Photosynthesis:Absorption and Conversion

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Photosynthesis Absorption and Conversion of Energy

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Autotrophs An autotroph is an organism that can make its own food through. auto: self -troph: organism

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All organisms must break down carbohydrates, or other complex molecules, to form energy molecules, such as Adenosine Triphosphate (ATP).]

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ATP. Computer artwork of a molecule of adenosine triphosphate (ATP), which is a carrier of metabolic energy in the cell. Energy is stored in the chemical bonds and is released when the molecule is broken down. Illustration by PROF. K.SEDDON & DR. T.EVANS, QUEEN'S UNIVERSITY BELFAST The chemical formula of ATP is C 10 H 16 N 5 O 16 P 3 .

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Photograph by Stanley Mikles, September 2006, West of Emily Minnesota 1. Light is the purest form of energy and the prime source of energy of all life. a. provides energy for photosynthesis b. visible spectrum: array of colors formed when white light passes through a prism c. photons: unit of light energy d. color of an object seen by the eye is the color of light reflected by the object

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Photo by Dr Tim Evans 2. Chlorophyll Chlorophyll a: C 55 H 72 O 5 N 4 Mg Chlorophyll b: C 55 H 70 O 6 N 4 Mg

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Photo by Dr Tim Evans 2. Chlorophyll a. found in chloroplasts (in Eukaryotes) 1) plants ( C 55 H 72 O 5 N 4 Mg ) (Chlorophyll a) 2) some algae ( C 35 H 30 O 5 N 4 Mg (Chlorophyll c1) b. found in cytoplasm of prokaryotes c. necessary for photosynthesis to begin d. absorbs energy from all but the green portion of the visible spectrum e. several types of chlorophylls are active

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Chlorophyll a Found in all photosynthetic organisms C 55 H 72 O 5 N 4 Mg Chlorophyll b Plants C 55 H 70 O 6 N 4 Mg Chlorophyll c1 Some Algae C 35 H 30 O 5 N 4 Mg Chlorophyll c2 Some Algae C 35 H 28 O 5 N 4 Mg Chlorophyll d Cyanobacteria C 54 H 70 O 6 N 4 Mg

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b. carotene: orange pigments 3. Other pigments are involved a. xanthophylls: yellow pigments that absorb light energy in other parts of the spectrum and pass the energy on to chlorophyll

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f. chlorophyll: acts as a light (energy) trap during photosynthesis 1) when a photon strikes a chlorophyll molecule and is absorbed, the photon’s energy is transferred to an electron of the chlorophyll molecule 2) The energized electrons are stretched like rubber bands – but they cannot remain for long in this “excited state” a) raised to a higher energy level b) as electron returns to original level, it releases absorbed energy c) this energy is used in chemical reactions in the cell

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4. Chloroplast: plastid that stores chlorophyll (plastid: sack) BIOPHOTO ASSOCIATES

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Granum A stack of thylakoid membranes Thylakoid membrane Sack containing chlorophyll

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a. photosynthesis begins in “thylakoid membrane” of a “granum” b. stroma: dense fluid that fills the space between the grana and the chloroplastic membrane (also known as photo centers) PROF. KENNETH R. MILLER

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DR KARI LOUNATMAA Pisum sativum

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Granum

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Thylakoid membrane

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DR JEREMY BURGESS Pisum sativum Starch Grain

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DR JEREMY BURGESS Coleus blumei Starch Grain

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The Origin of Chloroplasts? Chloroplast Dividing

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Algae: Spirogyra Chloroplasts Chlorophyll c1

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Some Facts About Light 3) Mass of photon: @ less than mass of electron (9.0 x 10 -31 kg) Trapping of light energy and formation of materials needed in the next phase . A. light energy: photon : packet of light energy 1) c = 3.0 x 10 8 meters/second =186,000 mile/sec 2) E=mc 2

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Photosynthesis occurs in two phases. I. Light-Dependent Reactions : Trapping of light energy and formation of materials needed in the next phase .

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A. chlorophyll molecules in thylakoid membranes struck by photon

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B. Chlorophyll molecular bonds broken releasing energy (excited electrons) 1. Excited electrons move down electron transport chain. a. Embedded In the thylakoid membrane are a series of proteins whose electrons are very excitable. b. The excited electrons move from protein to protein in the thylakoid. c. At each protein, the electrons lose energy d. Some of the energy lost at each step is used to combine ADP and loose phosphate ions (P) to form ATP.

