Photosynthesis 2.9

Photosynthesis is introduced in this topic. The main new idea is that the process is not a single step reaction but a sequence of reactions which occur in different parts of the chloroplast. The photosynthetic pigments are attached to membranes and the enzymes for the light independent reactions are found in the liquid stroma.


Key words

Learn and test your biological vocabulary for 2.9 Photosynthesiusing these flashards 

Clean sweep - quick revision through the whole topic

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - good revision for all students.

Read the slides and look up any words or details you find difficult to understand.

Video tutorial

A short video tutorial is planned here.

Revision summary list for topic 2.9 Photosynthesis

  • Photosynthesis uses light energy to produce carbon compounds in cells.
  • Visible light ranges from violet (400nm) the shortest wavelength to red (700nm) the longest.
    (Students are not expected to recall the wavelengths of other colours.)
  • Absorption specrum shows - red and blue light absorbed most and green light least (it is reflected).
  • Photolysis of water produces oxygen
    (and also ATP & NADPH)
  • Energy ( from photolysis) is needed to produce carbohydrates and other carbon compounds from carbon dioxide.
  • Limiting factors of photosynthesis can be; Temperature, light intensity and carbon dioxide concentration.

Skills (can you ....)

  • Understand that photosynthesis have caused changes to the Earth’s atmosphere, oceans and rock deposition.
  • Learn how to draw
    • an absorption spectrum for chlorophyll and
    • an action spectrum for photosynthesis.
  • Design experiments to investigate the effect of limiting factors on photosynthesis.
    Ref: control of variables is essential.
  • Separate photosynthetic pigments by chromatography. (Practical 4) either by paper chromatography or thin layer chromatography (gives better results)

Revision mind map

This diagram summaries the main sections of topic 2.9
Test if you can draw something like these concept maps from memory.

Review questions

This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding.

1

Whiich pigments in plants abosorb light and where are they found?

Red and blue light is absorbed by chlorophyll, but very little of the green light.
Chlorophyll is attached to the inner membranes of the chloroplasts of plant cells.

2

What is the source of energy used by the organelle shown in the image below?

Photosynthesis uses light energy to produce carbon compounds in the chloroplasts of cells.

3

Which of the following best describes violet light.

Visible light ranges from violet (400nm) to red (700nm) the longest wavelength.

There are peaks in the absorption spectrum of chlorophyll at red and blue light.

Violet light is absorbed by chlorophyll
(Students are not expected to recall the wavelengths of colours except red and violet.)

4

Whiich of the following points best describes the absorption spectrum graph below?

Absorption spectrum shows the amounts of each wavelength of light - red and blue light absorbed most and green light least (it is reflected).

5

What is the name of the reactions of photosynthesis which produce oxygen ATP and NADPH?

Photolysis of water in the light independent reactions produces oxygen ATP & NADPH

6

The chloroplast needs two things from the light dependent reactions for it's light independant reactions which makecarbohydrates. What are they?

Energy ( from photolysis) is needed to produce carbohydrates and other carbon compounds from carbon dioxide

Hydrogen is also needed carried by reduced NADP - NADPH.

7

The rate of photosynthesis is usually prevented from increasing by a single factor.

What is the name given to this factor?

Limiting factors of photosynthesis can be; Temperature, light intensity and carbon dioxide concentration.

8

The graph below shows data about the carbon dioxide concentration of the earth's atmosphere over the last 300 million years

Which of the following best explains why these changes occur?

Understand that photosynthesis have caused changes to the Earth’s atmosphere, oceans and rock deposition.

Every summer photosynthesis reduces the carbon dioxide concentration of the atmosphere.

9

This apparatus below has been set up by a student to investigate photosynthesis.

They want to find out if the size of flask affects the rate of photosynthesis.
The three fasks are 250ml, 500ml and 1000ml volume.

Which factors need to be controlled so that the results can be compared to each other?

In this experiment the size of plants, and the temperature, light intensity will need to be controlled.

Size of the flask is the independant variable and the concentration of carbon dioxide is the dependent variable, used to measure photosynthesis rate.

10

By what method do biologists separate photosynthetic pigments extracted from plants?
What is the name of this separation technique?

Separate photosynthetic pigments by chromatography. (Practical 4)
either by paper chromatography or thin layer chromatography (gives better results)

Total Score:

Revision fun activity

Everyone needs a little bit of light relief after revising hard. This is a set of fun, retro, arcade games which actually continue to help revision of topic 2.9 Photosynthesis.

If you can't see the content below, please click this link to Photosynthesis arcade games