1. Photosynthesis 4. References 2. Photosynthesis in Inspiration 3. Using Inspiration
Photosynthesis Photosynthesis transforms solar light energy trapped by chloroplasts into: -chemical bond energy of carbohydrates.
Autotroph vs. Heterotroph Organisms acquire organic molecules through either: 1. Autotrophic Nutrition (Auto = self; troph = feed): Producers Photoautotrophs and chemoautotrophs ex: plants, algae, some prokaryotes 2. Heterotrophic Nutrition (Heteros = other; troph = nutrition): Consumers ex: animals that eat plants or other animals, decomposers.
Chloroplasts The site where photosynthesis occurs Located in leaves Chlorophyll is located in chloroplasts Chlorophyll is the green pigment that gives photosynthetic organisms its color. Chloroplast
Chloroplasts Grana (singular granum) ThylakoidStroma Outer Membrane Inner Membrane
Chloroplasts Chlorophyll is found in the thylakoid. Converts light energy to chemical energy (PSI & PSII). Thylakoid Grana (singular granum) Stroma Outer Membrane Inner Membrane
Chloroplasts Thylakoid Grana (singular granum) Grana is stacks of thylakoids in the chloroplast Stroma Outer Membrane Inner Membrane
Chloroplasts Thylakoid Grana (singular granum) Stroma is the fluid outside the thylakoids. Uses chemical energy to convert carbon dioxide to sugar (Calvin Cycle) Stroma Outer Membrane Inner Membrane
Chloroplasts Thylakoid Grana (singular granum) Stroma Chloroplasts are surrounded by two membranes Outer Membrane Inner Membrane
Chloroplasts Thylakoid Chlorophyll is found in the thylakoid. Converts light energy to chemical energy (PSI & PSII). Grana (singular granum) Grana is stacks of thylakoids in the chloroplast Stroma Stroma is the fluid outside the thylakoids. Uses chemical energy to convert carbon dioxide to sugar (Calvin Cycle) Outer Membrane Inner Membrane Chloroplasts are surrounded by two membranes
Photosynthesis Pathway Overall equation: 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 + 6O 2 Splitting of Water: O 2 released by plants comes from the splitting of water, not from CO 2. Plants split water as a source of hydrogen and release oxygen as a by-product.
Light Reactions Overview Light (Dependent) Reactions = Convert light energy to chemical bond energy in ATP and NADPH (energy capturing rxns.) 1. Occurs in the thylakoid membrane. Two Types: 1. Cyclic (generates ATP and uses PS I) 2. Noncyclic (generates ATP and NADPH and uses PSI and PSII).
Light Independent Reactions Overview Light Independent Reactions = Calvin cycle which makes sugars (synthesis rxns). 1. Occurs in the stroma of the chloroplast. 2. Calvin Cycle (3 Parts) 1.Incorporates atmospheric CO 2 into existing organic molecules (carbon fixation) 2. CO2 Reduction 3. Regeneration of RUBP
Solar Energy Solar radiation is described in terms of its energy content and its wavelength. The electromagnetic spectrum is the range of types of solar radiation based on wavelength. Short wavelength = higher energy content and Long wavelength = lower energy content.
Solar Energy A graph of wavelength versus rate of photosynthesis is an action spectrum. Shows effectiveness of different wavelengths of visible light for driving photosynthesis. Accessory Pigments expand the range of wavelengths available for photosynthesis. - chlorophyll b: yellow-green pigment -chlorophyll a: slightly diff. absorption spectrum -carotenoids: yellow-orange hydrocarbons
Photosystems Pigments are assembled into photosystems located within the thylakoid membrane. A photosystem absorbs solar energy and generates high energy electrons. Each photosystem is composed of: -Antenna complex -Reaction-Center chlorophyll -Primary electron acceptor There are 2 types of photosystems: 1. Photosystem I P700 2. Photosystem II P680
Cyclic Electron Pathway Simplest pathway - generates ATP and no NADPH or Oxygen. It uses only PS I. It is cyclic because excited electrons that leave from the chlorophyll a at the reaction center return to the reaction center. Cyclic supplements the ATP supply required for the Calvin cycle and other metabolic pathways. Some photosynthetic bacteria use cyclic only-may have evolved early. May be utilized only when CO 2 is in limited supply.
