Navigate to resources by choosing units within one of the unit groups shown below.
Delivery guides are designed to represent a body of knowledge about teaching a particular topic and contain:
- Content: A clear outline of the content covered by the delivery guide
- Thinking Conceptually: Expert guidance on the key concepts involved, common difficulties students may have, approaches to teaching that can help students understand these concepts and how this topic links conceptually to other areas of the subject
- Thinking Contextually: A range of suggested teaching activities using a variety of themes so that different activities can be selected which best suit particular classes, learning styles or teaching approaches.
Content (from A-level)
|(a)||the interrelationship between the process of photosynthesis and respiration||To include the relationship between the raw materials and products of the two processes.
M0.1, M0.3, M0.4, M3.4
|(b)||the structure of a chloroplast and the sites of the two main stages of photosynthesis||The components of a chloroplast including outer membrane, lamellae, grana, thylakoid, stroma and DNA.|
|(c)||(i) the importance of photosynthetic pigments in photosynthesis
(ii) practical investigations using thin layer chromatography (TLC) to separate photosynthetic pigments
|To include reference to light harvesting systems and photosystems.
M0.1, M0.2, M1.1, M1.3, M2.2, M2.3, M2.4
|(d)||the light-dependent stage of photosynthesis||To include how energy from light is harvested and used to drive the production of chemicals which can be used as a source of energy for other metabolic processes (ATP and reduced NADP) with reference to electron carriers and cyclic and non-cyclic photophosphorylation
the role of water.
|(e)||the fixation of carbon dioxide and the light-independent stage of photosynthesis||To include how the products of the light-dependent stage are used in the light-independent stage (Calvin cycle) to produce triose phosphate (TP) with reference to ribulose bisphosphate (RuBP), ribulose bisphosphate carboxylase (RuBisCO) and glycerate 3-phosphate (GP) – no other biochemical detail is required.
|(f)||the uses of triose phosphate (TP)||To include the use of TP as a starting material for the synthesis of carbohydrates, lipids and amino acids
the recycling of TP to regenerate the supply of RuBP.
|(g)||(i) factors affecting photosynthesis
(ii) practical investigations into factors affecting the rate of photosynthesis.
|To include limiting factors in photosynthesis with reference to carbon dioxide concentration, light intensity and temperature, and the implications of water stress (stomatal closure)
the effect on the rate of photosynthesis, and on levels of GP, RuBP and TP, of changing carbon dioxide concentration, light intensity and temperature.
An opportunity to use sensors, data loggers and software to process data.
M0.1, M0.2, M0.3, M1.1, M1.3, M1.11, M3.1, M3.2, M3.4, M3.5, M3.6, M4.1
PAG4, PAG10, PAG11
HSW3, HSW4, HSW5, HSW12
Informative worksheets with colouring-in options.
Suggested resources from the contents list are ‘Chloroplasts and Mitochondria’, ‘Leaves’ and ‘Chemiosmosis in Chloroplasts’. Files download as Word documents.
Flashcard resource to learn 49 terms associated with photosynthesis.
The resource can be printed onto cards or used for various online games and quizzes. However the USA terms PGA and G3P are used for GP and TP.
Other versions of photosynthesis glossaries are available on the site, and these can be taken and customised by the teacher.
Experimental protocol, with teacher’s PowerPoint, technician’s details and illustrated student instructions and worksheet (questions and suggestions for further work) to download.
Minimal apparatus is required as the TLC strips can be suspended in boiling tubes from paperclips inserted into corks. The leaf extract is obtained by scraping grass leaves with a microscope slide, dissolving the juice in propanone, and using a hairdryer to evaporate the solvent to obtain a concentrated solution. Rf values can be calculated and compared.
Sample values for different pigments are given on the technician’s sheet, as is the supplier of the coated plastic TLC sheets.
M0.1, M0.2, M0.3, M1.1, M1.3, M2.2, M2.3, M2.4
Voiced animation describing light capture by chloroplasts, including details of chloroplast structure, pigment excitation, and the biochemistry of the light-independent reaction.
The description of chemiosmosis includes names of the complexes within the thylakoid membranes that are not required to be learnt.
For students used to using BBC Bitesize at GCSE, this is an archived Scottish Highers account of photosynthesis, including the fate of triose phosphate.
8 minute video providing an introduction to photosynthesis. It is organised into sections for ease of use in selecting relevant parts for class showing.
- Properties of Light
- Chloroplast Structure
- Light-dependent Reactions
- Calvin Cycle
The 3D computer generated graphics of the thylakoids and associated molecules are excellent and this resource is easy to use and well-worth showing. However be aware that the terms used for GP and TP are PGA and G3P, as is the case with the next video and other resources from the USA.
