Flashcards
Photosynthesis
Cards in this deck (39)
- 1How plants gain in mass has been the subject of study for thousands of years. What did the early Greeks think about how plants gained mass?They thought plants gained mass by taking in minerals in the soil.
- 2Who carried out a simple experiment in the 17th century to see how plants gained their mass?Johann Baptiste van Helmont.
- 3What simple experiment did Johann Baptiste van Helmont carry out?He dried out 200lb of earth in a furnace (then moistened it with rainwater) and put it in an earthen vessel. He then placed the stem of a willow tree weighing 5lb in the vessel. After 5 years, the tree had grown to over 169lb. He again dried the earth in the vessel and found it weighed 200lb.
- 4What did van Helmont notice about his experiment?He noticed that the amount of soil in the vessel he used was equal to the amount of soil at the start of the experiment. Therefore he deduced that the tree's weight gain had come form water. As the tree had only received water, he proposed that the weight of wood and other plant material had come from water alone.
- 5What was the one crucial factor that van Helmont missed from his experiment?He missed the crucial factor - the effect of gases in the air.
- 6What do we now know about how a tree gains mass?We now know that a large proportion of the mass of the tree comes from the carbon dioxide in the air, which, together with water, is turned into carbohydrates through photosynthesis.
- 7Who did further experimental evidence of photosynthesis in 1771?Joseph Priestley.
- 8How did Joseph Priestley provide further experimental evidence on photosynthesis?He put a shoot of mint into a closed glass vessel with a lit candle. The candle extinguished very quickly. After 27 days he relit the candle using sunlight focused by a concave mirror. The candle burned again in the air that previously would not support combustion. We now know that the mint shoot had produced oxygen gas.
- 9How do plants make food to grow?They do not absorb food from the soil. They make their own, using sunlight. This is called photosynthesis and it occurs in the cells.
- 10What is needed, what is produced in photosynthesis and where does it take place?Needed:
Light (from sun).
Carbon dioxide (diffused from the air).
Water (from the soil).
Takes place in:
Chlorophyll (in the leaves).
Produced:
Glucose (for biomass and energy).
Oxygen (released as a by-product) - 11What is the word equation for photosynthesis?Carbon dioxide + water = Glucose + oxygen
- 12What is the symbol equation for photosynthesis?6CO2 + 6H2O = C6H12O6 + O6
- 13What is needed to convert the CO2 and water to glucose and oxygen?Light.
Chlorophyll. - 14What is the glucose produced in photosynthesis used for?It is used immediately to produce energy through respiration. Some of this energy is used to build up smaller molecules into larger molecules.
- 15What does the plant convert glucose into and why?It converts it into starch because starch is an insoluble carbohydrate, which can be stored in cells.
- 16What structure is glucose? What structure is starch?Glucose = Individual sugar molecules.
Starch = Huge, long chain identical sugar molecules - 17What can glucose also be converted into and why?Glucose converts into cellulose, needed by the plant for cell walls.
- 18What structure is cellulose?It is very similar to starch, but the long chains are cross-linked to form a meshwork.
Long chains of sugar molecules held together by weak bonds. - 19What is converted to make proteins?Glucose.
Nitrates.
Other nutrients. - 20Why do plants need proteins?For growth and repair and also to make enzymes.
- 21Describe the equation for getting protein in plants.Glucose + nitrates = lots of amino acids = Proteins (huge, long chains of different amino acids)
- 22What else can glucose be converted into and why?It can be converted into Lipids (fats or oils) to store in seeds.
- 23What is glucose transported as and stored as?The glucose made in photosynthesis is transported as soluble sugars but is stored as insoluble starch.
- 24Why is starch a very useful storage molecule?It is insoluble so it does not affect the concentration inside the cells where it is stored.
- 25Why do the cells not store soluble glucose?Because then the inside of the cells would become very concentrated and water would constantly move in, which would make the cell swell. In addition, the carbohydrate would move away in solution from storage areas.
- 26Why does plant growth slow down or even stop in winter?Because plants need light and warmth and in winter there is a lack of sunlight and warmth.
- 27Plant growth can be artificially increased by growing plants in greenhouses. What does this enable?The temperature to be increased by using heaters.
The light intensity to be increased by using lamps.
The carbon dioxide concentration to be increased by using chemicals or as a by-product of the fossil fuel heaters. - 28What are the two stages to photosynthesis?1) Light energy is used to split water, releasing oxygen gas and hydrogen ions:
water = oxygen + hydrogen ions.
2) Carbon dioxide gas then reacts with the hydrogen ions to make glucose and water:
carbon dioxide + hydrogen ions = glucose (+ water). - 29How were radioactive isotopes used to discover the source of oxygen in photosynthesis in early experiments?A plant was given a special type of water called 'heavy water'. It was allowed to absorb this through its roots. Heavy water contains the heavier oxygen atom with an atomic mass of 18 (rather than 16). The plant was allowed to absorb atmospheric carbon dioxide as usual.
- 30What did this experiment show?The heavier oxygen atom was traced and it was found to be present in the oxygen that was released from the leaves of the plant.
It was concluded that none of the evolved oxygen came form carbon dioxide initially taken in by the plant. - 31Why do all living organisms respire?To supply their cells with the energy they need to work, grow and reproduce.
- 32What do plants use oxygen for?They take in oxygen and break it down into glucose to release energy.
Plants carry out respiration continually. - 33What factors can limit the rate of photosynthesis?Temperature.
Carbon dioxide concentration.
Light intensity.
( At any particular time, any one of them may be the limiting factor). - 34Describe the effect of temperature on photosynthesis?1) As temp rises so does rate of photosynthesis. This means temp is limiting the rate of photosynthesis.
2) As temp approaches 45oC; enzymes controlling photosynthesis start to be destroyed and rate of photosynthesis declines to zero. - 35Describe the effect of carbon dioxide concentrations on photosynthesis?1)As rate of carbon dioxide concentration rises so does rate of photosynthesis. So carbon dioxide is limiting rate of photosynthesis.
2) Rise in carbon dioxide levels now has no effect. Carbon dioxide is no longer the limiting factor; therefore, light or temp must be. - 36Describe the effect of light intensity on photosynthesis?1) as light intensity increases so does rate of photosynthesis. This means light intensity is limiting the rate of photosynthesis.
2) Rise in light intensity now has no effect. Light intensity is no longer the limiting factor; carbon dioxide or temp must be. - 37During the night the plants continue to respire. What is respiration a reverse of?Photosynthesis.
- 38What do plants do during the day?They respire constantly, but they also photosynthesise at a much greater rate, using up the carbon dioxide produced from respiration and giving out oxygen.
- 39What do plants do during the night?The absence of light means that plants cannot photosynthesise, but they continue to respire.
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- GCSE biology (B4) Flashcards on Photosynthesis, created by Rebecca Smith on 08/04/2017.
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- Rebecca Smith
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