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Ebook Cambridge international AS and A level - Biology coursebook: Part 2

(BQ) Part 2 book "Cambridge international AS and A level - Biology coursebook" has contents: Photosynthesis, homeostasis, inherited change, selection and evolution, genetic technology, amino acid R groups,.and other contents. | Cambridge International A Level Biology 286 Chapter 13: Photosynthesis Learning outcomes You should be able to: ■■ ■■ ■■ describe the absorption of light energy in the light dependent stage of photosynthesis explain the transfer of this energy to the light independent stage of photosynthesis and its use in the production of complex organic molecules describe the role of chloroplast pigments in the absorption of light energy ■■ ■■ ■■ discuss how the structure of a chloroplast fits it for its functions explain how environmental factors influence the rate of photosynthesis describe how C4 plants are adapted for high rates of carbon fixation at high temperatures Chapter 13: Photosynthesis Fuel from algae Despite millions of hours of research, we still have not managed to set up a chemical manufacturing system that can harvest light energy and use it to make complex chemicals, in the way that plants and some protoctists do. So, why not just let the cells do it for us? Figure 13.1 shows a photobioreactor – a series of tubes containing the single-celled photosynthetic organism Chlorella. Provide light, carbon dioxide and minerals, and the cells photosynthesise. Bioreactors like this are being used around the world to produce biomass for animal feed, and chemicals that can be used as food additives or in the manufacture of cosmetics. They can also be used to convert energy from the Sun into ethanol or biodiesel but, so far, the bioreactors cannot produce biomass cheaply enough to compete with the use of fossil fuels. Figure 13.1  A photobioreactor. An energy transfer process a ribosomes As you have seen at the beginning of Chapter 12, the starch grain process of photosynthesis transfers light energy into chemical potential energy of organic molecules. This energy can then be released for work in respiration (Figure 12.2). Almost all the energy transferred to all the ATP molecules in all living organisms is derived from light energy used in photosynthesis .