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11/21/17 Lecture Notes – Chapter 9Plants, algae, and (some) bacteria can undergo photosynthesisCO2 is being used, O2 is being releasedSome factories plant trees around their buildings to take in the CO2 emissionsand release O2Trees are also planted along highways to reduce noisePhotosynthesis- the process by which energy from light (radiant energy) is used to make carbohydratesHighly endergonic process- using low energy compounds to make an energy- rich compoundCO2 is reduced, and water is oxidized∆G=+685kCal/molEnergy products: 18 ATP and 12 NADPH will be used up to create carbohydrates 1. Light energy (energy from photons) creates this ATP and NADPHPrimary producers are autotrophs, and since we are studying photosynthesis, we will focus on photoautotrophsPhotoautotrophs are organisms that have the capacity to convert radiant energy into chemical energy 1. Includes certain bacteria, algae, and plants 2. “The food we eat and the air we breathe can be traced back to the chloroplast”There are 4 major players of photosynthesisChloroplasts- organelle in which photosynthesis takes placeLight and the electromagnetic spectrum- light travels in the form of waves and is very important in photosynthesisPigments; including chlorophyll A and B as well as carotenesNADP+- this is a coenzymePhotophosphorylation- energy from light is used to phosphorylate an ADP to get ATPChloroplasts have two membranes, but we don’t focus on themThylakoids- third membrane-bound structure in the chloroplasts that are disc-like 1. Usually 1-2 dozen 2. Inside the thylakoid membrane are pigments and proteins essential for light reactions3. Inside the thylakoid lumen is where oxygen is synthesizedThylakoids are arranged in a column called a granum (many grana) 1. Two grana are connected by lamella
Stroma surrounds these structures 1. Inside the stroma are enzymes that reduce CO2 and oxidize water to give carbohydratesChloroplasts are present inside a tissue system called centromesophyll 1. The mesophyll will have about 30-40 chloroplastsTiny openings in leaves called stomata allow CO2 to enter the leaf while releasing water and O2Two different reactions take place; light reactions and dark reactionsLight reactions require sunlight 1. The venue for light reactions is the thylakoid membrane 2. Pigments and proteins here aid in these reactions 3. As a result of light reactions, the energy of photons is converted into ATP and NADPH; both of which will be released into the stromaDark reactions can take place in the presence and absence of light 1. This is the process by which carbohydrates are made inside the stromaOnly a small section of the electromagnetic spectrum is visible to us; we call this the visible spectrumThe visible spectrum’s wavelength extends from 380 nm – 740 nm 1. AKA the Photosynthetically Active RegionLight travels in the form of waves, and when we observe these waves we look at wavelength; the distance from one crest to the next crest on a wave 1. Light contains photons- fast moving particles with unique pockets of energy2. We can tell how much energy a photon has by observing its wavelength 3. The longer the wavelength, the lower the energy potential of the photon (inverse relationship) a. Photons of very short wavelengths have maximum energy potential b. Between red and violet on the visible spectrum, violet has more energybecause it has shorter wavelengthsSometimes photons simply pass through the plant, sometimes they reflect and have no effect, and sometimes they disappear into the pigmentWhen the pigment absorbs this photon, it is said that the delocalized electron is charged 1. In the head of a pigment, an electron is constantly moving between the different atoms of the head2. When the photon hits the head of the pigment, the photon charges this delocalized electronWhen an electron is charged by a photon, it reaches an excited state 1. The excited state is not stable; the electron will always fall back down to the ground state2. Electrons can only be energized to their potential; they will not keep jumping energy levels as they are hit by photonsPlants are green because they absorb all wavelengths except for green
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