Photosynthesis TOPIC 4 Flashcards
What are the specialised features of a leaf
- waxy cuticle
- transparent upper epidermis
- packed palisade mesophyll
- lots of chloroplasts
- airy spongy mesophyll
- xylem
- phloem
- lower epidermis
- air spaces
- stomata
- gurad cells
What is photosynthesis
a series of endothermic chemical reactions which occur in plant cells which contain chloroplasts to generate energy
When is repiration carried out
all the time - day and night
What is the word equation for photosynthesis
carbon dioxide + water -> glucose + oxygen
what is the chemical equation for photosynthesis
6 CO2 + 6 H2O -> C6H12O6 + 6 O2
What are the factors which are required for photosynthesis to occur
- light
- warmth
- chlorophyll
what is the waste product of photosynthesis
oxygen
How do plants get carbon dioxide
CO2 diffuses down the concertration gradient from the air in the environment through the stomata into the air spaces in the leaf
How do plants get water
Water moves by osmosis down the water potential gradient from the sapces between soil particles into the root hair cell
Describe the method to test leaves for startch
- set up water bath using a beaker, tripod, gauze and bunsen burner
- use forceps to put leaf in boiling water
- turn off bunsen
- fill boiling tube 1/3rd with ethanol
- place in beaker for 10min
- remove leaf from ethanol with forceps
- dip leaf in hot water
- smooth out leaf onto white tile
- add iodine solution
- observe colour change
Why do we use ethanol when testing leaves for startch
the ethanol removes the chlorophyll from the leaf so it changes colour with the iodine easier
why do we boil the leaf when testing it for startch
to remove the waxy cuticle
What are the limiting factors
- light intensity
- carbon dioxide concertration
- temperature
- chlorophyll levels in leaf
How is light intensity a limiting factor
plenty of light = lots of phtotsynthesis
it is a limiting factor until it plateaus
How is CO2 concertration a limiting factor
more CO2 = more photosynthesis
- CO2 levels rise at night and get used up in the morning
it is a limiting factor until it plateaus
Why is the more CO2 at night
because the plants respire but don’t photosynthesise
How much of the atmosphere is CO2
0.04%
How can CO2 levels be overcome
Science labs or greenhouses can aartificially increase the levels of CO2
How is temperature a limiting factor
hgiher temperature = faster/more photosynthesis
temperture increase generates more kinetic energy
What can happen to the plant if temperature gets too high
- enzymes denature around 40-50 celcius
- photosynthesis is controlled by enzymes
How is chlorophyll a limiting factor
Chlorophyll absorbs the light which develops photosynthesis
If a plant doen’t mave enough minerals (magnesium) it will die because it cannot grow
What do plants use the glucose from photosynthesis for
- respiration
- converted into insoluable startch
- produce lipids or oils
- produce cellulose
- produce amino acids
why do plants convert glucose to cellulose
to stengthen the cell wall
why do plants convert glucose to startch
- it is insoluable ~ doen’t affect osmosis
- provides an energy store when it is too dark
- produce tubers and bulbs to help survive through the winter
