Essential idea: Light energy is converted into chemical energy.
The images above show Photosystem II and Photosystem I. These protein complexes contain a number of chlorophyll and other pigments which allow them to absorb light energy. The photosystems use light energy to excite electrons and split water molecules freeing hydrogen ions (Photosystem II only). These two process provide the energy and some of the key ingredients required to produce glucose.
Understandings, applications and skills
|8.3.U1||Light-dependent reactions take place in the intermembrane space of the thylakoids.|
|8.3.U2||Light-independent reactions take place in the stroma.|
|8.3.U3||Reduced NADP and ATP are produced in the light-dependent reactions.|
|8.3.U4||Absorption of light by photosystems generates excited electrons.|
|8.3.U5||Photolysis of water generates electrons for use in the light-dependent reactions.|
|8.3.U6||Transfer of excited electrons occurs between carriers in thylakoid membranes.|
|8.3.U7||Excited electrons from Photosystem II are used to contribute to generate a proton gradient.|
|8.3.U8||ATP synthase in thylakoids generates ATP using the proton gradient.|
|8.3.U9||Excited electrons from Photosystem I are used to reduce NADP.|
|8.3.U10||In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate.|
|8.3.U11||Glycerate 3-phosphate is reduced to triose phosphate using reduced NADP and ATP.|
|8.3.U12||Triose phosphate is used to regenerate RuBP and produce carbohydrates.|
|8.3.U13||Ribulose bisphosphate is reformed using ATP.|
|8.3.U14||The structure of the chloroplast is adapted to its function in photosynthesis.|
|8.3.A1||Calvin’s experiment to elucidate the carboxylation of RuBP.|
|8.3.S1||Annotation of a diagram to indicate the adaptations of a chloroplast to its function.|
[Text in square brackets indicates guidance notes]
Two fun musical introductions from Mr W on the light and light independent reactions of photosynthesis.
Presentation and notes
The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.
Meet the membrane - party with the Thylakoids
Once students are familiar with the light dependent reactions. They can play 'meet the membrane'. One student is a party host who greets arrivals. The other students play the part of structures or molecules involved in the light dependent reactions. Choose from:
Extension: once molecules and structures can easily be identified the game can be made more by giving each student a list of key terms they cannot use when introducing themselves.
Can you complete this crossword puzzle (thanks to L Stanley) on photosynthesis?
The busy leaf by FTExploring is a good introduction and nicely links structure of the leaf to function
Photosynthesis by the University of Illinois (lecture notes and nice diagrams)
Photosynthesis by Interactive concepts in biochemistry
Photosynthesis by National Louis University (lecture notes)
Photosynthesis by McGraw and Hill (great narrated animation)
Light Dependent reactions
Harvesting light by Sunamas Inc.
An animation of the light dependent reactions by Mr Brown (not annotated - possible student activity)
Light reactions in photosynthesis by Smith University
Light reactions by John Kyrk
Photosynthesis - light dependent reactions by St Olaf College
Visualisation of Photosynthesis from NDVirtualCell
Photosynthesis: light reactions by Khan Academy
Photosynthesis: light reactions and photophosphorylation by Khan Academy
Photosynthesis electron transport and ATP synthesis by McGraw and Hill (relates cell structures to function)
Light Independent reactions
Carbon fixation in photosynthesis by Smith University
Biosynthetic reactions by John Kyrk
Photosynthesis: Calvin cycle by Khan Academy
Calvin cycle by McGraw and Hill
Nature's smallest factory: the Calvin cycle by TED ed
Nature of science
Developments in scientific research follow improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation. (1.8) [linked to 8.3.A1 - details in the presentation]
Theory of knowledge
The lollipop experiment used to work out the biochemical details of the Calvin cycle shows considerable creativity. To what extent is the creation of an elegant protocol similar to the creation of a work of art?