8-3 The Reactions of Photosynthesis Photo Credit: ©Stone Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Parts of plant involved in photosynthesis: Stomata-On outside of plant leaf—allows for oxygen and carbon dioxide exchange….like a plant’s mouth Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Inside a Chloroplast Chloroplasts contain thylakoids—saclike photosynthetic membranes. This is where the light dependent reaction takes place. Single thylakoid Chloroplast Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Granum Chloroplast Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Photosystems Chloroplast Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Stroma – fluid portion inside chloroplast where light-independent reactions occur Stroma Chloroplast Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Electron Carriers Electron Carriers When electrons in chlorophyll absorb sunlight, the electrons gain a great deal of energy. Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Electron Carriers One carrier molecule is NADP+. Electron carriers, such as NADP+, transport electrons. NADP+ accepts and holds 2 high-energy electrons along with a hydrogen ion (H+). This converts the NADP+ into NADPH. Copyright Pearson Prentice Hall

Light-Dependent Reactions The light-dependent reactions require light. The light-dependent reactions use light energy to make two molecules needed for the next stage of photosynthesis. Using light energy and water, ATP and NADPH are made and oxygen is released. Copyright Pearson Prentice Hall

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Photosystem II captures and transfers energy (in thylakoid)

Photosystem I captures energy and produces energy-carrying molecules.

Copyright Pearson Prentice Hall SO the products of the light dependent reactions are: Oxygen ATP and NADPH (to make sugars in the Calvin Cycle) Copyright Pearson Prentice Hall

Light- dependent reactions Inside a Chloroplast H2O CO2 Light NADP+ ADP + P Light- dependent reactions Calvin Cycle Calvin cycle The process of photosynthesis includes the light-dependent reactions as well as the Calvin cycle. Chloroplast O2 Sugars Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle What is the Calvin cycle (Light Independent Reaction)? Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars. Because the Calvin cycle does not require light, these reactions are also called the light-independent reactions. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall The Calvin Cycle 1. Carbon dioxide molecules (that we have exhaled) enter the Calvin cycle The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle 2. Energy is added (ATP and NADPH from light reactions) and carbon molecules are rearranged The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle 3. Two high-energy three-carbon molecule make a sugar = C6H12O6 The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle 4. Plants use the sugars, proteins, and lipids as energy The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Light- dependent reactions Inside a Chloroplast H2O CO2 Light NADP+ ADP + P Light- dependent reactions Calvin Cycle Calvin cycle The process of photosynthesis includes the light-dependent reactions as well as the Calvin cycle. Chloroplast O2 Sugars Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall SO the product of the light independent reactions or Calvin Cycle is: Glucose = sugar for the plant = C6H12O6 because they produce their own food (the C comes from CO2) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The two sets of photosynthetic reactions work together. The light-dependent reactions trap sunlight energy in chemical form, breaking the water molecules and releasing oxygen. The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize glucose from carbon dioxide and water. The sunlight’s energy is similar to a power plant that provides energy. The removal of the water and minerals from the soil is like heavy equipment removing raw materials from the earth. The process involves green pigment chlorophyll, which is found in chloroplasts. Like a food factory, plants produce carbohydrates for use and store the starch and sugar in the plant for energy. The process generates oxygen as a byproduct. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 In plants, photosynthesis takes place inside the thylakoids. chloroplasts. photosystems. chlorophyll. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 Energy to make ATP in the chloroplast comes most directly from hydrogen ions flowing through an enzyme in the thylakoid membrane. transfer of a phosphate from ADP. electrons moving through the electron transport chain. electrons transferred directly from NADPH. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 NADPH is produced in light-dependent reactions and carries energy in the form of ATP. high-energy electrons. low-energy electrons. ADP. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 What is another name for the Calvin cycle? light-dependent reactions light-independent reactions electron transport chain photosynthesis Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 Which of the following factors does NOT directly affect photosynthesis? wind water supply temperature light intensity Copyright Pearson Prentice Hall

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