Hank Green summarises the importance and process of photosynthesis in this 13 minute video which contains colourful cartoon animations of the biochemistry of the light-dependent reaction and chemiosmosis.
Be aware that the term phosphoglycerate (also known as phosphoglyceric acid, PGA) is used instead of the syllabus term GP, and the term glyceraldehydes-3-phosphate (G3P) is used instead of the syllabus term triose phosphate (TP). Students will need to be warned of these name changes if this resource is used for revision, either in class or for private study.
(A video clip like this can be copied and embedded into a PowerPoint if YouTube is unavailable via your school network, though special software might be required).
Approaches to teaching the content
Photosynthesis can be treated with a top-down approach starting with gross primary productivity and relating the process to world food production and the base of food chains, or from a bottom-up perspective starting with the cell, chloroplast and biochemical detail. Experiments can come first to devise first principles about the factors necessary for and affecting the rate of photosynthesis, or can be used to reinforce theory. Experimental work can either use whole plants (e.g. Elodea in a photosynthometer) or plant parts (e.g. leaf discs) or cell free systems (e.g. Hill reaction) or manufactured units (e.g. immobilised algae balls).
Common misconceptions or difficulties students may have
The relationship with respiration needs to be carefully explained. Often students assume that plants photosynthesise and animals respire, so work on compensation points is helpful. Other distinctions to make clear are between photosystem II and photosystem I and between NADP (in photosynthesis) and NAD (in respiration). The similarity between chemiosmosis over thylakoid membranes and over the inner mitochondrial membrane should be made clear. There are various opportunities for graph work and, as always, students need to check the titles of axes carefully to be able to express the relationship between pairs of variables.
Conceptual links to other areas of the specification – useful ways to approach this topic to set students up for topics later in the course
The main areas of overlap and opportunities for synopticity are:
1.2.2 (g) Two opportunities for chromatography are described here.
2.1.1 (d) and (g) Plant tissues, cells and chloroplasts.
2.1.2 Polymerisation and the structure of monosaccharides, starch and cellulose can be revised when teaching photosynthesis. TLC of photopigments picks up on learning outcome (s).
2.1.4 Rubisco is estimated to be the world’s commonest enzyme. The effect of temperature on the rate of photosynthesis is due to the effect on Calvin cycle enzymes.
2.1.5 Thylakoid membranes are fine examples of very specialised versions of the basic fluid-mosaic phospholipid bilayer and proteins arrangement. Their impermeability to hydrogen ions for chemiosmosis can be stressed.
3.1.3 Leaf structure, transpiration to supply water as a raw material for photosynthesis and translocation of sucrose away from sources of carbohydrate are all important to an overview of photosynthesis within the context of the whole plant’s physiology.
4.1.1 (a) The effect of plant diseases in decreasing photosynthesis and therefore growth can be highlighted.
5.1.5 (b) The role of ABA in closing stomata in response to water stress results in availability of water acting indirectly to limit the rate of photosynthesis.
5.2.2 Similarities and differences between respiration and photosynthesis as discussed above.
6.2.1 In plant tissue culture the tiny plantlets are heterotrophic on their initial growth medium, not autotrophic as in the case of a normal photosynthesising plant. The technique of immobilising enzymes in alginate beads can be adapted to produce a model photosynthetic system for experimentation.
6.3.1 The energy transfer and carbon cycle sections pick up on an understanding of photosynthesis.
6.3.2 Sustainable management of ecosystems has to recognise the primacy of photosynthesis as providing the energy for all other trophic levels.
Information about the relationship between photosynthesis and respiration, including graphs presented as ‘transparency masters’ for teaching the concept of compensation points over a day or as light intensity or carbon dioxide concentration increase. Resource is from the Canadian TomatosphereTM organisation that teaches about tomato plant biology in the context of space exploration.
Analysis of graphed data could utilise maths skills such as M0.1, M3.4, M3.5, M3.6
This provides a practical protocol for the Hill Reaction to investigate the light-dependent reaction of photosynthesis.
A centrifuge is required to separate a pellet of chloroplasts from other cell debris from a homogenate of spinach leaves in buffer. When carrying out the practical concepts to stress are the experimental details which preserve the biochemical activity of the isolated chloroplasts and the role of DCPIP in replacing NADP at the end of non-cyclic photophosphorylation.
Two downloadable documents on the Hill Reaction, a student and a teacher sheet, are available from the OCR website under ‘teaching resources’ at the foot of the page.
The basic Hill Reaction protocol can be adapted as described in this practical examination, if the past paper can be accessed in school. It is no longer available via the OCR website, though copies of the mark scheme with sample results and graph are available on the net via third parties.
