Chapter 2 - Photosynthesis Flashcards
Where does PS take place in the plants?
The green parts (chlorophyll is present)
What does chlorophyll do during PS ?
Traps the energy from the suns light.
Is photosynthesis exo/endothermic ?
endothermic
What is the waste product produced by PS?
oxygen
What is the word equation for PS?
light energy
carbon dioxide + water——————->glucose + oxygen
chlorophyll
What is the balanced symbol equation for PS?
6CO(2) +6H(2)O —–> C(6)H(12)O(6) +6O(2)
Give three uses for glucose in a plant.
1: Respiration
2: Storage - many plants convert it into starch and oils for storage
3:Useful substances - glucose can be turned into cellulose, chlorophyll and protein.
List the steps taken to carry out the starch test for a leaf.
1: Place leaf in boiling water for 30 seconds
2: Place leaf in boiling ethanol (to remove the chlorophyll)
3: then place back into water to stop leaf drying out.
4: Place on white tile and add iodine
If starch is present it will go from yellow-brown to blue-black.
Why and how do you destarch a plant ?
Leave in a dark cupboard for 2 days. Starch already in the leaf will be used up before you carry out the experiment.
How do you show light and chlorophyll is needed in PS?
1: Destarch the plant
2;Test the leaf for starch (if negative continue)
3:Cover one part of the leaf with foil
4:Place the plant in bright light for several hours
5:Test leaf for starch. Make drawing of leaf after the test.
How do you show carbon dioxide is needed for PS?
Get one leaf from a plant and place it in a conical flask with water in it. Get another leaf and place it in one with sodium hydroxide (removes CO2 from the plant). Test both leaves for starch and the one in water should test positive while the one in sodium hydroxide should test negative.
How will changing the light intensity change the rate of PS?
The higher the light intensity the higher the rate of PS.
What are the factors affecting PS?
Carbon dioxide availability
Light intensity
Water
Temperature
What is the term used to describe the best level for the reaction ?
Optimum level
If one factor of PS is in short supply it is known as …….
a limiting factor ( the rate of PS is determined by the factor that is in the shortest supply)
What two processes are leaves adapted for ?
Light absorption
Gas exchange
What is a mesophytic leaf?
a typical unspecialised leaf
How is a leaf adapted for light absorption?
- short distance between upper and lower surfaces.
- large surface area
- thin transparent cuticle, reduces water loss while letting light to enter into the leaf
- epidermis lacks chloroplasts to allow light in.
- many chloroplasts rich in chlorphyll
- regular structure of the palisade mesophyll, allows many cells rich in chloroplasts to be near the surface of the cell.
How is a mesophytic leaf adapted for gas exchange ?
- the intercellular air spaces in the spongy mesophyll allow CO2 in and O2 out.
- stomata, which allow gases to enter and leave the leaf. Each stomata is surrounded by two guard cells that regulate the opening and closing of the stoma.
What is need and what is the waste product for plant respiration ?
O2 is needed and CO2 is produced as a waste product.
Explain what happens at night regarding the movement of gasses in a leaf.
At night there is no light for photosynthesis so only respiration occurs. Therefore O2 will enter the leaf and CO2 will leave.
Explain what happens in the day regarding the movement of gasses in a leaf.
Both processes will take place. When light intensity is high the level of PS exceeds the level of respiration so CO2 enters the leaf and O2 exits the leaf.
What is known by the term compensation point ?
There will be times during the day when the light intensity is low. This causes PS to occur very slowly. At these points , usually dawn and dusk the rates of Ps and respiration are equal and there will be no overall or net gas exchange.
Describe the colour change of hydrogencarbonate indicator.
bright red - normal conc
yellow - increased conc
purple - lowered conc
