Structure & role of amino acids (WJEC A-level Biology)

As the monomers of proteins, amino acids are extremely important and this lesson describes their structure and roles in organisms. The engaging PowerPoint has been designed to cover point (h) as detailed in AS unit 1, topic 1 of the WJEC A-level Biology specification and provides a clear introduction to the following lesson on the protein structures.

The lesson begins with a prior knowledge check, where the students have to use the 1st letters of 4 answers to uncover a key term. This 4-letter key term is gene and the lesson begins with this word because it is important for students to understand that these sequences of bases on DNA determine the specific sequence of amino acids in a polypeptide. Moving forwards, students are given discussion time to work out that there are 64 different DNA triplets and will learn that these encode for the 20 amino acids that are common to all organisms. The main task of the lesson is an observational one, where students are given time to study the displayed formula of 4 amino acids. They are not allowed to draw anything during this time but will be challenged with 3 multiple choice questions at the end. This task has been designed to allow the students to visualise how the 20 amino acids share common features in an amine and an acid group. A quick quiz round introduces the R group and time is taken to explain how the structure of this side chain is the only structural difference, before cysteine is considered in greater detail due to the presence of sulfur atoms. Students are briefly introduced to disulfide bridges so they will recognise how particular bonds form between the R groups in the tertiary structure which is covered in the next lesson. One more quiz round called LINK TO THE FUTURE is used to demonstrate the range of roles played by amino acids in the later part of the course such as translation and mineral ions. The final part of the lesson considers challenges the students on their knowledge of hydrolysis reactions as they have to spot the errors in a passage about the breakdown of polypeptides and dipeptides.