Unit 4 - Photosynthesis + uses of photosynthesis + rate of photosynthesis Flashcards
What do plants use as their sources of energy
Plants use light for their source of energy
Define photosynthesis
Photosynthesis is the process by which plants make food using carbon dioxide, water and light
The ______ that plant use to trap this ______ energy is called _______
The reaction that plants use to trap this light energy is called photosynthesis
photosynthesis is an _____
reaction in which _______ is transferred from the ________to the
_________by _______.
photosynthesis is an endothermic
reaction in which energy is transferred from the environment to the
chloroplasts by light.
What type of reaction is photosythesis. Why?
Photosynthesis is an example of an endothermic reaction. This is because photosynthesis takes in energy
This means that energy is transferred from the environment in the process
Where does photosynthesis take place
Photosynthesis takes place in the leaves of a plant in the chloroplasts.
What do leaves contain
Leaves contain the green chemical chlorophyll. Chlorophyll can absorb the light energy
Describe the process of photosynthesis
In the first stage of photosynthesis, the plant takes in carbon dioxide and water
Light energy is then absorbed by chlorophyll
This light energy is then used to convert the carbon dioxide from the air and water from the soil into the sugar glucose.
In this reaction oxygen is also produced
Describe the path taken by a carbon atom as it moves from being part of the carbon dioxide in the air to being part of a starch molecule in a plant
Carbon atom moves from air into air spaces in leaf,
into plant cells,
into chloroplasts,
joins with water to make glucose,
and is converted to starch for storage
Explain why photosynthesis is an endothermic reaction
Photosynthesis needs a bigger input of energy from environment
to break bonds holding carbon dioxide and water together
that is released when new bonds form in glucose and oxygen.
Where in the plant does most photosynthesis happen (which tissue)
The palisade mesophyll is the tissue where most photosynthesis happens
State the word equation for photosynthesis
carbon dioxide + water → glucose + oxygen
add the word ‘light’ over the arrow
State the symbol equation for photosynthesis
CO2 +H2O → C6H12O6 +O2
add the word ‘light’ over the arrow
State the factors that affect photosynthesis
Carbon dioxide concentration
Temperature
Light intensity
Amount of chlorophyll in a plant
State the uses of glucose produced by photosynthesis for plants
How plants use glucose
The glucose produced in photosynthesis may be:
- used for respiration
- converted into insoluble starch for storage
- used to produce fats or oils (lipids) for storage
- used to produce cellulose, which strengthens the cell wall
- used to produce amino acids for protein synthesis.
Explain why the glucose produced in photosynthesis can be used for respiration
The glucose produced in photosynthesis can be broken down to release energy in respiration which is used for cellular processes such as active transport
Explain the use of insoluble starch after it has been produced by glucose
The glucose produced in photosynthesis can be converted into the carbohydrate, starch and stored in the roots, leaves and cells.
These stores are used when photosynthesis isn’t happening e.g. at night or winter
The starch can be converted back to glucose by the plant when it is needed.
Why is it important that the starch used for storage is insoluble
Starch is insoluble which makes it much better for storing than glucose.
This is because a cell with lots of glucose in would draw in loads of water (by osmosis) and swell up.
Explain how the glucose produced in photosynthesis can used to produce fats or oils (lipids) for storage
The glucose produced in photosynthesis can be converted to fats or oils.
Fats and oils are used by the plant as a storage form of energy.
These are stored mainly in seeds and are used as a compact energy store
Explain why the glucose produced in photosynthesis can be used to produce cellulose
The glucose produced by photosynthesis is converted into cellulose which strengthens the cell wall
Explain why the glucose produced in photosynthesis can be used to produce amino acids
The glucose produced in photosynthesis is combined with nitrate ions (which plants absorb from the soil) to produce amino acids for protein synthesis.
When does photosynthesis only produce glucose
Photosynthesis only produces glucose during the day, when there is light
When do plant cells respire
Plant cells respire all the time including at night
What factors affect the rate of photosynthesis
Temperature
Light intensity
Carbon dioxide concentration
Amount of chlorophyll in the leaves
Describe and explain the trend in a light intensity/rate of photosynthesis graph
As light intensity increases, so does rate of photosynthesis, up to a certain point.
This indicates that light intensity is limiting factor.
However, after a certain point, an increase in light intensity has no effect on rate of photosynthesis …
… (the rate of photosynthesis no longer increases as light intensity increases) …
This indicates that light intensity is no longer limiting factor and something else probably is, such as: temperature or CO2 concentration
How do you know if a particular variable was a limiting factor
If we increase the light intensity, and the rate of photosynthesis increases, it shows that light intensity was the limiting factor (photosynthesis was not as fast as it could have been because there was not enough light)
