Chapter 10 - Chapter 10 Photosynthesis Chapter 10...

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Chapter 10 - Photosynthesis Chapter 10 Photosynthesis Lecture Outline Overview: The Process That Feeds the Biosphere Life on Earth is solar powered. The chloroplasts of plants use a process called photosynthesis to capture light energy from the sun and convert it to chemical energy stored in sugars and other organic molecules. Plants and other autotrophs are the producers of the biosphere. Photosynthesis nourishes almost all the living world directly or indirectly. o All organisms use organic compounds for energy and for carbon skeletons. o Organisms obtain organic compounds by one of two major modes: autotrophic nutrition or heterotrophic nutrition. Autotrophs produce their organic molecules from CO2 and other inorganic raw materials obtained from the environment. o Autotrophs are the ultimate sources of organic compounds for all heterotrophic organisms. o Autotrophs are the producers of the biosphere. Autotrophs can be separated by the source of energy that drives their metabolism. o Photoautotrophs use light as a source of energy to synthesize organic compounds. Photosynthesis occurs in plants, algae, some other protists, and some prokaryotes. Chemoautotrophs harvest energy from oxidizing inorganic substances, such as sulfur and ammonia. Chemoautotrophy is unique to prokaryotes. Heterotrophs live on organic compounds produced by other organisms. o These organisms are the consumers of the biosphere. o The most obvious type of heterotrophs feeds on other organisms. Animals feed this way. o Other heterotrophs decompose and feed on dead organisms or on organic litter, like feces and fallen leaves. Most fungi and many prokaryotes get their nourishment this way. o Almost all heterotrophs are completely dependent on photoautotrophs for food and for oxygen, a by-product of photosynthesis. Concept 10.1 Photosynthesis converts light energy to the chemical energy of food All green parts of a plant have chloroplasts.
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However, the leaves are the major site of photosynthesis for most plants. o There are about half a million chloroplasts per square millimeter of leaf surface. The color of a leaf comes from chlorophyll, the green pigment in the chloroplasts. o Chlorophyll plays an important role in the absorption of light energy during photosynthesis. Chloroplasts are found mainly in mesophyll cells forming the tissues in the interior of the leaf. O2 exits and CO2 enters the leaf through microscopic pores called stomata in the leaf. Veins deliver water from the roots and carry off sugar from mesophyll cells to nonphotosynthetic areas of the plant. A typical mesophyll cell has 30–40 chloroplasts, each about 2–4 microns by 4–7 microns long.
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Chapter 10 - Chapter 10 Photosynthesis Chapter 10...

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