BMB 251 1st Edition Lecture 38 Outline of Last Lecture I. Golgia. Cis faceb. Trans faceII. Lysosomes III. MitochondriaIV. ChloroplastV. Cellular Respirationa. Glycolysisb. Citric acid cyclec. Electron transport chainOutline of Current Lecture VI. Clicker QuestionsVII. Photosynthesisa. Light dependent reactionsb. Light independent (Calvin) reactionsVIII. Oxidative Phosphorylation vs. PhotophosphorylationCurrent Lecture- Clicker Question 1: the ETC has three compartments, which one binds the electron of the highestfree energy?o NADH dehydrogenase complex (first complex of the three)- Clicker Question 2: Which of the following does not occur in the chloroplastso Oxidative phosphorylation- Photosynthesis: converts light energy to create the most familiar source of energy-glucose; it creates this through two reactionso Light dependent reactions: use photons to split water molecules, and generates ATP from sending the stripped electrons from the oxygen molecule down an ETCo Light independent reactions: generates reduced carbon molecules via carbon fixation, which then become sugars that help to store the free energy in ATP- Chloroplasts have three subcompartments: matrix space, intermembrane space and thylakoid space, which is surrounded by thylakoid membraneo Protein transport here resembles that of mitochondria: both occur post-tanslationally, use separate translocation complexes in each membrane, require energy, and use amphiphilic N-terminal SS that are removed afterwardo Chloroplast use GTP and ATP hydrolysis to power import across double membrane instead of H+ gradient These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Thylakoid: house protein subunits of photosynthesis system and of ATP synthase First proteins pass across double membrane at special contact sites to get to matrix space (known as stroma in chloroplasts) and then translocate into either thylakoid membrane or space Contains the two photosystems, the ETC and is the site where ATP synthesis occurs through ATP synthaseo Stroma: analogous to the mitochondrial matrix. This is the site of light independent (dark reactions), the Calvin cycle and carbon fixation- Light dependent reactions:o Sunlight travels in little packets of energy, called photonso These photons can either reflect (bounce) off of a leaf, or can be absorbed by the leaf viapigments ( compounds that absorb light at a specific wavelength)o Pigments absorb the light and the energy raises electrons to a higher energy stateo Electrons become unstable and are then passed on to a specialized chlorophyll molecule at the center of photosystem IIo These electrons are then passed onto the ETCo **There are two ETCs in photosynthesis, which are connected to one another to create the “Z-scheme” (process of moving electrons through photosystem I and then photosystem II)o Water acts as the source of electrons used in photosynthesis; protons and oxygens are released as by-productso Energy released in the redox of ETC is used in two ways: Electrons going through ETC I release energy, which is used to move protons across the thylakoid membrane (protons in the thylakoid space create voltage, which is used by ATP synthase to produce ATP) Electrons going through ETC II reduce NADP+ to NADPH **These two products (ATP and NADPH) are then used to make sugar, which happens in the light-independent reactions **Photophosphorylation: ATP synthase takes energy from photons moving across membrane to make ATP from ADP and PO4- Light independent reactions (Calvin Cycle):o There is no chlorophyll or photons used hereo The Calvin cycle is where the stored energy (from ATP and NADPH) from the ETCs are used to form sugar from CO2o Anabolic and endergonic reactions occur within the chloroplastso 5-carbon compound (RuBP) combines with CO2 to form highly unstable 6-carbon compound, which immediately splits into two 3-carbon molecules (enzyme rubisco catalyzes this reaction)o 3-carbon compounds are reduced to glyceraldehyde 3-phosphate (G3P), a 3-carbon molecule (the electrons that are added in the reduction process come from NADPH)o At the end of the Calvin Cycle, some G3P leaves the cycle to produce sugar, but most of it is used to regenerate RuBPo **Glucose is not actually created in the Calvin Cycle, but rather the G3P sugar iso G3P is then used by cells as an immediate source or energy to be metabolized in cellular respiration OR can be used to build glucose molecules that will be in used by plant to build cell walls, starches, and other polysaccharides - **The citric acid cycle in cellular respiration regenerates oxaloacetate just like the Calvin cycle must regenerate RuBP to restart the cycle- **Photophosphorylation: making ATP from light- **Oxidative phosphorylation: uses series of oxidation reactions to create ATP via a
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