Photosynthesis
What is the word equation for photosynthesis?
Carbon dioxide + water + light --> glucose + oxygen
What happens to the rate of photosynthesis as light intensity increases?
It increases
What is the chemical that absorbs light and when in the plan is it found?
Chlorophyll in chloroplasts
What is the independent variable in an experiment testing light intensity and photosynthesis rate?
Light Intensity
Which part of the plant carries out the most photosynthesis?
A. Leaves
B. Stem
C. Roots
D. Flowers
A. Leaves
In which organelle does photosynthesis occur?
Chloroplast
What eventually happens to the rate of photosynthesis if light intensity keeps increasing?
It levels off (plateaus/stops increasing).
Which two colours of light are most effective for photosynthesis?
Red and blue
What is one way to measure the rate of photosynthesis in water plants?
Counting oxygen bubbles or measuring oxygen production or measuring CO2 levels or pH of indicator.
What is the function of stomata in photosynthesis?
They allow gas exchange: CO₂ in, O₂ out.
What is the role of chlorophyll in photosynthesis?
It absorbs light energy used to convert carbon dioxide and water into glucose.
Why does the rate of photosynthesis plateau at high light intensities?
Because other factors such as CO₂ concentration or temperature become limiting.
The is green light the least effective for photosynthesis?
Chlorophyll is green so it reflects the green light instead of absorbing it.
Why is it important to have control variables?
To ensure the results aren't affected by anything except the independent variable and keep it a fair test.
Why are leaves broad and flat?
Thin and large surface area for light absorption.
How does the conc. of carbon dioxide affect the rate of photosynthesis, and what happens when it becomes too high?
Increasing carbon dioxide concentration generally increases the rate of photosynthesis, up to a point. Beyond that, the rate levels off because another factor (like light or temperature) becomes limiting.
How would doubling the light intensity affect the rate of photosynthesis if no other factors were limiting?
The rate would approximately double.
How would you design an experiment to test the effect of different wavelengths on photosynthesis?
Use coloured filters, same plant species, same light intensity and duration, and measure oxygen production/bubble count/amount of CO2.
Why should you compare your results to another photosynthesis experiment?
To support or argue against your results. (Showing the pattern is unusual or expected)
How do guard cells help regulate photosynthesis?
They open and close stomata to control CO₂ intake and water loss.
Explain how the light-dependent and light-independent stages of photosynthesis are connected.
The light-dependent reactions produce energy (ATP and NADPH), which are used in the light-independent reactions to fix carbon dioxide into glucose.
A plant is exposed to high light intensity but the rate of photosynthesis decreases. Give one possible biological explanation.
Photoinhibition may occur, where excessive light damages the photosystems.
Explain how the absorption spectrum of chlorophyll relates to the action spectrum of photosynthesis.
The absorption spectrum shows which wavelengths chlorophyll absorbs best, which matches the wavelengths where the rate of photosynthesis is highest in the action spectrum.
Suggest two ways to improve the accuracy of a photosynthesis investigation.
Use a gas sensor instead of counting bubbles/using an indicator.
Ensure consistent light distance with a lux meter.
How do the xylem and phloem work together to support photosynthesis in a plant?
Xylem transports water from the roots to the leaves, which is needed for photosynthesis. Phloem transports the glucose produced in the leaves to other parts of the plant for storage or energy.