B1.4 Photosynthesis Flashcards
What is photosynthesis?
Photosynthesis is a chemical reaction in which producers make food by carbon dioxide reacting with water in the presence of sunlight to form glucose and oxygen
How do plants take in carbon dioxide?
It comes from the air, and then diffuses into the plant through the stomata(tiny pores in the underside of leaves)
How do plants take in water?
Water enters the roots through root hair cells by osmosis, from the soil
What is the oxygen produced in photosynthesis used for?
Some is used for respiration, the rest is waste product, so it is released back into the environment
Where does photosynthesis occur?
Photosynthesis takes place in the chloroplast, so mainly in The leaves
Why does photosynthesis occur in the chloroplasts
Because light transfers the energy from the sun to chlorophyll in the chloroplasts , and light energy is needed in the reaction to make glucose
Why are leaves and stems green?
Because the contain the green pigment chlorophyll in their chloroplasts
What is the first stage of photosynthesis?
Light dependent stage is when energy transferred form light splits water molecules into oxygen and hydrogen ions
What is the second stage of photosynthesis?
Carbon dioxide gas combines with hydrogen ions to make glucose
What kind of reaction is photosynthesis ?
It is an example of an endothermic reaction, this means that energy must be transferred from the surroundings to keep it going.
It absorbs sun light
What is a phototropism?
Growing towards the light
What is a photometer ?
An instrument for measuring light intensity
Photoconductive =
A material whose resistance decreases when it absorbs light
What happens to glucose produced?
- when it’s not needed straight away it is converted into starch (store of energy)
- converted into sucrose and fructose
-cellulose to form cell walls
-plus nitrogen,
proteins for growth+ repair
and fats and oils(food store and growth)
What are the steps to test for starch in a leaf?
- place leaf in boiling water to kill it
- then place it in a boiling tube of boiling ethanol to remove the chlorophyll (so you can see colour change )
- add a few drops of iodine solution
What colour does the iodine solution Turn if starch is present?
Blue/black
Formula
Carbon dioxide+ water —> glucose+ oxygen
6Co2 + 6H20 —-> C6h12O6 +6O2
Prove carbon dioxide needed for photosynthesis
Destarched plant and place inside polythene bag,
Add pot of soda lime (absorbs CO2 and water vapour)
Seal bag
Place in sunlight before testing leaves for starch
How to prove sunlight needed for photosynthesis
Destarched plant and cover one of leaves w black card/ tin foil
Place in sun for hours and test for presence of starch in leaf
Prove oxygen given off during photosynthesis
Place upturned test tube above aquatic plant (pondweed)
Put apparatus in sunlight
Collected tube full of gas glowing splint test
Limiting factors affecting rate of photosynthesis
Light intensity, carbon dioxide, temperature
How does light intensity effect rate of photosynthesis
Higher light intensity, faster rate of photosynthesis
Until reaches maximum rate
Carbon dioxide
Greater concentration of carbon dioxide, faster rate of reaction
Until reaches maximum rate of reaction
Most common limiting factor due to atmosphere 0.04%
Temperature
Higher temperature, faster reaction as enzyme controlled reaction
Temp too high = enzymes denature and reaction stops
How to measure rate of photosynthesis
Elodea/pondweed count number of oxygen bubbles produced per minute
Inverse square law
Double distance from light source, light intensity falls by factor 4
Relative light intensity= 1/distance from light source^2
