pptx, 3.5 MB
pptx, 3.5 MB
docx, 12.35 KB
docx, 12.35 KB
docx, 16.15 KB
docx, 16.15 KB
docx, 17.49 KB
docx, 17.49 KB
docx, 13.1 KB
docx, 13.1 KB
docx, 13.86 KB
docx, 13.86 KB

This lesson describes the properties of gas exchange surfaces and shows how Fick’s law of diffusion is dependent on these properties. The PowerPoint and accompanying worksheets have been designed to cover points 2.1 (i & ii) of the Pearson Edexcel A-level Biology A (Salters Nuffield) specification and there is a particular focus on the relationship between the size of an organism or structure and its surface to volume ratio.

Adolf Fick is briefly introduced at the start of the lesson and the students will learn that his law of diffusion governs the diffusion of a gas across a membrane and is dependent on three properties. The students are likely to know that surface area is one of these properties but although they may have been introduced to the surface area to volume ratio at GCSE, their understanding of its relevance tends to be mixed. Therefore, real life examples are included throughout the lesson that emphasise the importance of this ratio in order to increase the relevance. A lot of students worry about the maths calculations that are associated with this topic so a step by step guide is included at the start of the lesson to walk them through the calculation of the surface area, the volume and then the ratio. Through worked examples and understanding checks, SA/V ratios are calculated for cubes of increasing side length and living organisms of different size. These comparative values will enable the students to conclude that the larger the organism or structure, the lower the surface area to volume ratio. A differentiated task is then used to challenge the students to explain the relationship between the ratio and the metabolic demands of an organism and this leads into the next part of the lesson, where the adaptations of a human to increase the ratio at the gas exchange surface is covered. The students will calculate the SA/V ratio of a human alveolus (using the surface area and volume formulae for a sphere) and will see the significant increase that results from the folding of the membranes. The remainder of the lesson introduces concentration difference and thickness of membrane as the other two properties in Fick’s law of diffusion and students are reminded that the maintenance of a steep concentration gradient and a reduction in the diffusion distance are critical for this transport mechanism.

This lesson has been specifically planned to prepare students for the next lesson which describes how the structure of the mammalian lung is adapted for rapid gas exchange (specification point 2.1 [iii])

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Topic 2: Genes and Health (Pearson Edexcel SNAB)

Some of the key biological topics are covered in topic 2 of the Pearson Edexcel A-level Biology A (Salters Nuffield) course and include the transport of materials across cell membranes, DNA structure and replication, protein synthesis and monohybrid inheritance. In line with this, many hours of intricate planning have gone into the design of all of the 19 lessons that are included in this bundle to ensure that the content is covered in detail, understanding is constantly checked to immediately address misconceptions and that engagement is high. This is achieved through the wide variety of tasks in the PowerPoints and accompanying worksheets which include exam-style questions with clear answers, discussion points, differentiated tasks and quick quiz competitions. The following specification points are covered by the lessons within this bundle: * The properties of gas exchange surfaces in living organisms * Understand how the rate of diffusion is dependent on these properties and can be used in the calculation of the rate of diffusion by Fick's law * Adaptations of the mammalian lung for rapid gaseous exchange * Structure and properties of cell membranes * Simple and facilitated diffusion as methods of passive transport * The involvement of ATP and carrier proteins in active transport, endocytosis and exocytosis * The basic structure of mononucleotides * The structures of DNA and RNA * The process of protein synthesis * The roles of the template strand, mRNA and tRNA * The nature of the genetic code * A gene is a sequence of bases on DNA that codes for the amino acid sequence of a polypeptide * The basic structure of an amino acid * The formation of polypeptides and proteins * The primary, secondary, tertiary and quaternary structure of proteins * Globular and fibrous proteins using haemoglobin and collagen as examples * The mechanism of action and the specificity of enzymes * Enzymes are biological catalysts that reduce activation energy * The process of DNA replication * Errors in DNA replication can give rise to mutations * The meaning of key genetic terms * Patterns of inheritance, in the context of monohybrid inheritance * Understand how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and reproductive systems * Understand the uses and implications of genetic screening and prenatal testing Due to the detail included in each of these lessons, it is estimated that it will take in excess of 2 months of allocated teaching time to cover the content. If you would like to see the quality of the lessons, download the gas exchange surfaces, cell membranes, transcription, globular and fibrous proteins, monohybrid inheritance and cystic fibrosis lessons as these have been shared for free

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