This extensive and fully-resourced lesson describes the principles and explains the techniques used in the production of recombinant DNA in genetic engineering. Both the engaging PowerPoint and accompanying resources have been written to cover points 6.1.3 (f) (i & ii) of the OCR A-level Biology A specification. The lesson begins with a definition of genetic engineering and recombinant DNA to allow students to begin to understand how this process involves the transfer of DNA fragments from one species to another. Links are made to the genetic code and transcription and translation mechanisms, which were met in module 2, in order to explain how the transferred gene can be translated in the transgenic organism. Moving forwards, the method involving reverse transcriptase and DNA polymerase is introduced and their knowledge of the structure of the polynucleotides and the roles of enzymes is challenged through questions and discussion points. Restriction enzymes are then introduced and time is taken to look at the structure of a restriction site as well as the production of sticky ends due to the staggered cut on the DNA. A series of exam-style questions with displayed mark schemes are used to allow the students to assess their current understanding. The second half of the lesson looks at the culture of transformed host cells as an in vivo method to amplify DNA fragments. Students will learn that bacterial cells are the most commonly transformed cells so the next task challenges their recall of the structures of these cells so that plasmid DNA can be examined from that point onwards. The following key steps are described and explained: • Remove and prepare the plasmid to act as a vector • Insert the DNA fragment into the vector • Transfer the recombinant plasmid into the host cell • Identify the cells which have taken up the recombinant plasmid • Allow the transformed host cells to replicate and express the novel gene Time is taken to explore the finer details of each step such as the addition of the promoter and terminator regions, use of the same restriction enzyme to cut the plasmid as was used to cut the gene and the different types of marker genes. As well as understanding and prior knowledge checks, quick quiz competitions are used throughout the lesson to introduce key terms such as cDNA and EcoR1 in a memorable way.

This lesson describes the importance of homeostasis in mammals and focuses on the parts of a control system and negative feedback . The detailed and engaging PowerPoint and accompanying resources have been designed to cover the content of points (1 and 2) of topic 14.1 of the CIE A-level biology specification, but positive feedback is also discussed to broaden student understanding. As homeostasis is a topic met at GCSE, this lesson has been written to build on this knowledge as well as to check on their prior knowledge of earlier A-level topics such as osmosis when considering blood water potential and the use of glucose as a respiratory substrate. Discussion points are written into the lesson at regular intervals to encourage the students to consider why a particular process or method takes place and understanding checks allow them to assess their progress. Students will recall how body temperature, blood water potential and blood glucose concentration are maintained within restricted limits and the importance of these systems are looked into in detail. Time is taken to consider the importance of maintaining these aspects, specifically with relation to the activity of enzymes. As such, students will also discuss how the pH of the blood is maintained. The key components of the control system are recalled and then time is taken to focus on the cell signalling that occurs between the coordination centre and the effectors. Students will learn to associate the response with either the use of the nervous or endocrine system. The final part of the lesson looks at the importance of negative feedback in reversing the change in order to bring the aspect back to the optimum and the added degree of control which this provides. Positive feedback is also briefly mentioned at the end.

This lesson describes the homeostatic control of blood glucose concentration using negative feedback mechanisms. The PowerPoint and accompanying resources have been planned to cover the content of points (9 and 10) of topic 14.1 of the CIE A-level Biology specification (for assessment in 2025-27) and therefore also explain how the binding of glucagon and the formation of a second messenger is cell signalling. The wide range of activities will maintain motivation and engagement whilst the content is covered in detail to enable the students to explain how the receptors in the pancreas detect the concentration change and how the hormones attaching to receptor sites on the liver triggers a series of events in this effector organ. This is a topic which has a huge amount of difficult terminology so time is taken to look at all of the key words, especially those which begin with the letter G so students are able to use them accurately in the correct context. The final part of the lesson looks at the role of the secondary messenger, cyclic AMP, and describes how this is involved when glucagon and adrenaline attach to receptors on the liver. The action of adrenaline is also considered and linked to the breakdown of glycogen to glucose during glycogenolysis.

