes place in uses to produce use Light- dependent reactions Calvin cycle Thylakoid membranes StromaNADPH ATP Energy from sunlight ATPNADPHO2O2 Chloroplasts High-energy sugars Section 8-3 Concept Map

8 Light Dependent Reactions Part of photosynthesis that requires light Use light energy to produce ATP and NADPH, as well as oxygen

9 Light Dependent Reactions Pigments of photosystem II absorb light Energy is absorbed by electrons High energy electrons are transferred to NADP+ (electron carrier molecule) –These electrons are replaced by electrons produced by the breakdown of water Water is broken down into 2 electrons, 2 H+ ions, and 1 oxygen atom –Oxygen is released –Hydrogen is broken apart and released inside the thylakoid

10 Light Dependent Reactions The high energy electrons are passed through the electron transport chain between photosystem II to photosystem I –The energy from the electrons is used to transport H+ ions from the stroma into the inner thylakoid space

11 Light Dependent Reactions Light hits the electrons that are now in photosystem I to excite them again –These high energy electrons are picked up by NADP+ –The NADP+ also picks up the H+ ions to make NADPH

12 Light Dependent Reactions As the electrons move onto the NADP+, more H+ ions are pumped across the membrane –Eventually, the outside of the thylakoid becomes negatively charged and the inside becomes positively charged Difference in charge provides the energy to make ATP

13 Light Dependent Reactions Thylakoid membrane contains an enzyme called ATP synthase H+ ions pass through it to synthesize ATP –This energy will be used to make energy- containing carbohydrates

14 Video 3 Click the image to play the video segment. Video 3 Light-Dependent Reactions, Part 1

15 Video 4 Click the image to play the video segment. Video 4 Light-Dependent Reactions, Part 2

16 Hydrogen Ion Movement Photosystem II Inner Thylakoid Space Thylakoid Membrane Stroma ATP synthase Electron Transport Chain Photosystem IATP Formation Chloroplast Section 8-3 Figure 8-10 Light-Dependent Reactions Light Dependent Reactions


18 Light Independent Reactions Also known as the Calvin cycle Plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time Does not require light

19 Light Independent Reactions Six carbon dioxide molecules enter the cycle from the atmosphere to produce 1 6-carbon sugar As the cycle continues, 12 3-carbon molecules are created –These 3-carbon molecules obtain energy from ATP and NADPH to become high energy 3- carbon molecules.

20 Light Independent Reactions Two of the 12 3-carbon molecules are removed from the cycle –Used to make sugars, lipids, amino acids, and other materials needed for plant metabolism and growth –Rest of the 3-carbon molecules combine to make 6 5-carbon molecules

21 Factors that Affect Photosynthesis Presence of waterPresence of water Lack of water slows down photosynthesis –Plants also have evolved ways to help prevent water loss (waxy covering on leaves) TemperatureTemperature Enzymes function best at 0-35 degrees Celsius Intensity of LightIntensity of Light Increasing light intensity increases the rate of photosynthesis –There is a certain amount of light intensity where the amount of photosynthesis within a plant does not change

22 Video 5 Click the image to play the video segment. Video 5 Calvin Cycle

23 ChloropIast CO 2 Enters the Cycle Energy Input 5-Carbon Molecules Regenerated Sugars and other compounds 6-Carbon Sugar Produced Section 8-3 Figure 8-11 Calvin Cycle


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