Photosynthesis Flashcards
Where does photosynthesis happen in the leaf?
chloroplast
Photosynthesis is an endothermic reaction. What does this mean?
absorbs light energy from the sun
What is the word equation for photosynthesis?
carbon dioxide + water -> glucose + oxygen
What is the chemical equation for photosynthesis?
How do you destartch a leaf?
Placing them in the dark for 48 hours
What are the 5 steps to test a leaf for starch?
- Destarch the plant
- Boil the leaf in water
- Leaf placed in ethanol
- Lead placed in warm water
- Iodine dropped in leaf
Why do you destarch a leaf?
To enusre any starch made was created during the experiment
Why do you boil the leaf in water when testing for starch?
Killing the leave and stops further reactions
Why do you place the leaf in ethanol when testing for starch?
Removes the chlorophyll (green colour) so decolourises the leaf
What is one safety precaution when placing the leaf in ethanol?
Bunsen burner must be turned off as ethanol is HIGHLY flammable
Why do you place the leaf back in warm water when testing for starch?
Softens the leaf (less brittle) so it can be spread out
What is the colour change for iodine if the leaf tests positive for starch?
yellow/brown to blue/black
Some leaves are green where chlorplast are present and white where they are not. What are these leaves called?
Variegated
How would you test if carbon dioxide is needed for photosynthesis?
Use two conical flasks with similar photosynthesising plants in each. This ensures that no carbon dioxide enters the atmosphere surrounding the plants. Place soda lime (sodium hydroxide) in one flask to absorb carbon dioxide but not in the other (acts as a control flask to which the other can be compared).
What is the function of the waxy cuticle?
Thin and transparent physical defence- allows light through. Waterproof layer that reduces water loss by evaporation.
What is the function of the upper epidermis?
Lacks chloroplasts and so allows light to reach the mesophyll cells
What is the function of the pallisade mesophyll?
-Regular structured cells that are closely packed together which increase the surface area for light absorption.
-They contain a high concentration of chloroplasts and hence chlorophyll for maximum light absorption for photosynthesis.
What is the function of the spongy mesophyll?
-Contain inter-cellular air spaces for gaseous exchange (allows carbon dioxide to enter and oxygen to leave the photosynthesising cells in the palisade mesophyll)
-Cells have a large surface area and moist walls which enhance diffusion of gases
What is the function of the guard cells?
Control the opening and closing of stomata and therefore regulate gaseous exchange.
What is the function of the stomata?
Pores on the underside of the leaf which allow gases to diffuse. Stomata are open during the day and close at night –to control the evaporation of water
Define limiting factor
If any of the raw materials needed for photosynthesis are in short supply then the rate of photosynthesis will slow down – this is the limiting factor
What are the three limiting factors?
Light, carbon dioxide and tmeperature
What chemical can be used to determine the amount of carbon dioxide in the air?
hydrogen carbonate indicator
What conditions would hydrogen carbonate indicator be purple?
decrease in carbon dioxide
(photosynthesis is greater then respiration)
What conditions would hydrogen carbonate indicator be red?
rate of photosynthesis is equal to the rate of respiration. There is no net gas exchange. This is the compensation point
(dawn and dusk)
What conditions would hydrogen carbonate indicator be yellow?
Respiration greater than photosynthesis
increases carbon dioxide levels
