Photosynthesis
Übersicht
Weigh a young oak sapling, plant it, come back thirty years later and weigh the tree. It has gained tonnes. Dig up the soil around it and weigh that too: almost nothing has gone. So where did the tree come from? Overwhelmingly, from thin air and rainwater, assembled by a reaction that runs on sunlight inside the green cells of its leaves.
This lesson takes you through that reaction. You will write the equation for photosynthesis, find out exactly what chlorophyll does with the light it catches, and learn why the rate of the reaction so often stalls even in bright sun. You will then take that idea into the laboratory, where a single stem of pondweed in a tube of water lets you measure the rate for yourself and prove which of three conditions is the one holding everything back.
Ziele
- Photosynthesis is represented by the equation: light carbon dioxide + water → glucose + oxygen
- During photosynthesis: light is absorbed by a green substance called chlorophyll, which is found in chloroplasts in some plant cells and in algae; light is used to convert carbon dioxide (from the air) and water (from the soil) into sugar (glucose); oxygen is released as a by-product.
- The rate of photosynthesis may be limited by: low temperature; shortage of carbon dioxide; shortage of light. These factors interact and any one of them may be the factor that limits photosynthesis. Required practical: Investigate how variables affect the rate of photosynthesis.
Mindmap
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Lektionshinweis
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Unterrichtsbewertung
Herzlichen Glückwunsch zum Abschluss der Lektion über Photosynthesis. Jetzt, da Sie die wichtigsten Konzepte und Ideen erkundet haben,
Sie werden auf eine Mischung verschiedener Fragetypen stoßen, darunter Multiple-Choice-Fragen, Kurzantwortfragen und Aufsatzfragen. Jede Frage ist sorgfältig ausgearbeitet, um verschiedene Aspekte Ihres Wissens und Ihrer kritischen Denkfähigkeiten zu bewerten.
Nutzen Sie diesen Bewertungsteil als Gelegenheit, Ihr Verständnis des Themas zu festigen und Bereiche zu identifizieren, in denen Sie möglicherweise zusätzlichen Lernbedarf haben.
- Which substance absorbs the light used in photosynthesis? A. Cellulose B. Chlorophyll C. Starch D. Glucose Answer: B
- Which is the correct word equation for photosynthesis? A. glucose + oxygen -> carbon dioxide + water B. carbon dioxide + water -> glucose + oxygen C. carbon dioxide + oxygen -> glucose + water D. glucose + water -> carbon dioxide + oxygen Answer: B
- In which organelle does photosynthesis take place? A. Mitochondrion B. Nucleus C. Chloroplast D. Ribosome Answer: C
- A graph of rate of photosynthesis against light intensity becomes horizontal at high light intensities. What does the horizontal section show? A. The plant has stopped photosynthesising B. Light intensity is the limiting factor C. A factor other than light intensity is limiting the rate D. The enzymes have been denatured Answer: C
- Water plants growing 4 m below the surface of a warm lake photosynthesise more slowly than plants of the same species just below the surface, although the temperature and the dissolved carbon dioxide concentration are the same at both depths. What is the most likely limiting factor at 4 m? A. Water B. Carbon dioxide concentration C. Light intensity D. Temperature Answer: C
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