Photosynthesis Flashcards
All 18 cards in this deck
What is the word equation for photosynthesis?
carbon dioxide + water glucose + oxygen (light energy needed)
Which structure in a plant cell is the site of photosynthesis?
The chloroplast.
Name the green chemical in chloroplasts that absorbs light.
Chlorophyll.
Why is photosynthesis described as an endothermic reaction?
It takes in energy — light energy is transferred to the plant from the surroundings.
Why are photosynthetic organisms (plants and algae) called the main producers?
They make food (glucose) and therefore biomass that other organisms depend on.
True or false? Oxygen is a reactant in photosynthesis.
False. Oxygen is a product; the reactants are carbon dioxide and water.
What is a limiting factor of photosynthesis?
A factor that is in short supply and so holds back the rate of photosynthesis.
What happens to the rate of photosynthesis as light intensity increases (before any other factor limits it)?
The rate of photosynthesis increases (more bubbles of oxygen per minute).
What is the effect of a very high temperature, such as 60°C, on photosynthesis?
Photosynthesis stops, because the enzymes are denatured.
What happens to the rate of photosynthesis as carbon dioxide concentration increases, while it is the limiting factor?
The rate increases, until another factor becomes limiting.
True or false? Fewer small plants grow on a woodland floor where light intensity is low because they cannot photosynthesise enough.
True. Low light limits photosynthesis, so fewer plants per m² survive.
True or false? At high temperatures the enzymes used in photosynthesis are killed.
False. Enzymes are denatured — they are not alive, so they cannot be killed.
In the core practical with pondweed, how is the rate of photosynthesis measured?
Count the number of bubbles (or measure the volume of oxygen) produced in a set time.
Give two ways to improve the quality of results when the oxygen bubbles are hard to count.
Collect the gas in a syringe/measuring cylinder and measure its volume; or repeat at each light intensity and calculate a mean.
How is temperature kept constant in the light intensity core practical?
Use a heat shield between the lamp and the tube, and a thermometer, adding cold water as necessary.
Name the three limiting factors of photosynthesis.
Light intensity, carbon dioxide concentration and temperature.
In the light intensity core practical, how is the light intensity reaching the pondweed changed?
By moving the lamp to different distances from the pondweed: the further away the lamp, the lower the light intensity.
Why is sodium hydrogencarbonate added to the water in the light intensity core practical?
It releases carbon dioxide, so CO₂ is not a limiting factor and stays the same at every light intensity.