This fully-resourced lesson describes how Mycobacterium tuberculosis and Human Immunodeficiency virus infect human cells. The PowerPoint and accompanying resources have been designed to cover point 6.6 of the Pearson Edexcel A-level Biology A (Salters Nuffield) specification and ties in directly with the previous lesson where the structure of bacteria and viruses were compared. The lesson begins by ensuring that students recognise that TB is caused by the infection of a species of bacteria known as Mycobacterium tuberculosis and they will challenged to use their knowledge of scientific classification to recall that this pathogen is found in the mycobacteria genus. At this point, the students are told that the cell walls of this genus contain mycolic acids and later in the lesson they will have to work out that this specialist feature enables this pathogen to survive phagocytosis. A series of exam-style questions will challenge their knowledge of the respiratory and immune systems as they can understand how the bacterium travels to the alveoli where it is engulfed by a macrophage. Key terms like granuloma and necrosis are introduced and the sequence of events that occur following the formation of this aggregate of cells is described. The structure of viruses was covered during the previous lesson, so this next part of the lesson starts by challenging the students to recall the capsid, genetic material in the form of viral RNA and the lipid envelope. At this point, the students are introduced to gp120, the glycoprotein which is exposed on the surface of the lipid envelope, as this structure is critical for the entry of the virus into host cells. Students will annotate a basic diagram of HIV with these four structures which also has gp41 labelled. A quick quiz competition introduces the names of the enzymes found inside the capsid Moving forwards, the main task of this part of the lesson describes how HIV binds to the helper T cells, injects its capsid and integrates its DNA into the host’s genome in order to replicate to form virus particles (virions). Students are guided through the formation of a detailed answer about the mechanism of HIV and have to input key terms and structures where information is missing. Students will learn that the increase in the number of virus particles and a decrease in helper T cells and other immune cells results in infections like TB and by opportunistic pathogens and that this stage is recognised as AIDS

This lesson evaluates the methods used by zoos and seed banks in the conservation of endangered species. The PowerPoint and accompanying resources have been primarily designed to cover point 4.16 of the Pearson Edexcel A-level Biology A (Salters Nuffield) specification but as this is potentially the last lesson in this topic, lots of questions and activities have been included that will challenge the students on their knowledge of topic 4 (Biodiversity and Natural Resources). Hours of research went into the planning of this lesson to source interesting examples to increase the relevance of the biological content and although the main focus of the lesson is the two ex situ conservation methods, the lesson begins with a consideration of the importance of the in situ methods that are used in the Lake Télé Community reserve in the Republic of Congo and the marine conservation zone in the waters surrounding Tristan da Cunha. Students will learn how this form of active management conserves habitats and species in their natural environment, with the aim of minimising human impact whilst maintaining biodiversity. To enrich their understanding of ex situ conservation, the well-known examples of ZSL London zoo, Kew Gardens and the Millennium Seed Bank Project in Wakehurst are used. Students will understand how conserving animal species outside of their natural habitat allows for human intervention that ensures the animals are fed and given medical assistance when needed as well as reproductive assistance to increase the likelihood of the successful breeding of endangered species. An emphasis is placed on the desire to reintroduce the species into the wild and the example of some initial successes with the mountain chicken frog in Dominica and Montserrat is discussed. As stated in the specification point, these methods must be evaluated and therefore the issues are also considered and there is a focus on the susceptibility of captive populations to diseases as a result of their limited genetic diversity. The final part of the lesson considers how seed banks can be used to ensure that plant species, which may contain the molecules for medicine development, avoid extinction, and how the plants can be bred asexually to increase plant populations quickly. Due to the extensiveness of this lesson, it is estimated that it will take in excess of 2/3 hours of allocated A-level teaching time to cover the tasks and content included in the lesson and as explained above, it can also be used as revision of topic 4 content

