Limiting factors
What can affect the rate of photosynthesis?
Less light = plant photosynthesises slowlyEven if there is a lot of
water and carbon dioxide
More light = faster photosynthesis
Less carbon dioxide = slower photosynthesisEven if there is a high
light intensity
More carbon dioxide = faster photosynthesis
Too cold/too hot = slower
photosynthesisEven if other variables
are there
Optimum temperature = faster photosynthesis
Limiting factorsWhat can slow the rate of photosynthesis?
Light Intensity
Graph:
Description:
Carbon dioxide
Graph:
Description:
Temperature
Graph:
Description:
What does the plant do it for?
Glucose:- Used in respiration and growth - Stored as starch (insoluble)
Oxygen: - By product (waste)- Let back out into atmosphere
Glucose
1. Energy2. Cellulose in cell walls3. New chlorophyll
Stored as starch as it is insoluble
TUBER
Create a story board to explain the journey from carbon dioxide to a chip
State the word equation for
photosynthesis
Describe the limiting factors
of photosynthesis
Explain how plants use the glucose they produce in
photosynthesis
Your Task
Over the Christmas holidays create an exploration for the following experiment:
- Investigate limiting factors on photosynthesisChoose one of the three we have learnt aboutUse the exploration criteria to complete this, also look at the exploration you completed for enzymes – how could you improve?
Due: Tuesday 6th January
Make sure you also revise for your SAW test
2.9 Photosynthesis
Understanding:- Photosynthesis is the production of carbon
compounds in cells using light energy- Visible light has a range of wavelengths
with violet the shortest wavelength and red the longest
- Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours
- Oxygen is produced in photosynthesis from photolysis of water
- Energy is needed to produce carbohydrates and other carbon compounds
- Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis
Applications:- Changes to the Earth’s atmosphere,
oceans and rock deposition due to photosynthesis
Skills:- Design of experiments to investigate
limiting factors on photosynthesis- Separation of photosynthetic
pigments by chromatography- Drawing an absorption spectrum for
chlorophyll and an action spectrum for photosynthesis
Nature of science:- Experimental design: controlling
relevant variables in photosynthesis experiments is essential
Photosynthesis
Plants are able to make their own energy using sunlight and simple
carbon compounds.
Carbon dioxide + water glucose + oxygen
Energy converts from light energy to chemical energy
Wavelengths of light
Too short to see: X-rays, UV rays
Too long to see: Infrared
Visible light range from 400 to 700 nanometres
Photosynthesis
Wavelengths of light detected by human eye also used in photosynthesis
They are the most abundant wavelengths on earth so plants have adapted to use these
Pigments
Pigments are substances that absorb light – therefore appear coloured to us
If a pigment absorbs all colours, it appears black as it emits no light
Some pigments only absorb certain wavelengths of light
Pigments
Gentian flower absorbs all colour except blue
So it appears blue
This part of sunlight is reflected and can pass into our eye.
Chlorophyll
There are various forms of chlorophyll but they all appear green to us
They absorb red and blue light
Green light is absorbed less effectively so is reflected
This is why plants look green!
Spectra
ActionShows rate of photosynthesis at each wavelength of
light
AbsorptionPercentage of light absorbed at each wavelength of
each pigment
Rules to draw spectra
Action Absorption BothY-axis should be used
for rate of photosynthesis – often given as a
percentage of the maximum rate (0-
100%)
Y-axis should be labelled % absorption
(0-100%)
Horizontal axis should have label:
wavelength (nm)
Scale from 400-700 nm for wavelength
Separating Photosynthetic pigments
Chloroplasts have many types of chlorophyll and other accessory pigments
Because they absorb different wavelengths of light they look different colours to us
We can separate these pigments by chromatography
Separating Photosynthetic pigments
A spot containing leaf pigments is placed near one end of the strip of chromatography paper
A solvent is allowed to run up the strip
This separates out the different types of pigment – your experiment on Tuesday
Exploration
Finish exploration ready to hand in (hard copy) tomorrow in the lesson
If you have already finished this – revise for your SAW exam
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