Cyclic Electron Pathway Photons are absorbed by PS I. Reaction Center releases excited electrons to the electron acceptor. Electrons are passed to Ferredoxin. Electrons travel down Electron transport System (ETS). -as they move down ETS they pass from higher to lower energy level -energy released is stored in form of H+ gradient. -When H+ ions flow down their electrochemical gradient through ATP synthase complesxes, ATP is produced. (Chemiosmosis)
NonCyclic Electron Pathway Both PS I and PS II are used. NADPH and ATP are produced. Occurs in the thylakoid membrane. Produces Oxygen. Electrons move from water through PSI/PSII and then on to NADP+ PS II takes replacement electrons from water, which splits, releasing O 2 and H+ ions - Photolysis.
NonCyclic Electron Pathway Again in PSI, excited electrons are passed to an electron acceptor and then to ferredoxin. Ferredoxin passes the electrons to NADP+ to produce NADPH PS II absorbs light energy and boosts electrons. Electrons are passed to the primary electron acceptor and then to the ETS. Electrons lose potential energy (and produce ATP) as they move down the ETS and arrive at the PS I. Light excites electrons in PSI- these excited electrons do not return to the rxn center but are stored in NADPH.
Chemiosmosis Chemiosmosis is a coupled reaction. The thylakoid space acts as a reservoir for H+ ions; each time water is split, two H+ remain. Elecrons move carrier to carrier, giving up energy to pump H + from stroma into thylakoid space. Flow of H+ from high to low concentration across thylakoid membrane provides energy to produce ATP from ADP using the ATP synthase enzyme. In Photosynthesis this process is called photophosphorylation. ATP is produced on the outside of the thylakoid, depositing it in the stroma for use in the Calvin Cycle.
Light Independent Reactions (Dark Reactions) Light is not directly required, CO 2 is required. The Calvin Cycle uses ATP and NADPH from the light rxns to convert CO 2 to CH 2 O. (CO 2 is reduced) CO 2 reduction occurs in the stroma of a chloroplast. Calvin Cycle has 3 Parts.
Calvin Cycle: Part 1 Carbon Fixation CO 2 fixation is the attachment of CO 2 to an organic compound. RuBP is the 5 carbon molecule that combines with CO 2. Enzyme RuBP carboxylase (rubisco) speeds reaction. The product of this reaction is an unstable 6 carbon intermediate molecule
Calvin Cycle: Part 2 Reduction of CO 2 6 carbon intermediate immediately breaks down into 2 PGA molecules (3-phosphoglycerate C 3 ). Each of two PGA molecules undergoes reduction to PGAL in two steps. Light dependent reactions provide NADPH (Electrons) and ATP (energy) to reduce PGA to PGAL (G 3 P). It takes 2 PGAL to make 1 Glucose, 6 turns of the Calvin Cycle.
Calvin Cycle: Part 3 Regeneration of RuBP Every 3 turns of the Calvin Cycle, 6 PGAL are produced. 5 PGAL are used to regenerate 3 RuBP and 1 is used to build carbohydrate. It takes 2 PGAL to build 1 Glucose. PGAL is the raw material that can be used to synthesisze other carbohydrates as well To make this glucose 18 ATP and 12 NADPH are used.
Photorespiration A metabolic pathway that consumes oxygen, evolves CO2, produces no ATP and decreases photosynthesis. Occurs because active site of rubisco can accept O 2 as well as CO 2 When O 2 concentration in a leaf’s air spaces is higher than CO 2, rubisco accepts O 2 and tranfers it to RuBP. Whether photorespiration is beneficial to plants is not known. If photorespiration could be reduced in agricultural plants, crop yields and food supplies would increase. Photorespiration is fostered by hot, dry, bright days when plants don’t open stomata to reduce water loss.
Modes of Photosynthesis Sometimes PGA (a 3 carbon molecule) is not the first molecule created. C 4 plants fix CO 2 by forming a C 4 molecule prior to the involvement of the Calvin cycle. CAM plants fix CO 2 by forming a C 4 molecule at night when stomates can open without loss of water. **These alternate forms are adaptations to minimize photorespiration.