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NADH NAD + H + H + H + Electron Transport Chain Thylakoid Membrane ADP + P ATP Energy is from light striking chlorophyll Hydrogen from hydrophotolysis

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Light strikes chlorophyll in thylakoid membrane Excited electron jumps to next protein Energy is released Excited electron jumps to next protein

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e. Some of the energy lost at each step is used to split water molecules through a process called hydrophotolysis . 1) H + used in next phase 2) O + O O 2 This is the source of 98% of all the free, molecular oxygen in our atmosphere. Photo by DR JEREMY BURGESS Open Stomata First Photo System H 2 O H 2 + O 2H 2 O 2H 2 + 2O O 2 diffuses out of chloroplast into cytoplasm, diffuses out of cell and into intercellular space, diffuses to stomata, and is released by transpiration into the atmosphere.

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Lower epidermis of Geranium Leaf at 40x

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Stomata in Lower epidermis of Geranium Leaf at 400x Guard Cells Stomata Opening

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Lower epidermis of Geranium Leaf at 400x

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Stomata of Lower Epidermis of Geranium Leaf at 1000x

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Joseph Priestley (1733-1804 GEORGE BERNARD 1. British chemist. 2. Best known as the discoverer of oxygen. 3. Carried out research into the composition and nature of air. 4. First person to recognize that respiration in animals produces carbon dioxide whereas in plants it produces oxygen. 5. In his work on carbon dioxide, Priestley invented soda water; the precursor to all carbonated drinks. 6. He was a Unitarian Calvinist minister and a supporter of the French Revolution. Eventually his political views led to his house being burnt down and him fleeing England.

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f. “second photo system” and a “second electron transport chain” g. The “lost” energy at each protein jump is used to bond NADP - to H + . h. The energy is also used to transport the NADPH into the stroma by active transport . i. NADPH is used in the “light independent reactions”.

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II. Light Independent Reactions (aka: Dark Reactions, Dark Phase, Calvin Cycle) A. Energy stored in ATP used as energy source in Light Independent Reactions. (ADP + P ATP) B. CO 2 from atmosphere supplies carbon and oxygen atoms for glucose. (C 6 H 12 O 6 ) C. NADPH from light dependent reactions used a source of hydrogen used in making glucose D. Occurs in the stroma of the chloroplast

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D. Light Independent Reactions (Calvin Cycle) 1. Carbon Fixation One molecule of CO 2 is added to one molecule of RuBP (ribulose biphosphate), forming one unstable six carbon molecule.

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D. Light Independent Reactions (Calvin Cycle) 2. Formation of two 3 – carbon molecules. The unstable 6 carbon molecule immediately breaks down into 2, 3—carbon molecules of PGA.

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D. Light Independent Reactions (Calvin Cycle) c. Energy from ATP and NADPH forms the two PGA into 2 PGAL (phosphoglyceraldehyde). 3. Conversion of PGA to PGAL a. One molecule of ATP broken into ADP and P b. One NADPH broken into NAPD - and H +

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Melvin Calvin LAWRENCE, BERKELEY NATIONAL LABORATORY Photographed in 1961. 1941

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1. 3. Reactions in the Calvin Cycle a. Co 2 and a 5-carbon molecule ( RuBP ) combine to form a 6-carbon molecule : ( unstable intermediate ) “carbon fixation” b. H 2 O + 6 carbon molecule  2, 3-carbon molecules (2PGA) c. 1 ATP molecule broken--energy used to: d. NADPH + H +  NADP + H 2 e. Result = 2, 3-carbon sugars ( 2PGAL ) PGAL: Phosphoglyceraldehyde f. 1PGAL  6 carbon sugar ( glucose: C 6 H 12 O 6 ) g. 1PGAL returns to beginning of cycle h. ATP split: ATP  ADP + P + energy i. Yields return of 5-carbon molecule RuBP from 1PGAL (back to start)

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III. Synthesis without sunlight: Chemosynthesis 1. methane producers 2. Chemoautotrophs 3. digestive tracts 4. break down of sewage 5. break down of oil spills (bacteria)

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Stephen Hales (1677-1761) English chemist and physiologist. His book Vegetable Staticks (1727) describes 124 experiments on gases, which he made in several ways and collected using a pneumatic trough. He measured growth rates in plants, and showed that light is needed, and that water loss (by transpiration) is through the leaves and that this causes an upward flow of sap. Later experimented on blood pressure in animals and investigated the vascular system in general. Other studies involved the Preservation of foods, water purification, the ventilation of buildings and ships, and also the best way to support pie crusts.

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Melvin Calvin LAWRENCE, BERKELEY NATIONAL LABORATORY Photographed in 1961. 1941

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Melvin Calvin . (born 1911), Portraits show Melvin Calvin, an American biochemist, in his photosynthesis research laboratory. He began to study photosynthesis in 1946 when sensitive analytical methods became available. He identified in single-celled Chlorella algae a cycle of photosynthetic reactions using radioactive forms of carbon dioxide. Photosynthesis is the process by which green plants convert light, water & carbon dioxide into food and oxygen. The discovery of this reductive pentose phosphate or Calvin cycle, which occurs in all photosynthesizing organisms, won Calvin the 1961 Nobel Chemistry Prize.