This lesson evaluates the methods used by zoos and seed banks in the conservation of endangered species and their genetic diversity. The PowerPoint and accompanying resources have been primarily designed to cover point 4.21 of the Edexcel International A-level Biology specification but as this is potentially the last lesson in this topic, lots of questions and activities have been included that will challenge the students on their knowledge and understanding of topic 4 (Plant structure and function, Biodiversity and Conservation). Hours of research went into the planning of this lesson to source interesting examples and although the main focus of the lesson is the zoo and seed banks as ex situ conservation methods, the lesson begins with a consideration of the importance of the in situ methods that are used in the Lake Télé Community reserve in the Republic of Congo and the marine conservation zone in the waters surrounding Tristan da Cunha. Students will learn how this form of active management conserves habitats and species in their natural environment, with the aim of minimising human impact whilst maintaining biodiversity. To enrich their understanding of ex situ conservation, the well-known examples of ZSL London zoo, Kew Gardens and the Millennium Seed Bank Project in Wakehurst are used. Students will understand how conserving animal species outside of their natural habitat allows for human intervention that ensures the animals are fed and given medical assistance when needed as well as reproductive assistance to increase the likelihood of the successful breeding of endangered species. An emphasis is placed on the desire to reintroduce the species into the wild and the example of some initial successes with the mountain chicken frog in Dominica and Montserrat is discussed. As stated in the specification point, these methods must be evaluated and therefore the issues are also considered and there is a focus on the susceptibility of captive populations to diseases as a result of their limited genetic diversity. The final part of the lesson considers how seed banks can be used to ensure that plant species, which may contain the molecules for medicine development, avoid extinction, and how the plants can be bred asexually to increase plant populations quickly. Due to the extensiveness of this lesson, it is estimated that it will take in excess of 2/3 hours of allocated A-level teaching time to cover the tasks and content included in the lesson and as explained above, it can also be used as revision of topic 4 content

This is a fully-resourced lesson which uses exam-style questions, quiz competitions, quick tasks and discussion points to challenge students on their understanding of topics B1 - B5, that will assessed on PAPER 1. It has been specifically designed for students on the Pearson Edexcel GCSE Combined Science course who will be taking the FOUNDATION TIER examinations but is also suitable for students taking the higher tier who need to ensure that the fundamentals are known and understood. The lesson has been written to take place at the local hospital where the students have to visit numerous wards and clinics and the on-site pharmacy so that the following sub-topics can be covered: Cancer as the result of uncontrolled cell division The production of gametes by meiosis Mitosis and the cell cycle Sex determination The difference between communicable and non-communicable diseases The pathogens that spread communicable diseases Identification of communicable diseases Treating bacterial infections with antibiotics Evolution of antibiotic resistance in bacteria Vaccinations Genetic terminology Genetic diagrams Structures involved in a nervous reaction A Reflex arc Risk factors Chemical and physical defences Osmosis and percentage gain and loss Fossils as evidence for human evolution In order to maintain challenge whilst ensuring that all abilities can access the questions, the majority of the tasks have been differentiated and students can ask for assistance sheets when they are unable to begin a question. Step-by-step guides have also been written into the lesson to walk students through some of the more difficult concepts such as genetic diagrams and evolution by natural selection. Due to the extensiveness of this revision lesson, it is estimated that it will take in excess of 3 teaching hours to complete the tasks and therefore this can be used at different points throughout the duration of the course as well as acting as a final revision before the PAPER 1 exam.