Capillary tubes containing the chloroplast suspension mixed with DCPIP are placed on a white tile under a bench lamp. These can be compared to a capillary tube containing chloroplast suspension only as a colour standard. Coloured filter ‘tents’ can be placed over the capillary tubes to test the effect of light wavelength on the rate (time taken for colour to change to match colour standard) of the light-dependent reaction. If the light wavelength corresponding to each colour of filter is known, the results can be graphed.
The capillary tube technique could also be used to investigate light intensity by varying the distance of the bench lamp. The advantage of using tiny quantities of reagents in capillary tubes is the time taken for decolorisation of DCPIP is short.
This conceptual overview explores different approaches to measuring photosynthesis, with links to some of the experimental protocols listed in ‘Thinking Contextually’ below, as well as to work with water plants such as Elodea and Cabomba.
Using these in syringes attached to capillary tubes can give data on oxygen evolution in a short time and allow calculations of volume of gas from distance X cross-sectional area and rate calculations from graphs if light intensity or concentration of hydrogen carbonate in the water is varied.
M.0.1, M.1.1, M1.2, M.3.2, M.3.5, M.4.1
Practical instructions for an investigation into sun and shade plants using leaf discs (measuring time taken for discs to float due to oxygen evolution).
Links to other supporting information for work with leaf discs are given.
Relevant to learning outcome (b), this links synoptically with sections 6.1.2 and 6.1.3 and provides a plant-based practical using the principles of chromatography (gel electrophoresis). It could be used as a follow-up to the basic TLC process referenced in the first section, to show how the technique has been developed.
A kit is available from NCBE to support this activity.
PCR can be carried out in three water baths maintained at 55°C, 72°C and 94°C, avoiding the need for a thermal cycling machine.
Immobilising algae in alginate balls provides a relatively new experimental context for investigating photosynthesis. The balls are fun to make, easy to handle and if made the same size constitute a fixed ‘unit’ of photosynthesis for comparing across different values of an independent variable. Instructions for SAPS are provided, with ideas for experiments, and ordering details for a kit from their partner in developing the protocol, NCBE at the University of Reading. The importance of phytoplankton algae as the base of marine food chains is easy to introduce in the context of this work.
Three resources below deal with the phenomenon of chlorophyll molecules emitting fluorescence when excited electrons fall back to base state, two with a lab demonstration of this and the third with the use by NASA of imaging equipment to measure world vegetation from space.
Photosynthetic animals (corals, sea slugs) provide an opportunity to consider symbiosis, to reconsider how chloroplasts got into eukaryotic cells, and in the case of Elysia chlorotica, how genes may be transferred horizontally between species of different kingdoms.
The rate of photosynthesis is placed within a food-growing context with reference to ministry of agriculture guidelines for greenhouse growing in Canada and growing strawberries under cover in Ireland.
This page provides an informative introductory video clip showing the technique for immobilising the alga Scenedesmus quadricauda in alginate balls and students at work using algae balls to investigate the effect of light intensity and light wavelength.
Follow the link for post-16 resources for teachers’ notes and student hand outs, information of the National Centre for Biotechnology Education kit, obtaining filters to alter light wavelength and a sample colour standard print-out matching pH to different colours of hydrogen carbonate indicator solution to interpret the results.
With known light wavelengths and dependent variable pHs or related concentrations of carbon dioxide, results can be graphed.
NCBE site with details of algae balls photosynthesis kit described above for ordering materials.
Experiment instructions for seeing fluorescence from a chlorophyll extract.
Ideally the extract should be illuminated strongly first and then be viewed with a source of ultraviolet (‘black’) light in the dark.
Video just over a minute long to show the fluorescent glow from chlorophyll, as described in the RSC resource (see Activity - The solar spark: Chlorophyll fluorescence).
Article and 3 minute video clip showing how fluorescence released by chlorophyll can be detected by satellites in space in order to produce maps of world vegetation and its health.
Introduction to symbiotic algae which live in the tissues of animals such as sea slugs and corals. Students frequently wonder if photosynthesis would be a desirable attribute for animals or even humans. This page and related links explore photosynthesis using symbionts in animals.
Article and short video clip describing a sea slug which steals chloroplasts from the algae it eats and possesses a key gene required for photosynthesis in its nuclear genome.
Corals and sea slugs possessing symbiotic algae are common (see previous resource) but in this case an animal has ‘stolen’ a key gene needed for photosynthetic metabolism in its own cells.
This technical fact sheet for growers of greenhouse crops could be used as the basis for an exploration of the applications of knowing how carbon dioxide concentration affects the rate of photosynthesis and therefore plant growth.
It could be linked to questions of marketing, prices for early and mid-season vegetables and horticultural produce, and overall yield. Linking this to a specific popular crop grown under glass or polythene in the UK, such as strawberries, would increase student interest.
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