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SC BIOL 101 - Exam 3

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Chapter 10: Photosynthesis- Photosynthesis: plants, algae, cyano bacteria, sulfur bacteria, and protists are capable of this; process evolved in the cyano bacteria- Photoautotroph- photo (light energy is used to make ATP); auto (organic compounds like carbohydrates are made from inorganic compounds); sometimes called producers- they produce all the organic molecules that are used by the other organisms that cant go through photosynthesis - Chemoheterotroph- chemo (chemical energy is used to make ATP); hetero (organic compounds are obtained from others); commonly called consumers-consume the organic molecules 6CO2 + 12H2O + light= C6H12O6 + 06 6H20CO2 +2H20=CH20 +02 + H20 (simplified)(cellular respiration in reverse)o Endergonic reaction (energy in, from light)- Leaf Anatomyo Upper epidermis o Lower epidermis o Stoma- hole in the leaf; usually on the underside of the leaf; mostly in the lower epidermis; allow oxygen gas out of the leaf and CO2 to go into the leafo Cuticle- made of wax; purpose is to prevent transpiration (the evaporation of water from a plant)- they would quickly wilt o Mesophyll- central region of the cell1. Upper layer- gives most of the sunlight; composed of tightly packed vertical cells called the palisade mesophyll2. Under the palisade mesophyll is the spongy mesophyll; gets less sunlighto Veins 1. Xylem cells - xylem sap (water and minerals); type of cells that carry xylem sap up the cells2. Phloem cells (smaller on the lower side of the vein) - conduct phloem sap (rich in sucrose); cells of the root of the cells need sugar for energy cells; ex. phloem sap moves to the roots- Van Niel Standford- 1930s; studied sulfur bacteria- capable of photosynthesis; called this because they use hydrogen sulfide (2H2S) in photosynthesis instead of water; when they undergo photosynthesis you can see specs of yellow which is sulfur- Radioisotopes- radioactive oxygen called Oxygen 18- To find out where oxygen comes from in photosynthesis- experiments were done using: (radioactive isotopes) C02 + 2H20= CH2O +O2 +H20o Example of a redox reaction (involves both an oxidation-loss of electrons or hydrogen and a reduction-addition of electrons or hydrogen)o In photosynthesis- water is oxidized, and carbon dioxide is reduced o Cellular respiration=exergonic; photosynthesis= endergonic - Photosynthesis o 2 sub reactions 1. Light dependent reaction- this depends on sunlight energy to proceedH20=02o Combine ADP and a phosphate to make ATP; this process is done through chemiosmosis in the thylakoido Water is oxidized; the two hydrogens left over are given to a hydrogen truck (NADP+)- which is reduced by taking in the hydrogen and you get NADHPH+H+2. Light independent reaction (Calvin cycle)- does not require light; uses the products of the light dependent reactionCO2=CH2Oo ATP is consumed; the reduced NADPH+H+ is oxidized; the CO2 is reduced to make the carbohydrate (CH20)*****Name the two products produced in the light dependent reaction that are consumed or used in the light independent reaction: NADPH+H+ and ATPo Plants do have mitochondria- for cellular respiration - Light in photosynthesis- part of the electromagnetic spectrumo Composed of photons (have particle and wave like properties: crest to crest or trough to through is one wave link)o The energy of a photon is inversely proportion to the wave link- Ex. wave link goes down (shorter) energy goes up- Pigmentso As light meets matter, light can be:1. Reflected2. Transmitted3. Absorbed o Pigment is any substance that absorbs visible light-Blue pigment: reflects or transmits blue wavelengths-All of the other visible wavelengths of light are absorbed-Color you see absorbs everything except what you seeo Spectrophotometer- spectro=spectrum of visible light; photo=light; meter=measure; measures the spectrum of light - Engalmann (1883)- aerobic bacteria swim to the most oxygen; they swim to the purples and blues reds and oranges rather than green- Chlorophyll A- CH3 in porphynn nng- Chlorophyll B- CHO in porphytin nngo Accessory pigments- allow the plant to absorb lights that aren’t green Ranthophylls-yellow Carotenoid- orange- Deciduous trees- during fall, the trees look yellow, orange because the chlorophyll has been broken down to allow for green leaves in spring - Pigment molecules have a porphynn (suurounds a metal ion) ring Cytochromes, chlorophyll, and hemoglobin Has a hydrocarbon tail that attaches to a thylakoid  **Action spectrum of photosynthesis- measures the release of oxygen- Photo excitation of chlorophyll – uses fluorescenceo Black light is a form of uv lighto When the photon goes to the pigment it excites the pigment, the energy goes up to a higher electron shell, then falls back down to theoriginal orbital and releases energy and a pigment we can see with our own eyes (a photon with a longer wavelength)- second law of thermodynamics- Light dependent reaction of photosynthesiso Plants absorb light through a photosystemo Light harvesting complex- composed of 300 pigments and proteinso Reaction center- 2 chlorophyll, molecules, and a primary electron accepter o Photosystem- found in thrlakoid membranes Photosystem II (P680)- the wavelength of photon that the system will absorb Photosystem I (P700) Makes NADH+H+ and ATP- Linear (noncyclic) electron flow; 2 reactions ***Picture diagramo NADP+ reduced; once all reduced goes to cyclic electron flowo Electrons flow downhill releasing energy for the synthesis of ATP for chemiosmosis- Cyclic electron flowo The light independent reaction (Calvin Cycle)o Uses more ATP than NADPH+H+o The electron goes through the first ETS- Chemiosmosis- creation of a trans membrane proton gradient; the gradient isa source of potential energy for cellular work-not always for ATP synthesiso Seen in plants, animals, and bacteria; can be used in plants for secondary active transporto Review notes from last exam***- Chemiosmosis in the thylakoid- the protons are pumped from the stroma (space between grana) into the thylakoids of the grana; high concentration of protons in the thylakoid space; once the trans membrane proton gradient- they can then flow downhill and create ATPo Granum=stack of thylakoidso Photosystem along the thylakoido PH in thylakoid space=5o PH in stroma= 8o Some of the protons in the thylakoid space come from the photolysis of water (occurs in the thylakoid space) **bonuso ATP and NADP products are released into the stroma for the calvin cycle-


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