This fully-resourced lesson describes how natural selection leads to behavioural, anatomical and physiological adaptations. The PowerPoint and accompanying resources have been designed to cover specification points 4.3 & 4.4 of the Pearson Edexcel A-level Biology A specification President Trump’s error ridden speech about antibiotics is used at the beginning of the lesson to remind students that this is a treatment for bacterial infections and not viruses as he stated. Moving forwards, 2 quick quiz competitions are used to introduce MRSA and then to get the students to recognise that they can use this abbreviation to remind them to use mutation, reproduce, selection (and survive) and allele in their descriptions of evolution through natural selection. The main task of the lesson challenges the students to form a description that explains how this strain of bacteria developed resistance to methicillin to enable them to see the principles of natural selection. This can then be used when describing how the anatomy of the modern-day giraffe has evolved over time. The concept of convergent evolution is introduced and links are made to the need for modern classification techniques as this is covered later in topic 4. Moving forwards, students will understand how natural selection leads to adaptations and a quick quiz competition introduces the different types of adaptation and a series of tasks are used to ensure that the students can distinguish between anatomical, behavioural and physiological adaptations. The Marram grass is used to test their understanding further, before a step by step guide describes how the lignified cells prevent a loss of turgidity. Moving forwards, the students are challenged to explain how the other adaptations of this grass help it to survive in its environment. A series of exam-style questions on the Mangrove family will challenge them to make links to other topics such as osmosis and the mark schemes are displayed to allow them to assess their understanding. The final part of the lesson focuses on the adaptations of the anteater but this time links are made to the upcoming topic of taxonomy so that students are prepared for this lesson on species and classification hierarchy. Due to the extensiveness of this lesson and the detail contained within the resources, it is estimated that it will take in excess of 2 hours of allocated A-level teaching time to deliver this lesson.

This detailed lesson describes the role of haemoglobin in the transport of respiratory gases and compares the dissociation curves for foetal and adult haemoglobin. The PowerPoint and accompanying resource have been designed to cover points 4.5 (i), (ii) and (iv) of the Edexcel A-level Biology B specification. The structure of haemoglobin was covered during topic 1, so the start of the lesson acts as a prior knowledge check where the students are challenged to recall that it is a globular protein which consists of 4 polypeptide chains. A series of exam-style questions are then used to challenge them to make the link between the solubility of a globular protein and its role in the transport of oxygen from the alveoli to the respiring cells. Moving forwards, the students will learn that each of the 4 polypeptide chains contains a haem group with an iron ion attached and that it is this group which has a high affinity for oxygen. Time is taken to discuss how this protein must be able to load (and unload) oxygen as well as transport the molecules to the respiring tissues. Students will plot the oxyhaemoglobin dissociation curve and the S-shaped curve is used to encourage discussions about the ease with which haemoglobin loads each molecule. At this point, foetal haemoglobin and its differing affinity of oxygen is introduced and students are challenged to predict whether this affinity will be higher or lower than adult haemoglobin and to represent this on their dissociation curve. The remainder of the lesson looks at the different ways that carbon dioxide is transported around the body that involve haemoglobin. Time is taken to look at the dissociation of carbonic acid into hydrogen ions so that students can understand how this will affect the affinity of haemoglobin for oxygen in an upcoming lesson on the Bohr effect.

This fully-resourced lesson describes the different effects that gene mutations can have on the amino acid sequence of a protein. The engaging and detailed PowerPoint and accompanying resources have been designed to cover points 1.4 (viii) & (ix) as detailed in the Edexcel A-level Biology B specification and includes substitutions, deletions and insertions and considers a real life example in sickle cell anaemia. In order to understand how a change in the base sequence can affect the order of the amino acids, students must be confident in their understanding and application of protein synthesis which was covered earlier in this topic. Therefore, the start of the lesson focuses on transcription and translation and students are guided through the use of the codon table to identify amino acids. Moving forwards, a task called known as THE WALL is used to introduce to the names of three types of gene mutation whilst challenging the students to recognise three terms which are associated with the genetic code. The main focus of the lesson is substitutions and how these mutations may or may not cause a change to the amino acid sequence. The students are challenged to use their knowledge of the degenerate nature of the genetic code to explain how a silent mutation can result. Students will learn that a substitution is responsible for the new allele that causes sickle cell anaemia and they are tested on their understanding through an exam-style question. As with all of the questions, a mark scheme is included in the PowerPoint which can be displayed to allow the students to assess their understanding. The rest of the lesson looks at base deletions and base insertions and students are introduced to the idea of a frameshift mutation. One particular task challenges the students to evaluate the statement that base deletions have a bigger impact on primary structure than base substitutions. This is a differentiated task and they have to compare the fact that the reading frame is shifted by a deletion against the change in a single base by a substitution

