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This powerpoint presentation has been adapted from Life 4e-Lewis, Gaffin, Hoefnagels and Parker. Publishers-McGraw-Hill 1998 and Principles of Anatomy and Physiology,Tortora and Grabowski. Publishers- John Wiley & sons, Inc. 2000 AUTOTROPHY Obtaining energy from a non-living world photoautotroph chemoautotroph Two types of Autotrophs Photoautotrophs Convert CO2 and H2O to sugars utilizing light E (blue and red) Examples: plants, algae, some bacteria Chemoautotrophs Some convert CO2 and H2S to sugars utilizing chemicals(energy) such as H2S. Examples: some bacteria (hydrothermal vents) Autotrophy is the energy basis for all life on this planet. Directly keeps the autotroph alive (can make its own sugar) Indirectly keeps all of the heterotrophs alive(get eaten!) Autotrophy produces glucose Glucose will be used for: Cellular respiration Modified with minerals/other molecules to become: Nucleotides, amino acids, lipids, other carbohydrates Energy Flow Energy flows in one direction through an ecosystem. Route of energy flow is determined by an ecosystem’s trophic structure. animals that eat carnivores(tertiary consumers) animals that eat herbivores (Secondary consumers) animals that eat producers (primary consumers) photo- or chemoautotrophs Food web - several species function at more than one trophic level. I strongly suggest you view and use what is appropriate from the following link: http://photoscience.la.asu.edu/photosyn/education/learn.html PHOTOSYNTHESIS 6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O Several consequences to this evolutionary advance/mutation. Oxygen gas (O2 ) slowly built up in atmosphereAerobic respiration now a possibility UV Ozone forms (3 O2 2 O3) Life can now leave the safety of the water and colonize land Light (see page 103) Visible light makes up only a small portion of the electromagnetic spectrum. Characteristics of Visible Light: is a spectrum of colors/wavelengths ranging from violet to red consists of packets of energy called photons photons travel in waves, having a measurable wavelength () measured in nanometers (nm)10-9 A photon’s energy is inversely related to its wavelength ()... ...the shorter the ()..., the greater the energy it possesses. Which of the following photons possess the greatest amount of energy? Green photons Red photons Blue photons = 530nm = 660nm = 450nm What happens to light when it strikes an object? reflected (bounces off) transmitted (passes through) absorbed Only absorbed wavelengths of light function in photosynthesis. Photosynthetic Pigments Molecules that capture photon energy by absorbing certain wavelengths of light. Primary pigments Chlorophylls a & b - bluish green pigments found in plants, green algae & some bacteria. See page 105 Chlorophyll a is the dominant pigment in plant photosynthesis. Accessory Pigments Carotenoids - orange, yellow pigments found in plants, algae, bacteria. Anthocyanins - reds and purples Each pigment absorbs a particular range of wavelengths. See page 105 Leaf- See page 728 Chloroplasts- See page 104 Sites of photosynthesis in plants & algae. Concentrated in the palisade mesophyll cells of most plants. Chloroplast structure: See page 104 Stroma - gelatinous matrix; contains ribosomes, DNA & various enzymes. Thylakoid - flattened membranous sac; embedded with photosynthetic pigments. Chloroplast Photosynthesis. CO2 from atmosphere, H2O from soil Requires correct enzymes and pigments plus sunlight (red and blue,) ATP, NADPH to convert the reactants into the products 6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O Stomata/Stoma - pores extending through the leaf epidermis Stomata regulate gas (CO2,O2 and H2O) exchange with the environment. Usually based on their different concentration gradients, CO2 will diffuse into the leaf; H2O and O2 will diffuse out of the leaf. Photosynthesis occurs in two biochemical pathways: Light reactions - harvest photon energy to synthesize ATP & NADPH. Splits H20 Calvin cycle reactions - use ATP and NADPH from light reactions to reduce (add hydrogen/electrons) to CO2 forming carbohydrates. Overview of Photosynthesis Light Reactions require light occur in thylakoids of chloroplasts involve photosystems II & I (light harvesting systems). Photosystems contain antenna complex that captures photon energy & passes it to a reaction center. Light Reactions of Photosynthesis Light Reactions 1. Light drives both photosystems (PS). 