Photosynthesis - The LIMITING factors

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What is the law of limiting factors?
When a process is affected by a number of factors, the factor in the shortest supply at a given time determines the rate of the overall process.
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What are the key limiting factors?
Light quality and intensity, CO2 concentration, temperature, water and nutrients.
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What effect does low light intensities have on the rate of photosynthesis?
As light intensity increases, so does the rate of photosynthesis and is a limiting factor.
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What is the effect of high light intensities on photosynthesis rate?
Rate of photosynthesis plateaus and light is no longer a limiting factor as it doesn't affect the rate.
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What does increasing CO2 do to the rate of photosynthesis?
Increasing CO2 increases rate of photosynthesis as CO2 is a substrate for photosynthesis.
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What happens after a certain point is reached?
The rate of photosynthesis plateaus.
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What happens to the rate of photosynthesis as temperature is increased?
Rate increases to its optimum as temperature increases. After, a too high temp will denature enzymes and rate will decrease.
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What are the 3 main effects that light has?
Causes stomata to open so CO2 can enter the leaves. Trapped by chlorophyll where it excites electrons. Splits water to produce protons.
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Which stage is likely to be enzyme controlled and which is not?
Light independent is enzyme controlled and the light dependent is not.
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When is a stage more likely to be enzyme controlled?
When light is not limiting and so it is temperature dependent. An increase in temperature and a decrease in photosynthesis rate.
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What shows a stage is not likely to be enzyme controlled?
When limited by light and temperature insensitive.
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What are the ways that photosynthesis rate can be measured?
Measuring volume of oxygen produced in a given time. Measuring volume of CO2 uptake. Measuring rate of increase in dry mass in plant.
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What are the limitations of measuring volume of oxygen to determine photosynthesis rates?
Some oxygen produced will be used in respiration and there may be dissolved nitrogen in the gas collected.
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Describe the process to investigate effect of light intensity on rate
1. Fill apparatus with tap water. 2. Cut piece of plant+place in test tube. Add hydrogencarbonate solution. 3. Place light close to beaker. 4. Note length of bubble. 5. Repeat 4 2x more.6. Move light further away. 7. Test with different intensities.
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How does increasing light intensity affect rate in Calvin Cycle?
Alters light-dependent reaction. More light=more energy to excite more electrons. Produces more ATP and NADPH produced.
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What would the effect of low light intensities be on the Calvin Cycle?
Less/no light=no light dependent stage. GP not converted to TP so no RuBP can be regenerated. GP builds up and TP levels fall.
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What effect does increasing levels of CO2 have on the Calvin Cycle?
More CO2=more fixation. More fixation=more GP produced meaning more TP produced and RuBP can be regenerated.
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What happens if CO2 levels are low in the Calvin Cycle?
RuBP will accumulate and levels of GP and TP will fall.
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What does the number of stomata open cause?
More transpiration and wilting of the plant. Leads to stress response and stomata close. Reduces CO2 uptake and decreases rate of photosynthesis.
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What effect does increasing temperature have on the light dependent stage?
Not a large effect as light dependent stage is not controlled by enzyme reactions.
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What will increasing temperature affect the rate of?
The light independent stage which is enzyme controlled. Increases the rate.
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What will happen if the temperature rises too much?
Photorespiration exceeds photosynthesis which wastes ATP and NADPH.
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Card 2

Front

What are the key limiting factors?

Back

Light quality and intensity, CO2 concentration, temperature, water and nutrients.

Card 3

Front

What effect does low light intensities have on the rate of photosynthesis?

Back

Preview of the front of card 3

Card 4

Front

What is the effect of high light intensities on photosynthesis rate?

Back

Preview of the front of card 4

Card 5

Front

What does increasing CO2 do to the rate of photosynthesis?

Back

Preview of the front of card 5
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