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Photosynthesis: Trapping the Sun’s Energy

Photosynthesis: Trapping the Sun’s Energy. Section 9.2. PG. 225. When it comes to writing titles, bigger is better. Leaf Structure. Stomata – Tiny openings/pores found mostly on the under-side - Play a role in gas exchange Guard Cells – Control the opening/closing of stomata

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Photosynthesis: Trapping the Sun’s Energy

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  1. Photosynthesis: Trapping the Sun’s Energy Section 9.2 PG. 225 When it comes to writing titles, bigger is better.

  2. Leaf Structure Stomata – Tiny openings/pores found mostly on the under-side - Play a role in gas exchange Guard Cells – Control the opening/closing of stomata Spongy Mesophyll – Photosynthetic tissue of the leaf Lower Epidermis – The outer layer of the bottom. Contains stomata and provides protection.

  3. Make a quick sketch of the left including the “kidney-shaped” guard cells Surface views of a stomata Water moves in Water moves out Epidermal cells Nucleus Guard cells (Balloons) Chloroplasts Stoma closes Stoma opens Guard cell relaxed – Stoma closed Guard cell swollen – Stoma open Side view of a stoma PG. 619

  4. Leaf Structure Phloem (“phood”)– Made up of tubular cells that transport sugars Xylem (Wxyz)– Made of tubular cells that transport water and minerals Vascular bundle – Contains xylem, phloem, and supporting/protective tissues Palisade mesophyll – Vertical cells below the upper epidermis that contain more chlorophyll than the spongy layer Upper epidermis – Contains much less stomata than the lower epidermis. Provides protection. Covered by a waxy cuticle. Cuticle – Waxy coating that prevents water loss.

  5. Photosynthesis is the process that uses the sun’s energy to make simple sugars - LIGHT ENERGY  CHEMICAL ENERGY - Simple sugars are converted into complex carbohydrates, such as starches, which store energy Photosynthesis occurs in two stages: - Light-dependent (Light) reactions - Light-independent (Dark) reactions There is an equation you have to memorize……..”Awww man!” It is the equation for photosynthesis. TRAPPING ENERGY FROM SUNLIGHT

  6. Photosynthesis Equation What is the ONE thing that we keep talking about that plants use that is missing from this equation? Sunlight Energy!!! CO HO  OCHO 6CO + 6H O  6O + C H O 2 2 2 6 12 6 6 Carbon Dioxides + 6 Waters Yields 6 Oxygens + 1 Glucose

  7. Chloroplasts and pigments Recall that chloroplasts are the organelles where photosynthesis occurs Chloroplasts contain thylakoid disks Inside these disks is where the light reactions occur Thylakoids also contain light-absorbing pigments that gather sunlight. A granum is a stack of thylakoids (10-100) per chloroplast Chlorophyll is the most common pigment

  8. Chloroplast structure

  9. Wavelengths of light What color is sunlight?

  10. Wavelengths of light Which color of the spectra gets absorbed the least by chlorophyll?

  11. More pigments Carotenoids are accessory pigments in all photosynthetic organisms • Carotene reflects orange • Xanthophyll reflects yellow • Anthocyanin is a pigment that appears after the breakdown of chlorophyll. It reflects red to blue

  12. LIGHT-DEPENDENT REACTIONS

  13. Sunlight strikes chlorophyll in the thylakoid as a photon Light energy is transferred to electrons (eˉ ) The electron transport chain (ETC) is the series of proteins embedded in the thylakoid membrane passing electrons The eˉ lose energy that is used for ADP  ATP or to pump hydrogen ions (H+ ) to the center of the thylakoid The eˉ are re-energized and passed down a 2nd ETC eˉ are transferred to the stroma of the chloroplast using NADP+ NADP+ can become NADPH to be used in the dark reactions Overview

  14. 1. Light (photon) strikes photosystem II - energy is absorbed and passed along until it reaches P680 chlorophyll 2. Excited eˉ is passed to primary electron acceptor

  15. 3. Photolysis (splitting water) takes the electrons from water replaces the P680 electrons that were passed to the primary electron acceptor. ( O2 gas released as a waste product)

  16. 3. Photolysis (splitting water) takes the electrons from water replaces the P680 electrons that were passed to the primary electron acceptor. ( O2 gas released as a waste product) 4. The electrons are passed to photosystem I via the ETC and also used to pump protons across the thylakoid membrane into the lumen 5. The stored energy in the proton gradient is used to produce ATP which is used later in the Calvin-Benson Cycle 6. P700 chlorophyll then uses light to excite the electron to its second primary acceptor 7. The electron is sent down another ETC and used to reduce NADP+ to NADPH 8. The NADPH is used later in theCalvin-Benson Cycle

  17. e– ATP e– e– NADPH e– e– e– Mill makes ATP Photon e– Photon Photosystem I Photosystem II

  18. ANIMATIONS & TUTORIALS http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm http://www.fw.vt.edu/dendro/forestbiology/photosynthesis.swf http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html# http://www.wiley.com/legacy/college/boyer/0470003790/animations/electron_transport/electron_transport.htm http://wps.prenhall.com/esm_krogh_biology_3/0,8750,1135943-,00.html http://science.nhmccd.edu/biol/bio1int.htm#photo http://www.biology.arizona.edu/biochemistry/problem_sets/photosynthesis_1/photosynthesis_1.html http://www.biology.arizona.edu/biochemistry/problem_sets/photosynthesis_2/photosynthesis_2.html http://www.johnkyrk.com/

  19. LIGHT-INDEPENDENT REACTIONS

  20. Overview Also known as the Dark reactions or Calvin Cycle, is located in the stroma A series of reactions that use Carbon Dioxide and NADPH from the light reactions NADPH   NADP+ ATP   ADP CO2   C6H12O6 (Glucose) Carbon fixation – Carbon is “fixed” into a 6-Carbon sugar - similar to soybeans that fix Nitrogen 6-Carbon sugar is broken down into two 3-Carbon sugars After more reactions, one 3-Carbon sugar is available for making sugars, carbohydrates, and starches.

  21. Use the diagram below to refer to the notes that follow.

  22. 1. A Carbon molecule enters the cycle and joins an existing 5-Carbon molecule – Ribulose Bisphosphate (RuBP) by RuBisCO (enzyme) 2. The 6-Carbon molecule breaks into two 3-Carbon molecules of 3-Phosphoglycerate (3PGA) 3. ATP  ADP powers PGA kinase to change six 3PGA molecules into 6 Diphosphoglycerates (DPGA) 4. NADPH  NADP+ further powers the system so GAP dehydrogenase can make 6 molecules of Glyceraldehyde Phosphate (PGAL) a.k.a Glyceraldehyde 3-phosphate (G3P) 5. One PGAL molecule is used to make glucose and other high-energy sugars 6. By ATP  ADP the remaining 5 PGALs are used to reformthe RuBP used in step one so the cycle can repeat

  23. SUMMARY Calvin Cycle uses CO2, NADPH, & ATP to make Glucose, NADP+, & ADP ANIMATIONS http://fig.cox.miami.edu/~cmallery/150/phts/calvin.mov http://www.treca.org/staff/voss/Pages/calvincycle2.html Sucrose is the sugar found at home that is made up of glucose (left) and fructose (right).

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