Unit 3 - Key Area 3 - Photosynthesis Flashcards
What is photosynthesis?
Photosynthesis is a series of enzyme-controlled reactions which allow green plants to make sugar.
What is the energy change that takes place during photosynthesis?
Photosynthesis changes light energy from the sun into chemical energy which is stored in the sugar molecules produced.
What are the stages of photosynthesis?
Stage 1 – Light Reaction
Stage 2 – Carbon Fixation
Where does photosynthesis occur?
Photosynthesis takes place inside the chloroplasts of plant cells. Chlorophyll, the green pigment found in chloroplasts, traps light energy, usually from the sun.
What happens during light reaction
Light energy is converted into chemical energy which is used to generate ATP.
The light energy is used to split water into Hydrogen and Oxygen.
Oxygen diffuses from the cell and is released to the air (as a by-product).
ATP and Hydrogen are passed onto the second stage of Photosynthesis (Carbon Fixation).
It takes place in chloroplasts and requires light and chlorophyll.
The raw materials are water (from soil via roots) and light energy.
The products are hydrogen, oxygen, and ATP.
What happens during carbon fixation
A series of enzyme-controlled reactions which use hydrogen and ATP (produced in the light reactions) fuse with carbon dioxide to produce sugar.
It takes place in chloroplasts and does not require light or chlorophyll.
The raw materials are carbon dioxide (from air via stomata), hydrogen, and ATP.
The products are sugar.
What is the chemical energy in sugar available for?
- Converted to an energy source (in respiration)
- Stored as Starch (storage)
- Made into Cellulose (structural)
What are controlled variables? Give examples
These are the variables which stay the same. In this experiment they would be –
• The Water
• The Equipment Size e.g. test tube, funnel
• The time it is left for
• The light being provided
• Temperature
• pH
What are independent variables? Give examples
There are the variables which are changed. In this experiment they would be –
• The Type of Plant
What are dependent variables? Give examples
These are the variables in which change is measured. In this experiment they would be –
• The Number of Bubbles Produced
How can you make experiments more reliable?
By repeating it at least 3 times and calculating the average
What is reaction rate?
Reaction rate is the speed at which a chemical reaction proceeds.
It is shown as the concentration of a product formed or the concentration of reactant used up within a unit of time.
How can be measure the rate of photosynthesis?
The rate of photosynthesis is measured by counting the number of oxygen bubbles released by Elodea (water plant) over a unit of time.
The more bubbles, the higher the rate of photosynthesis.
What is the effect of a limiting factor?
During an experiment to investigate factors which effect the rate of photosynthesis only one variable can be changed at a time. E.g. light intensity
As the investigated factor increases, other factors which affect the rate of photosynthesis become limited.
These limiting factors prevent a continual increase in photosynthetic rate.
Limiting factors are carbon dioxide concentration, light intensity, and temperature.
They can limit plant growth.
Name the three limiting factors of photosynthesis
Light Intensity
Carbon Dioxide Concentration
Temperature
