Unit 2 - Photosynthesis Flashcards
What is photosynthesis?
Photosynthesis is **a chemical reaction **which plants use to produce food
What is the word equation for photosynthesis?
light
Carbon dioxide + water → glucose + oygen
chlorophyll 
What do plants do during the day vs during the night?
In the day - **respiration **+ photosynthesis
At night - respiration
How do plants use light energy?
Using light energy, plants produce **glucose **from **carbon dioxide **and oxygen
Name the ways glucose is used by the plant? (3)
- Starch
- Cellulose
- Proteins/Fats
Use of glucose in plants - Starch?
- Plants store glucose as** starch **as energy for later
→Starch can be broken down into glucose as energy for later
Use of glucose in plants - Cellulose?
Cellulose is a structural compound
- Plants make cell walls out of cellulose
→It provides structure + strength
Why can’t glucose be turned into proteins directly?
Because glucose is made of carbon, hydrogen** **and oxygen and proteins contain nitrogen
Use of glucose in plants - Proteins/Fats?
Glucose can’t be turned into proteins directly
Other compounds (eg chlorophyll) contain magnesium
To build these compounds, the plant need more than glucose and it gets these from soil minerals
What are the 3 main factors that limit the rate of photosynthesis?
- CO2 concentration
- Light intensity
- Temperature
Why is CO2 concentration a limiting factor of photosynthesis?
It is a limiting factor because it is one of the reactants in the reaction
Explain what is happening on the graph for the limiting factor CO2 concentration
- Between points A and B: increasing the rate of CO2 concentration also increases the rate of photosynthesis until a certain point (B)
- Between B and C as the concentration of CO2 is increased, the rate of photosynthesis stays the same, this is because another factor has become limitng (eg light intensity/temperature)
Why is light intensity a limitng factor of photosynthesis?
Light intensity is a limiting factor of photosynthesis because photosynthesis is a photochemical reaction (aka is needs light energy)
Explain what is happening on the graph for the limting factor light intensity
- Between points A and B as the light energy increases, the rate of photosynthesi also increases. This is because there is **more energy avaliable for the reaction **
- Between B and C as light intesity increases the rate of photosynthesis stays the same because **another factor has become limitng **
Explain what is happening in the graph for the limitng factor temperature
- Between points A and B as the temperature increases the rate of photosynthesis also increases. This is because the reactants have more kinetic energy (more frequent collisions)
- Between points B and C as the temperature increases the rate of photosynthesis increases rapidly. The enzymes that control photosynthesis are denatured
