Light-driven reactions in photosynthesis

Published on April 19, 2020 Reviewed on November 27, 2022   43 min

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Greetings. Welcome to Lecture 19 in our Principles of Biochemistry lecture series. I'm Jerry Feigenson, a professor in the Department of Molecular Biology and Genetics at Cornell University in the USA. In the previous lecture, lecture number 18, you saw how amino acids break down to form nitrogen free useful fuel molecules. In mammals, the various fuels that we eat create a gradient of protons and voltage across the inner mitochondrial membrane by means of four different protein complexes. Then, the ATP synthase enzyme uses these gradients to drive synthesis of ATP from ADP and phosphate.
In this 19th lecture, you will learn some of the basics of chloroplast structure relevant to photosynthesis, and we will see what are the possible four fates for energy in general after light is absorbed. We will see the roles of chlorophyll and other photosynthetic pigments, and we will spend most of the time looking at events in the photosynthetic reaction centers, which create a proton gradient across the thylakoid membrane. Then at the end, we will summarize how the strong reducing power created by light absorption can be simply summarized in what's called the Z scheme.