In C 3 plants, mesophyll cells contain chloroplasts arranged in parallel layers. In C 4 plants, bundle sheath cells as well as mesophyll cells contain chloroplasts. In C 4 leaves, mesophyll cells are arranged concentrically around the bundle sheath cells.
C 4 Photosynthesis C4 plants use the enzyme PEP carboxylase (PEPcase) to fix CO2 to PEP; end product is oxaloacetate (OAA-a 4 carbon molecule). OAA is then converted to malate and the malate is shuttled to bundle sheath cells. Here malate is converted to pyruvate and CO2. Pyruvate is then shuttled a back to meophyll cells where one 1 ATP is required to convert the pyruvate back into PEP. The overall effect is to move CO 2 from mesophyll cells to bundle sheath cells.
C 4 Photosynthesis The purpose of moving CO 2 to bundle sheath cells is to increase efficiency of photosynthesis. Very little oxygen reaches bundle sheath cells so when malate delivers CO 2 to them rubisco begins Calvin cycle. Because little oxygen is present here, CO 2 can be fixed without competition from O 2. Little photorespiration takes place and photosynthesis is more efficient. In hot, dry climates, net photosynthestic rate of C 4 plants is 2-3 times that of C 3 plants.
CAM Plants CAM = crassulacean acid metabolism. Exists in succulent plants adapted to very arid conditions. These plants open their stomata primarily at night and close them during the day (opposite of most plants) Conserves water during the day but prevents CO 2 from entering the leaves. When stomata are open at night, CO 2 is incorporated into a variety of organic acids.
CAM Plants During the day, light reactions supply ATP and NADPH for the Calvin Cycle. At this time, CO 2 is released from the organic acids and used to make sugars. Organic acids are stored in vacuoles until morning when the stomata close.
A Review of Photosynthesis On a global scale, photosynthesis makes about 160 billion metric tons of carbohydrate per year. No other chemical process on Earth is more productive or is as important to life. Photosynthesis transforms light energy to chemical bond energy in sugar molecules
A Review of Photosynthesis Light reactions capture solar energy and use it to produce ATP and transfer electrons from water to NADP to form NADPH. The Calvin cycle uses ATP and NADPH to fix CO 2 and produce sugar. Photorespiration can reduce photosynthetic yield in hot dry climates.
A Review of Photosynthesis Alternate methods of carbon fixation minimize photorespiration. C 4 plants spatially separate carbon fixation from the Calvin Cycle CAM plants temporarily separate carbon fixaton from the Calvin Cycle. Regardless of whether the plant uses C 3, C 4 or CAM pathway, all plants use the Calvin Cycle to produce sugar from CO 2.
Using Inspiration Opening Inspiration: 1. Go to START, then to PROGRAMS, then to Inspiration. 2. In Inspiration go to File menu. 3. Choose Save. 4. Save file as: “your last name_photosynthesis”
Using Inspiration Making your graphic organizer with Inspiration. 5. Click on the symbol with “Main Idea.” 6. Type in Photosynthesis. This is your main idea.
Using Inspiration 7. Now click on Rapid Fire located at the top menu bar.
Using Inspiration 8. Type a subtopic of Photosynthesis and then hit return. This will give you another circle. 9. Continue to type in different subtopics you would like to address. 10. Click on one of your subtopics and click on the Rapid Fire button. This will allow you to create another link off that subtopic.
Using Inspiration Adding pictures to your graphic organizer from Inspiration Library. 11. Highlight the circle you would like to change. 12. Go over to the menu bar on the left with different symbols. 13. Click on the arrow at top that will show different types of symbols. 14. Chose one and click on it. This will change your symbol.
Using Inspiration Adding pictures to your graphic organizer from the Internet. 15. Open up Internet Explorer and go to Google Images. 16.Type in key word and click search. 17. Find Image and save to desktop. 18. Don’t forget to name Image. 19. Click back on Inspriation. SAVE YOUR WORK WHEN FINISHED! 20. Go to Edit. 21. Scroll down to Insert Graphic. 22. New window will come up and click on desktop. 23. Find image and click return.