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4.1 Photosynthesis 7.1.d Students know that mitochondria liberate energy for the work that cells do and that chloroplasts capture sunlight energy for photosynthesis. Sources of Energy • ALL cells need energy! • Photosynthesis- process by which a cell captures energy in sunlight and uses it to make food • Key Concept: “Nearly all living things obtain energy either directly or indirectly from the energy of sunlight captured during photosynthesis." • Autotroph- organism that makes its own food • Heterotroph- organism that cannot make its own food Sources of Energy The Two Stages of Photosynthesis Stage 2 The captured light energy is used to produce sugars and oxygen from water and carbon dioxide. Carbon dioxide enters the leaf through openings called stomata Water inters the plant through roots and moves upward to the leaves Key Concept: “During photosynthesis, plants and some other organisms use energy from the sun to convert carbon dioxide and water into oxygen and sugars.” Sugar produced are used by the plant cells for energy Oxygen exits through the stomata on the underside of the leaf. The Two Stages of Photosynthesis • Photosynthesis takes place in 2 stages: capturing sunlight and producing sugar • Pigments- colored chemical compounds that absorb light • Chlorophyll- main photosynthetic pigment in chloroplasts • Chloroplasts- are the green organelles in plant cells that give the plant its color • Chlorophyll is like solar “cells” or cells that capture the energy in light in a calculator • The captured light is used to power the second stage The Two Stages of Photosynthesis • 2 raw materials needed for stage 2 are water and carbon dioxide • Roots absorb water, water then moves up through stem to the leaves, carbon dioxide enters through the stomata • Once the water and carbon dioxide are in the leaf they move into the chloroplasts • Stomata- small openings on the underside of leaves • In the chloroplasts the water and carbon dioxide go through chemical reactions • These chemical reactions are powered by the energy captured in stage 1 • One important byproduct of this chemical reaction in oxygen and exits through the stomata The Two Stages of Photosynthesis • The Photosynthesis equation: Sugar Light energy Oxygen 6CO2 + 6H2O → C6H12O6 + 6O2 Carbon Dioxide Water The Photosynthesis Process Activity • Click the Active Art button to open a browser window and access Active Art about the photosynthesis process. Review How does the sun supply living things with the energy they need? What happens during the process of photosynthesis?