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Photosynthesis

Photosynthesis. Key Ideas. 5.1a : The energy for life comes primarily from the Sun. Photosynthesis provides a vital connection between the Sun and the energy needs of living systems.

shelley-whitney
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Photosynthesis

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  1. Photosynthesis

  2. Key Ideas • 5.1a : The energy for life comes primarily from the Sun. Photosynthesis provides a vital connection between the Sun and the energy needs of living systems. • 5.1b : Plant cells and some one-celled organisms contain chloroplasts, the site of photosynthesis. The process of photosynthesis uses solar energy to combine the inorganic molecules carbon dioxide and water into energy-rich organic compounds (e.g., glucose) and release oxygen to the environment • 5.1e: The energy from ATP is used by the organism to obtain, transform, and transport materials, and to eliminate wastes.

  3. Vocabulary • ATP (Adenosine triphosphate) – the compound in which energy released by cellular respiration is stored • Photolysis - Chemical breakdown induced by light (occurs in light-dependent reaction)

  4. Structure of a Leaf

  5. Structure of a Leaf • Cuticle – thin waxy layer that covers the leaf • Epidermis – a protective row of cells (basic structures) that forms the outer layer of leaves, green stems, and roots • Palisade mesophyll– upper portion of the leaf consisting of cylindrical cells (basic structures) that contain many chloroplasts and stand at right angles to the leaf surface • Spongy mesophyll– a leaf tissue consisting of loosely arranged, chloroplast-bearing, usually lobed cells (basic structures) • Guard cells – regulate the opening and closing of the stromates • Stromates – openings in the epidermis of leaves that allow the exchange of respiratory gases between the internal tissues of the leave and atmosphere

  6. Structure of a Chloroplast

  7. Structure of a Chloroplast

  8. Structure of a Chloroplast • The membrane of a chloroplast is a phospholipids bilayer • Stroma – in plant chloroplast, the regions between the grana • Granna– stacks of thylakoids in plant chloroplasts • Thylakoids – the photosynthetic membranes in the chloroplast which are arranged in the shape of flattened sacs • Luman – space within the thylakoid

  9. Photosynthesis • Photosynthesis – the process by which organic compounds are synthesized from inorganic carbon; ie: CO2, in the presence of light in most autotrophic organism • Consist of the Light and Dark reactions • Light-dependent reactions (Light) – in photosynthesis, a series of reactions requiring light in which water or some other compound is oxidized and ATP and NADPH are produced. Occurs in granna of chloroplast. • Light-independent reactions (Dark, Calvin) – the series of reactions in photosynthesis in which carbon fixation occurs and for which light is not required. Occurs in stroma of chloroplast.

  10. Photosynthesis Formula

  11. Light-Dependent Reaction Step 1: Light energy is received by Photosynthesis II Step 2: The light energy excites the electrons (elections jump to a higher energy state) Step 3: Electrons move down in energy states Step 4: The electrons lowering in energy states causes Hydrogen ions to be pumped across the thylakoid membrane (*Creates a concentration gradient similar to diffusion) Step 5: The high concentration of H+ in the lumen want to travel to the stroma (because of the concentration gradient)

  12. Light-Dependent Reaction Step 6: The H+ move through the ATP Synthase Step 7: The movement of the ATP Synthase causes a phosophate group to attach to ADP, creating ATP!! Light-Dependent Reaction Video: http://www.youtube.com/watch?v=BK_cjd6Evcw Additional Reactions that work together with the light-dependent reactions: • H2O  H+ + O2 (replaces the original electron that assisted with the light-dependent reaction) • NAPD + H  NADPH (where electron from H2O reaction ends up)

  13. Light-Independent Reaction • Calvin Cycle – A series of biochemical reactions that take place in the stroma of chloroplasts in photosynthetic organisms • Energy from ATP and NADPH is used to convert CO2 and H2O into organic compounds • The ATP and NADPH are products from the Light-Dependent Reaction • Key enzyme is RuBisCo, the one of the most abundant compound on Earth! • Calvin Cycle Formula: 3 CO2 + 6 NADPH + 5 H2O + 9 ATP  Glyceraldehyde-3-phosphate (G3P) + 2 H+ + 6 NADP+ + 9 ADP + 8 P

  14. Light-Independent Reaction • Calvin Cycle is divided into three phases: • Carbon Fixation – The carbon of a CO2 molecule is attached to a 5-carbon sugar (RuBP), forming an unstable 6-carbon intermediate compound, which immediately breaks down to form two 3-carbon molecules (3-phosphoglycerate : PGA). This step is catalyzed by an enzyme called RuBP. • Carbon Reduction – Each PGA molecule receives another phosphate from ATP, becoming 1,3-bisphosphoglycerate, and is then reduced by NADPH, becoming the molecule G3P (glyceraldehyde-3-phosphate : PGAL).

  15. Light-independent Reaction • RuBP Regeneration – Products must be regenerated. Of the 6 G3P molecules produced, 5 are regenerated using 3 more ATPs and a series of enzymes, producing 3 complete RuBP molecules, which are then ready to receive new CO2 molecules and continue the cycle. The sixth and final G3P molecule is a net product of the cycle. This final G3P molecule becomes the building block for the creation of large organic molecules, including glucose, fructose, sucrose and polysaccharides starch and cellulose (carbohydrate product). Calvin Cycle Video - http://www.youtube.com/watch?v=E_XQR800AgM&list=WLFDCFD6F4CBF2237F&noredirect=1

  16. Light-Independent Reaction

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