MCB 181 1st Edition Lecture 17Outline of Previous Lecture I. FermentationII. Clicker QuestionsOutline of Current Lecture I. OverviewII. ChloroplastsIII. Clicker QuestionsCurrent LectureI. Overviewa. The chemical reaction of photosynthesis is:CO2 + 2 H2O + light energy (CH20)n + H2O + 2 Sb. Photosynthesis is made by two linked sets of reactionsi. Light dependent reactions – produces oxygen, ATP, and NADPHii. Light independent reactions – it produces sugar from carbon dioxideII. Chloroplastsa. Structure of a chloroplasti. Thylakoids are vesicle-like structuresii. Often the thylakoid are interconnected in stacks called granaiii. Lumen is the internal space in the thylakoidiv. Stroma is the fluid-filled space between the thylakoids and the inner membranev. Pigments are molecules capable of absorbing certain wavelengths of lightb. Both chlorophyll a and b have the same structurei. A long tail of isoprene subunitsii. A head which is a large structure with a magnesium atom in its centeriii. The tail keeps the molecule embedded in the thylakoid membraneiv. The head is where the light is absorbedc. Photosystemsi. In the thylakoid membrane between 200-300 chlorophyll molecules and accessory pigments are grouped together in an array of proteinsii. This complex is known as a photosystemiii. Photosystems have two major elements1. An antenna complex2. The reaction centerd. The three fates of excited electrons in photosynthetic pigments:e. What happens in the reaction center?i. When the energy of the reaction reaches the reaction center of a photosystem, excited electrons are transferred to a molecule that acts as an electron acceptorii. When this molecule becomes reduced absorption of light becomes permanentiii. At this point we can say that electromagnetic energy has become chemical energyf. Electron Transport Chaini. Once pheophytin is reduced, the electron is transferred to an electron transfer chainii. This ETC is similar in structure and function to the ETC studied in cellular respirationIII. Clicker QuestionsAssertion ReasonWhile cellular respiration consists of oxidizing glucose to obtain ATP, photosynthesis consists of reducing carbon dioxide to synthesize glucoseBecausePhotosynthesis is a catabolic pathway while cellular respiration is an anabolic pathwayAssertion is true; Reason is false.Assertion ReasonPlastoquinone is a lipid soluble molecule, which connects a photosystem II and I when it transfers electrons.BecauseThe electrons brought by plastoquinone are used to stabilize photosystem I.Assertion is true; Reason is true; Reason is NOT the correct
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