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Lecture 10

Lecture 10 - Chloroplasts and Mitochondria - February 12.docx

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BIOL 2021
Patricia Lakin- Thomas

February 12, 2013 Lecture 10: Chapter 14 – Chloroplasts and Photosynthesis Chloroplasts and Photosynthesis  Chemiosmosis and electron transport  Functions of membranes o Maintain ion gradients o For energy conversion and signalling  Chemiosmosis – energy conversion using a membrane o Chemi = ATP synthesis o Osmosis – membrane transport o Figure 14.1  Electron transport coupled proton pumping  Proton gradient used to make ATP + o H gradients for ATP synth, active transport and bacterial locomotion (fig 14.3 b) Mitochondria vs. Chloros  Mito o Fat + carb + O2  CO2 + H2O  Chloros o H2O + CO2  carbs + O2  Look at fig 14.37  Chloroplast envelope has an outer membrane that is essentially permeable (small molecules) o Inter membrane space o Inner membrane – not so permeable – transporters (transport proteins)  Mitochondrial Matrix = Chloroplast Stroma o Metabolic enzymes o Own DNA, own RNA, ribosomes  BUT in the Chloroplast we have: o Thylakoid membrane  Electron transport – light capturing proteins – ATP synthase o Thylakoid space o Granum (pl. grana)  Stack of thylakoids Light Reactions  Figure 14.38  Photosynthetic electron transfer – sunlight  electron transfer  Products: H2O + NADP  0.5 O2 + NADPH + H+  H+ pumping  ATP synthesis Dark Reactions – still during the day  C fixation  Figure 14.38  3 CO2 + 9ATP + 6NADPH + water  G-3P + 9ADP + 8Pi + 6NADP+  G3P  sugar, fatty acids, amino acids = carbon skeletons Photosynthetic electron transfer  Figure 14.42 – EXAM  Chlorophyll: o Porphyrin ring + Mg + Hydrophobic tail o Absorbs photons, causes electrons to move higher energy orbital  Energy transfer in two ways: o Resonance energy transfer to neighbor chlorophyll, Electrons do not more o Electron transfer  electron transfer, high energy electron from chlorophyll to electron acceptor o Lower energy electron from donor to chlorophyll Photosystems  Figure 14.43  Antenna complex + photochemical reaction centre  Antenna complex – proteins (light harvesting complexes) + chlorophyll  Photochemical reaction centre – proteins + chlorophyll special pair o Excited electrons transferred to acceptors o Lower energy electron r
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