Chloroplast An organelles that specializes in photosynthesis in plants and many protists. Plant chloroplast have two outer membranes , and are filled with a semifluid matrix call the stroma. Stroma contains the chloroplast’s DNA, some ribosomes, and an inner, much-folded thylakoid membrane. The folds of a thylakoid membrane typically forms stacks of disks that are connected by channels. The space inside all of the disks and channels is a single, continuous compartments. Many thylakoids together make a granum.

Chlorophyll A molecule in chloroplasts that absorbs some of the energy in visible light. Chlorophyll α and β absorbs mostly red and blue wavelengths (λ) of visible light. Neither type absorbs much green light. As a result, the green color of plants comes from the reflection of the light’s wavelengths by the chlorophyll.

Only light between 380 – 750 nm drive photosynthesis. Electromagnetic Spectrum

Photosynthesis A process that captures energy from sunlight to make sugar that store chemical energy. Photosynthesis uses energy captured from the sunlight to change carbon dioxide and water into oxygen and sugars (glucose). Sunlight is absorbed during the light-dependent reactions and sugars are made during the light-independent reactions.

Photosynthesis Photosynthesis is actually a series of many reactions that occur in two stages. Light-dependent Light-independent

6CO2 + 6H2O + Light C6H12O6 + 6O2

Light-dependent Reaction First stage; capture energy from sunlight. These reactions take place in the thylakoid membrane. Water and sunlight are need for this process. Chlorophyll absorbs energy from sunlight. The energy is transferred along the membrane. Water molecules are broken down. Oxygen molecules are released. Energy carried along the membrane is transferred to molecules that carry energy, ATP and NADPH.

Light-Dependent Reactions The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Photosynthesis begins when pigments in photosystem II absorb light, increasing their energy level. Photosystem II The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall These high-energy electrons are passed on to the electron transport chain. Photosystem II Electron carriers High-energy electron Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Enzymes on the thylakoid membrane break water molecules into: Photosystem II 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. Electron carriers High-energy electron Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall hydrogen ions oxygen atoms energized electrons Photosystem II + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. Electron carriers High-energy electron Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The energized electrons from water replace the high-energy electrons that chlorophyll lost to the electron transport chain. Photosystem II + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. High-energy electron Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall As plants remove electrons from water, oxygen is left behind and is released into the air. Photosystem II + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts. High-energy electron Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane. Photosystem II + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. High-energy electron Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Energy from the electrons is used to transport H+ ions from the stroma into the inner thylakoid space. Photosystem II + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall High-energy electrons move through the electron transport chain from photosystem II to photosystem I. Photosystem II + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. Photosystem I Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Pigments in photosystem I use energy from light to re-energize the electrons. + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. Photosystem I Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall NADP+ then picks up these high-energy electrons, along with H+ ions, and becomes NADPH. + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall As electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane. + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Soon, the inside of the membrane fills up with positively charged hydrogen ions, which makes the outside of the membrane negatively charged. + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The difference in charges across the membrane provides the energy to make ATP + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall H+ ions cannot cross the membrane directly. ATP synthase + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The cell membrane contains a protein called ATP synthase that allows H+ ions to pass through it ATP synthase + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall As H+ ions pass through ATP synthase, the protein rotates. ATP synthase + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP. ATP synthase + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. ADP 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Because of this system, light-dependent electron transport produces not only high-energy electrons but ATP as well. ATP synthase + O2 2H2O The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. ADP 2 NADP+ 2 2 NADPH Copyright Pearson Prentice Hall

Light-independent Reaction/Calvin Cycle Second stage; uses energy created in the light-dependent reaction to make sugars. This reaction takes place in the stroma of the chloroplast. Carbon Dioxide is needed during this stage of photosynthesis. CO2 is added to a cycle of chemical reactions to build larger molecules. Energy from the light-dependent reaction is used. A carbohydrate (C6H12O6) molecule is made, which stores energy that was captured from sunlight.

Copyright Pearson Prentice Hall Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules. CO2 Enters the Cycle The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The result is twelve 3-carbon molecules, which are then converted into higher-energy forms. The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The energy for this conversion comes from ATP and high-energy electrons from NADPH. Energy Input 12 12 ADP 12 NADPH The Calvin cycle uses ATP and NADPH to produce high-energy sugars. 12 NADP+ Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Two of twelve 3-carbon molecules are removed from the cycle. Energy Input 12 12 ADP 12 NADPH The Calvin cycle uses ATP and NADPH to produce high-energy sugars. 12 NADP+ Copyright Pearson Prentice Hall

The molecules are used to produce sugars, lipids, amino acids and other compounds. 12 12 ADP 12 NADPH The Calvin cycle uses ATP and NADPH to produce high-energy sugars. 12 NADP+ 6-Carbon sugar produced Sugars and other compounds Copyright Pearson Prentice Hall

The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle. 12 12 ADP 6 ADP 12 NADPH 6 The Calvin cycle uses ATP and NADPH to produce high-energy sugars. 12 NADP+ 5-Carbon Molecules Regenerated Sugars and other compounds Copyright Pearson Prentice Hall

The two sets of photosynthetic reactions work together. The light-dependent reactions trap sunlight energy in chemical form. The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and the hydrogen from water.