This fully-resourced lesson describes the light-dependent stage, including the production of ATP by cyclic and non-cyclic photophosphorylation. The detailed PowerPoint and accompanying resources have been designed to cover specification points 5.7 (ii) & (iii) of the Edexcel A-level Biology course and has been planned to link with the previous lesson on the structure of the chloroplast and to prepare for the next lesson on the light-independent stage. This is a topic which students tend to find difficult so this lesson has been intricately planned to walk them through each of the key steps of the light-dependent stage. Time is taken to describe the roles of the major protein complexes that are embedded in the thylakoid membrane and this includes the two photosystems, the proton pump and ATP synthase. A series of exam-style questions have been written that link to other biological topics in this course such as cell structure and membrane transport as well as application questions to challenge them to apply their understanding. Some of these resources have been differentiated to allow students of differing abilities to access the work and to be pushed at the same time. Students will learn that there are two pathways that the electron can take from PSI and at the completion of the two tasks which describe each of these pathways, they will understand how ATP is generated in non-cyclic and cyclic fashion. The final task of the lesson asks them to compare these two forms of photophosphorylation to check that they understand when photolysis is involved and reduced NADP is formed. Due to the detail included in this lesson, it is estimated that it will take in excess of 2.5 hours of allocated A-level teaching time to complete.

This lesson describes how the Hardy-Weinberg equation can identify changes in allele frequency that can be the result of mutation and natural selection. The detailed PowerPoint and accompanying resources have been designed to cover points 4.20 (i) & (ii) of the Edexcel International A-level Biology specification The lesson begins with a focus on the equation to ensure that the students understand the meaning of each of the terms. The recessive condition, cystic fibrosis, is used as an example so that students can start to apply their knowledge and assess whether they understand which genotypes go with which term. Moving forwards, a step-by-step guide is used to show students how to answer a question. Tips are given during the guide so that common misconceptions and mistakes are addressed immediately and then students are given the opportunity to apply their knowledge to a set of 3 questions, which have been differentiated so that all abilities are able to access the work and be challenged The rest of the lesson focuses on describing how the mutations which create the variation needed for natural selection to occur can be given as reasons for any change in allele frequency. 2 quick quiz competitions are used to introduce MRSA and then to get the students to recognise that they can use this abbreviation to remind them to use mutation, reproduce, selection (and survive) and allele in their descriptions of evolution through natural selection. The main task of the lesson challenges the students to form a description that explains how this strain of bacteria developed resistance to methicillin to enable them to see the principles of natural selection. This can then be used when describing how the anatomy of the modern-day giraffe has evolved over time.

This lesson explains the effects of light intensity, carbon dioxide concentration and temperature (limiting factors) on the rate of photosynthesis. The PowerPoint and accompanying resources have been designed to cover points (1 & 2) of the CIE A-level Biology specification (for assessment in 2025-2027) and also considers how knowledge of these limiting factors can be used to increase crop yields in the protected environment of a greenhouse. The lesson has been specifically written to tie in with the previous lessons in topic 13.1 which covered the structure of the chloroplast, the light-dependent reactions and the light-independent reactions. Exam-style questions are included throughout the lesson and these require the students to explain why light intensity is important for both reactions as well as challenging them on their ability to describe how the relative concentrations of GP, TP and RuBP would change as carbon dioxide concentration decreases. There are also links to previous topics such as enzymes when they are asked to explain why an increase in temperature above the optimum will limit the rate of photosynthesis. Step by step guides are included to support them to form some of the answers and mark schemes are always displayed so that they can quickly assess their understanding and address any misconceptions. The final part of the lesson provides details of the World’s largest rooftop greenhouse in Montreal and challenges their knowledge of related topics such as cellulose structure, pollination and biological control.

