Investigation of Limiting Factors (Cambridge (CIE) A Level Biology): Flashcards
Exam code: 9700
1/190Still learning
Know0
Define limiting factor.
Was this flashcard helpful?
Cards in this collection (19)
Define limiting factor.
A limiting factor is the factor that is in shortest supply and so directly limits the rate of a process such as photosynthesis.
Name three limiting factors of photosynthesis.
Light intensity, carbon dioxide concentration and temperature.
The factor in shortest supply that limits the rate of photosynthesis is called the .
The factor in shortest supply that limits the rate of photosynthesis is called the limiting factor.
How does increasing light intensity affect the rate of photosynthesis?
The rate increases as light intensity rises.
Eventually it plateaus when another factor becomes limiting.
How does increasing carbon dioxide concentration affect the rate of photosynthesis?
The rate increases as CO2 concentration rises, then plateaus when another factor becomes limiting.
How does temperature affect the rate of photosynthesis?
The rate increases up to an optimum as enzyme activity rises.
Above the optimum, enzymes denature and the rate falls.
On a graph, why does the rate of photosynthesis plateau at high light intensity?
Light is no longer limiting.
Another factor, such as carbon dioxide concentration or temperature, has become the limiting factor.
Define redox indicator (in a photosynthesis investigation).
A redox indicator is a dye that changes colour when it is reduced, acting as an electron acceptor in place of NADP.
Name two redox indicators used with a suspension of chloroplasts.
DCPIP and methylene blue.
What colour change occurs when DCPIP is reduced by illuminated chloroplasts?
It changes from blue to colourless.
In the chloroplast suspension method, what does a faster colour change indicate?
A faster rate of the light-dependent reactions, i.e. a faster rate of photosynthesis.
As illuminated chloroplasts reduce it, blue DCPIP turns .
As illuminated chloroplasts reduce it, blue DCPIP turns colourless.
How can the rate of photosynthesis be measured using an aquatic plant such as Elodea?
By counting the oxygen bubbles released, or measuring the volume of oxygen collected, per unit time.
How can light intensity be varied in an investigation using an aquatic plant?
By changing the distance between a lamp and the plant.
Why should a heat shield or water bath be used when varying light intensity with a lamp?
To keep temperature constant, since the lamp also gives out heat.
This stops temperature from becoming a confounding variable.
How can a suspension of chloroplasts and DCPIP be used to investigate the effect of light wavelength on photosynthesis?
Illuminate identical chloroplast and DCPIP mixtures with different colours (wavelengths) of light, using coloured filters and keeping light intensity constant.
Time how long the DCPIP takes to decolourise at each wavelength.
Which wavelengths of light give the fastest decolourisation of DCPIP, and why?
Red and blue light give the fastest rate.
These wavelengths are absorbed most by chlorophyll, so more electrons are released to reduce the DCPIP. Green light is mostly reflected, so the rate is slowest.
How can an aquatic plant be used to investigate the effect of carbon dioxide concentration on the rate of photosynthesis?
Place the plant in solutions containing different concentrations of sodium hydrogencarbonate (a source of carbon dioxide).
Keep light intensity and temperature constant, and count the oxygen bubbles released per minute at each concentration.
How can an aquatic plant be used to investigate the effect of temperature on the rate of photosynthesis?
Place the plant in a water bath at a range of temperatures, keeping light intensity and carbon dioxide concentration constant.
Measure the volume of oxygen produced, or count bubbles, per unit time at each temperature.
Sign up to unlock flashcards
or