2. Water splits, O2 formed & electron to PS II 3. excited electron enters ETC. ATP is made, similar to respiration. 4. electron replaces the one lost in PS I. 5. electron from PS I enters ETC. 6. This ETC produces NADPH Fig. 10.13 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 10.17 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings ATP Production: See page 108 Go to Light Reaction animation Go to Calvin Cycle animation Overview of Photosynthesis Carbon Reactions(Calvin cycle; C3 cycle) occurs in stroma of chloroplasts requires ATP & NADPH (from light reactions), and CO2 from atmosphere. Produces- H2O and 2 PGALs (glucose) Calvin Cycle; see pg.111 Fig. 10.18 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Photosynthesis Calvin Cycle Steps CO2 combines with the 5-carbon sugar RuBP This reaction is catalyzed by the enzyme RUBISCO The resulting unstable 6-carbon compound breaks down into 2 molecules of 3-carbon PGA The PGA molecules get energy from ATP and a H from NADPH to form PGAL. The PGAL gets rearranged and another ATP is used to recycle into RuBP. Calvin Cycle It takes 3 “turns” of the cycle to release one PGAL. It takes 2 PGALs to make a glucose. So… it takes 6 turns of the cycle to make a glucose. Each turn of the cycle is started by the entrance of one CO2. So look back at the overall equation. It takes 6CO2 to make one C6H12O6. Calvin Cycle; see pg.111 Plants that use only the Calvin cycle to fix carbon are called C3 plants. Ex. cereals, peanuts, tobacco, spinach, sugar beets, soybeans, most trees & lawn grasses. Calvin Cycle; see pg.111 Photorespiration and Special Adaptations Photorespiration: See page 118 Process that counters photosynthesis. Occurs when stomata close under hot, dry conditions: O2 levels in plant leaf increase CO2 levels in plant leaf decrease Under these conditions, rubisco attaches to O2 (rather than to CO2). Thus,less PGAL is produced (up to 50%). No known function of photorespiration Photosynthesis has produced all atmospheric O2. So when photosynthesis and Rubisco are thought to have evolved there was little to no O2 therefore photorespiration was not a problem. C3 because first stable molecule is a 3 Carbon sugar C4 and CAM Photosynthesis: See pages 119-120 Adaptations that allow certain plants to conserve water and reduce photorespiration when exposed to higher temperatures. C4 Photosynthesis C4 plants reduce photorespiration by physically separating the light reactions and Calvin cycle. Leaf anatomy of a C4 plant vs. C3 plant C4 Photosynthesis: Light reactions occur in chloroplasts of mesophyll cells. Calvin cycle occurs in chloroplasts of bundle sheath cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings CAM Photosynthesis CAM plants reduce photorespiration by acquiring CO2 at night. Therefore don’t have to open stomata and dehydrate during hot days. Night: mesophyll cells fix CO2 as malic acid malic acid is stored in vacuoles. Malic acid Day: malic acid releases CO2 which enters Calvin cycle. Fig. 10.19 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Rate of photosynthesis Rate= activity per unit of time Light intensity,water conc., temperature, conc. of oxygen and carbon dioxide All affect the rate of photosynthesis Light- see page 115 increasing light= increasing rate of photosynthesis until light saturation point, then declines. Why? CO2increasing CO2 similar curve except no decline (reaches saturation) See page 116 Temperature As temperature increases so does rate of photosynthesis, then it declines to zero. Why? See page 116 Limiting factors Light, temperature etc. all interact with each other. Factors in shortest supply have the greatest effect on the rate of photosynthesis. These are called limiting factors.. Sugar made in the chloroplasts supplies the entire plant with chemical energy and carbon skeletons to synthesize all the major organic molecules of cells. About 50% of the organic material is consumed as fuel for cellular respiration in plant mitochondria. Carbohydrate in the form of the disaccharide sucrose travels via the veins to nonphotosynthetic cells. There, it provides fuel for respiration and the raw materials for anabolic pathways including synthesis of proteins and lipids and building the Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings