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Chapter 10 - Chapter 10 Photosynthesis Life on earth is...

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Chapter 10- Photosynthesis Life on earth is solar powered. Photosynthesis is the process where plants capture light from the sun and convert it into chemical energy stored in sugar and other organic molecules. Autotrophs produce their organic molecules from carbon dioxide and other raw inorganic molecules obtained from the environment. They are the first source of organic compounds and are name producers. Almost all plants photo autotrophs, as they use light energy to synthesize their organic substances Photosynthesis also occurs in some prokaryotes, algae and protists. Heterotrophs are unable to make their own food and live on compounds produced by other organisms. They are consumers. Heterotrophic nutrition can be animals eating plants and other animals as well as organisms feeding on the remains of dead organisms (decomposers). Almost all heterotrophs are completely dependent on photoautotrophs for food and also for oxygen. Chloroplasts: All green parts of plants including green stems and un-ripened fruits have chloroplasts. There are about half a million chloroplasts per square millimetre of a leaf’s surface. Chlorophyll is the green pigment that gives the leaf colour. Light energy is absorbed by chlorophyll and drives the synthesis of organic compounds in the chloroplasts. Chloroplasts are usually found in the mesophyll layer. A typical mesophyll cell contains 30-40 chloroplasts each measuring 2-4 micrometers by 4-7 micrometers. The stoma (stomata) is the pore where gases diffuse into and out of the leaf. Water is absorbed by the roots and delivered to the leaves via veins. Veins are also used to export sugar to the roots and other non-phtotosynthetic parts of the cell. The stroma is the dense fluid within the chloroplast. It is held in place by an envelope of 2 membranes. The thylakoids are membranous sacs interconnected into an elaborate system. These separate the stroma from its interior called the thylakoid space. The thylakoids are stacked in columns called grana (singular granum). Chlorophyll is stored in the thykaloid membranes. Photosynthesis: In the presence of light, green parts of plants produce organic compounds and oxygen from carbon dioxide and water. Equation: 6 CO 2 + 12 H 2 O + Light Energy C 6 H 12 O 6 + 6 O 2 + 6 H 2 O Net consumption of water: 6 CO 2 + 6 H 2 O + Light Energy C 6 H 12 O 6 + 6 O 2 *The overall chemical change is the reverse of the one that occurs in cellular respiration. Splitting of water:
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Assuming that the simplest carbohydrate is made, the equation becomes: CO 2 + H 2 O [CH 2 O] + O 2 It is known that the oxygen given off from photosynthesis is derived from water and not from carbon dioxide. The splitting of water by chloroplasts releases this oxygen as well as hydrogen.
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