This lesson outlines the need for energy in living organisms, and describes how ATP is formed by phosphorylation in respiration and photosynthesis. The engaging and detailed PowerPoint and accompanying resources have been primarily designed to cover points 12.1 (a, b, c & e) of the CIE A-level Biology specification but can be used as a revision of topics 1, 4 and 6 as the students knowledge of cell structure, membrane transport and ATP is constantly challenged. As this is the first lesson in topic 12 (respiration), it has been specifically planned to act as an introduction to this cellular reaction and provides important details about glycolysis, the Krebs cycle and oxidative phosphorylation that will support the students to make significant progress when these stages are covered during individual lessons. Photophosphorylation is also introduced so students are prepared for the light-dependent reaction of photosynthesis in topic 13. The main focus of the start of the lesson is the demonstration of the need for energy in a variety of reactions that occur in living organisms. Students met ATP in topics 1 and 6, so a spot the errors task is used to check on their recall of the structure and function of this molecule. This will act to remind them that the release of energy from the hydrolysis of ATP can be coupled to energy-driven reactions in the cell such as active transport and a series of exam-style questions are used to challenge them on their knowledge of this form of membrane transport. They will also see how energy is needed for protein synthesis and DNA replication and the maintenance of resting potential, before more questions challenge them to apply their knowledge of cell structure and transport to explain how it is needed during the events at a synapse. The rest of the lesson focuses on the production of ATP by substrate-level, oxidative and photophosphorylation and the students will learn when ATP is formed by each of these reactions and will see how the electron transport chain in the membranes in the mitochondria and chloroplast is involved

This engaging lesson presentation (52 slides) and associated worksheets uses exam questions with displayed mark schemes, quick tasks and quiz competitions to enable students to assess their understanding of the topics found within module B2 of the OCR Gateway A Combined Science specification. The topics which are specifically tested within the lesson include: Diffusion, Osmosis, Active transport, Exchange and transport, Circulatory system, Heart and blood, Plant transport systems, Students will enjoy the competitions such as "Where's Lenny?" and "Take the Hotseat" whilst being able to recognise those areas which need their further attention.

An engaging lesson presentation (88 slides) and associated worksheets that uses a combination of exam questions, quick tasks and quiz competitions to help the students to assess their understanding of the topics found within module B3 of the OCR Gateway A GCSE Biology specification. The topics that are tested within the lesson include: Nervous system Reflexes Hormones Negative feedback The menstrual cycle Controlling reproduction Using hormones to treat infertility Controlling body temperature Controlling blood sugar Maintaining water balance Inside the kidney Students will be engaged through the numerous activities including quiz rounds like "Have they got the right BALANCE?" and "Take the IVF Hotseat" whilst crucially being able to recognise those areas which need further attention

This fully-resourced lesson explores how the structure of arteries, arterioles, capillaries, venules and veins relate to their functions. The engaging and detailed PowerPoint and accompanying resources have been designed to cover point 3.1.2 © of the OCR A-level Biology A specification. This lesson has been written to build on any prior knowledge from GCSE or earlier in this topic to enable students to fully understand why a particular type of blood vessel has particular features. Students will be able to make the connection between the narrow lumen and elastic tissue in the walls of arteries and the need to maintain the high pressure of the blood. A quick version of the GUESS WHO game is used to introduce smooth muscle and collagen in the tunica media and externa and again the reason for their presence is explored and explained. Moving forwards, it is quite likely that some students will not be aware of the transition vessels that are the arterioles. This section begins with an understanding of the need for these vessels because the structural and functional differences between arteries and capillaries is too significant. The action of the smooth muscle in the walls of these vessels is discussed and students will be challenged to describe a number of situations that would require blood to be redistributed. The middle part of the lesson looks at the role of the capillaries in exchange and links are made to diffusion to ensure that students can explain how the red blood cells pressing against the endothelium results in a short diffusion distance. The remainder of the lesson considers the structure of the veins and students are challenged to explain how the differences to those observed in arteries is due to the lower blood pressure found in these vessels. It is estimated that it will take at least 2 hours of allocated A-level Biology teaching time to cover the detail included in this lesson

