B4b: Photosynthesis

Virtually everything we eat can be traced back to plants. Either we eat food from plants or we eat food from animals, that in turn have eaten plants. This item looks at how plants make food in the first place and what they do with it. 

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What is the word equation for photosynthesis?
Carbon dioxide + water = (chlorophyll and light energy) = Oxygen + Glucose.
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What is the waste product in photosynthesis?
Oxygen.
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How do plants use glucose?
They transport it as soluble sugars and store it as insoluble starch.
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What can glucose and starch be converted too?
Other substances in the plant to be used for energy, growth and storage products.
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Why do plants grow faster in summer?
More light and warmth.
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Do plants carry out respiration?
Yes.
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What is the balance symbol equation for photosynthesis?
6COˇ2 + 6Hˇ2O = (light energy and chlorophyll) = 6Cˇ2 + Cˇ6Hˇ12Oˇ6
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What did Greek scientists believe about photosynthesis?
That plants gained mass only by taking in minerals from the soil, however they would have never tested this.
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Who's experiment showed that plants released oxygen? How did he do this?
Joseph Priestly. He put a mint plant in a closed container with a lit candle. The plant used the oxygen up and went out. 27 days later he relit the candle proving that produce a gas that allows fuels to burn.
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What did Jan Baptist van Helmont conclude from his experiment? What was his experiment?
Plant growth cannot be purely due to nutrients in the soil. He grew a willow tree in a weighed amount of soil. 5 years later the tree weighed 74kg more than it did before. As the soil weight had hardly changed he concluded there must be other factors
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What are the stages of photosynthesis?
Light energy is used to split water, releasing oxygen gas and hydrogen ions, and carbon dioxide gas combines with the hydrogen to produce glucose.
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Explain the two experiment using isotopes have increased our understanding of photosynthesis.
Plants watered with water containing ^18O atoms release oxygen gas containing ^18O atoms and Plants supplied with carbon dioxide containing 18O atoms do not release oxygen gas containing 18O atoms. This tells us that oxygen gas comes from water.
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What other substances (6) in plants can glucose and starch be converted to?
Glucose for energy through the process respiration, cellulose for cell walls, proteins for growth and repair, and oils and fats (lipids) stored in seeds, and starch for storage in roots, stems and leaves.
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Why are insoluble substances such as starch are used for storage?
They do not move away in solution from storage areas and they do not affect water concentration inside cells.
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How can photosynthesis rates be increased?
More carbon dioxide, more light and higher temperature.
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Explain carbon dioxide concentration and its effect on photosynthesis.
Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide.
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Explain light intensity and its effect on photosynthesis.
Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis.
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Explain temperature and its effect on photosynthesis.
If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot.
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Why do plants respire all the time?
Plants respire all the time because their cells need energy to stay alive.
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How is glucose used to make proteins?
It is combined with nitrates to make amino acids, which are then made into proteins.
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Why is starch stored?
Ready for use when photosynthesis isn't happening (at night)
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Other cards in this set

Card 2

Front

What is the waste product in photosynthesis?

Back

Oxygen.

Card 3

Front

How do plants use glucose?

Back

Preview of the front of card 3

Card 4

Front

What can glucose and starch be converted too?

Back

Preview of the front of card 4

Card 5

Front

Why do plants grow faster in summer?

Back

Preview of the front of card 5
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