Photosynthesis: 5.2B In detail

1. Photosynthesis: 5.2B In detail

2. Photosynthesis: Stage 1 • Stage 1: Absorption of Light Energy • When the sun shines on you, your body is bombarded by many different kinds of radiation from the sun. • Different types of radiation, such as light or heat, have different wavelengths. • Light is a form of radiation, energy in the form of waves that travel through space. • Sunlightcontains all the wavelengths of visible light; the colors of the rainbow.

3. Stage 1: Pigments • How does a human eye or leaf absorb light? They both posses pigments. • Pigments are light absorbing substances that absorb only certain wavelengths and reflect all others. • Chlorophyll, the primary pigment involved in photosynthesis, absorbs mostly blue and red light and reflects green and yellow. • This reflection of green and yellow gives plants their green appearance.

4. Pigments Plants contain two types of chlorophyll • Chlorophyll A and Chlorophyll B • Plants also contain carotenoids. Carotenoids are pigments that produce yellow and orange fall leaf colors, as well as the colors of many fruits and vegetables and flowers. • Carotenoids absorb different wavelengths of light than chlorophyll so having both pigments allows plants to absorb more light energy during photosynthesis.

5. Stage 1: Production of Oxygen • Pigments involved in plant photosynthesis are located in the chloroplasts of leaf cells. • Clusters of pigments are embedded in the membranes of disk-shaped structures called thylakoids • When sunlightstrikes a thylakoid in a cell, light energyis transferred to electrons in chlorophyll.

6. Stage 1: Production of Oxygen • These excited electrons jump from chlorophyll molecules to other nearby molecules in the thylakoid membrane. • The excited electrons that leave chlorophyll molecules must be replaced by other electrons. • Plants get these replacement electrons from water molecules.

7. Stage 1: Production of Oxygen • When water molecules are split, chlorophyll molecules take the electrons from hydrogen atoms, leaving hydrogen ions (H+). • The remaining oxygen atoms from the disassembled water molecules combine to form oxygen (02)

8. Stage 2: Conversion of Light Energy • Excited electrons that leave chlorophyll molecules are used to produce new molecules, including ATP. • First an excited electron jumps to a nearby molecule in the thylakoid membrane. • Than the electron is passed, like a bucket brigade, through a series of molecules along the thylakoid membrane called an electron transfer chain

9. Electron Transfer Chains • How are electron transport chains used to make molecules that temporarily store energy in the cell? • A series of transport chains controls this process. • The first transport chain consists of a protein that acts as a membrane pump. • Excited electrons lose some of their energy as they pass through this system. • The energy lost by the electrons is used to pump hydrogen ions into the thylakoid.

10. Electron Transfer Chains • As the process continues, hydrogen ions become more concentrated inside the thylakoid • As a result, hydrogen ions tend to diffuse back out of the thylakoid through specialized carrier proteins.

11. Electron Transfer Chains • As hydrogen ions pass through the channel portion of the protein, the protein catalyzes a reaction in which a phosphate group is added to a molecule of ADP, making ATP. • As a result, the movement of hydrogen ions across the thylakoid membrane through these proteins provides the energy needed to make ATP, which is used to power the third stage of photosynthesis.

12. Electron Transfer Chains • While one electron transport chain provides the energy used to make ATP, another second chain provides the energy used to make NADPH. • NADPHis an electron carrier that provides high-energy electrons needed to make carbon-hydrogen bonds in the third stage of photosynthesis.

13. Stage Three: Storage of Energy • In the third stage of photosynthesis, carbon atoms from the carbon dioxide in the atmosphere are used to make organic compounds (sucrose) in which chemical energy isstored. • Carbon dioxide fixationis the name given to this transfer of carbon dioxide to organic compounds. • The reactions that “fix” carbon dioxide are sometimes called “dark reactions”or “light independent reactions”

14. Calvin Cycle • The most common method of carbon dioxide fixation is the Calvin Cycle • The Calvin Cycle is a series of enzyme-assisted chemical reactions that produces a three-carbon sugar

15. Steps of the Calvin Cycle Step 1: • In carbon dioxide-fixation, each molecule of carbon dioxide is added to a five-carbon compound by an enzyme. • This results in a six carbon molecule. 1

16. Calvin Cycle: Step 2 Step 2: • The resulting six carbon compound splits into two three-carbon compounds • Phosphate groups from ATP and electrons from NADPH are added to the three-carbon compounds forming three-carbon sugars 2

17. Calvin Cycle: Step 3 Step 3: • One of the resulting three-carbon sugars is used to make • organic compounds, including starch and sucrose, • in which energy is stored for later use by the organisms. 3

18. Calvin Cycle: Step 4 Step 4: • The other three-carbon sugars are used to regenerate the initial five-carbon compound, thereby completing the cycle. • The final product is the creation of sugars in the form of glucose that provides the food energy for the plant’s survival. 4

19. Calvin Cycle: Creation of Sugars • The reactions in the Calvin Cycle are cyclic.They recycle the five-carbon compound needed to begin the cycle again. • A total of three carbon dioxide molecules must enter the Calvin cycle to produce each three-carbon sugar that will be used to make other compounds. • The energy used in the Calvin Cycle is supplied by ATP and NADPHmade during the second stage of photosynthesis.

20. Factors that Affect Photosynthesis • Photosynthesis is directly affected by various environmental factors. • In general, the rate of photosynthesis increases as light intensity increases until all pigments are being used. • At this point of saturation, the Calvin Cycle is working as fast as it can. • In general, the more sunlight available, the faster photosynthesis will happen!

21. Factors that Affect Photosynthesis • Photosynthesis, however, is most efficient at certain temperature ranges. • When temperature ranges fall outside the range that the enzymes function, the enzymes will become inactive and the process slows down or stops.

22. Follow the Steps of Photosynthesis: • sunlightstrikes a thylakoid in a cell, light energyis transferred to electrons in chlorophyll. • Water (H20) is split in the process releasing hydrogen ions and oxygen (O2) as a byproduct of the process. • Exited electron moves through “electron transfer chains” producing hydrogen ions. • Hydrogen ions enter cell, combine with ADP to create ATP. Also combine with NADP + H to create NADPH. • In Calvin Cycle, • CO2 + ATP + NADPH 5 carbon sugars (glucose) • Part of the glucose goes back into the cycle making it happen again so more glucose is created.

23. Section Review • Key Concepts. . . . • Photosynthesis has three stages • First energy is captured from sunlight • Two, energy is temporarily stored in ATP and NADPH • Third, organic compounds are made using ATP, NADPH, and Carbon Dioxide • Pigments absorb light energy during photosynthesis. • Electrons excited by light, travel through electron transport chains, in which ATP and NADPH are produced. • Through carbon dioxide fixation, by the Calvin Cycle, carbon dioxide in the atmosphere is used to make organic compounds (glucose), which store energy and provide the plant with food. • Photosynthesis is directly affected by environmental factors such as the • intensity of light, • availability of water, • the concentration of carbon dioxide, • and temperature range.

24. Computer Lab Assignment • In the Computer Lab: • Research photosynthesis on the internet • Watch the video at the following link on photosynthesis • Photosynthesis video • Photosynthesis video 2 • Create a one page written report in Word (or a 5 page mini-presentation in PowerPoint) following the steps of photosynthesis in their order