This lesson describes the light-dependent stage, focusing on the production of ATP by photophosphorylation and reduced NADP. The detailed PowerPoint and accompanying resources have been designed to cover the details of points 7, 8, 9 and 10 of topic 13.1 of the CIE A-level Biology specification. The light-dependent stage of photosynthesis is a process which students can find difficult to understand in the necessary detail so this lesson has been planned to walk them through all of the key details. Time is taken to describe the roles of the major protein complexes that are embedded in the thylakoid membrane and this includes the two photosystems, the cytochrome proton pump and ATP synthase. A series of exam-style questions have been written that link to other biological topics in this course such as eukaryotic cell structures and membrane transport as well as application questions to challenge them to apply their understanding. Some of these resources have been differentiated to allow students of differing abilities to access the work and to be pushed at the same time. Students will learn that there are two pathways that the electron can take from PSI and at the completion of the two tasks which describe each of these pathways, they will understand how ATP is generated in non-cyclic and cyclic photophosphorylation. The final task of the lesson asks them to compare these two forms of photophosphorylation to check that they understand when photolysis is involved and reduced NADP is formed. Due to the detail included in this lesson, it is estimated that it will take up to 3 hours of allocated A-level teaching time to complete.

This lesson describes the relationship between the structure of the chloroplast and the functions related to photosynthesis . This fully-resourced lesson, which consists of an engaging PowerPoint and accompanying resources, has been designed to cover points (1, 2 and 3) of topic 13.1 of the CIE A-level Biology specification. The lesson introduces students to the grana and stroma as the site of the light-dependent and light-independent stages respectively before they are covered in greater detail in the lessons that are taught later in topic 13.1. Students were introduced to eukaryotic cells and their organelles in topic 1 so this lesson has been written to test and to build on that knowledge. A version of the quiz show POINTLESS runs throughout the lesson and this maintains engagement whilst challenging the students to recall the parts of the chloroplast based on a description which is related to their function. The following structures are covered in this lesson: double membrane thylakoids (grana) stroma intergranal lamellae starch grains chloroplast DNA and ribosomes Once each structure has been recalled, a range of activities are used to ensure that key details are understood such as the role of the thylakoid membranes in the light-dependent reactions and the importance of ATP and reduced NADP for the reduction of GP to TP in the Calvin cycle. Links to other topics are made throughout and this is exemplified by the final task of the lesson where students are challenged on their recall of the structure, properties and function of starch, as originally covered in topic 2.2

This lesson describes the structure of enzymes and explains how their specificity enables them to act as catalysts intracellularly and extracellularly. The engaging PowerPoint and accompanying resources have been designed to cover points 1.5 (i), (ii), (iii) & (vii) of the Edexcel A-level Biology B specification and describes Fischer’s lock and key hypothesis and Koshland’s induced-fit model to deepen student understanding of the mechanism of enzyme action The lesson has been specifically planned to tie in with topic 1.3 where protein structure and globular proteins were covered. This prior knowledge is tested through a series of exam-style questions along with current understanding and mark schemes are included in the PowerPoint so that students can assess their answers. Students will learn that enzymes are large globular proteins which contain an active site that consists of a small number of amino acids. Emil Fischer’s lock and key hypothesis is introduced to enable students to recognise that their specificity is the result of an active site that is complementary in shape to a single type of substrate. Time is taken to discuss key details such as the control of the shape of the active site by the tertiary structure of the protein. The induced-fit model is described so students can understand how the enzyme-susbtrate complex is stabilised and then students are challenged to order the sequence of events in an enzyme-controlled reaction. The lesson finishes with a focus on ATP synthase, DNA helicase and DNA polymerase and students are challenged on their recall of DNA replication with an exam question before they are challenged on their knowledge of carbohydrates, lipids and proteins from topics 1.1 - 1.3 as they have to recognise some extracellular digestive enzymes from descriptions of their substrates.