SL Content Statements

• B1.2.1

  Generalized structure of an amino acid

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  Students should be able to draw a diagram of a generalized amino acid showing the alpha carbon atom with amine group, carboxyl group, R-group and hydrogen attached.
  

• B1.2.2

  Condensation reactions forming dipeptides and longer chains of amino acids

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  Students should be able to write the word equation for this reaction and draw a generalized dipeptide after modelling the reaction with molecular models.
  

• B1.2.3

  Dietary requirements for amino acids

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  Essential amino acids cannot be synthesized and must be obtained from food. Non-essential amino acids can be made from other amino acids. Students are not required to give examples of essential and non- essential amino acids. Vegan diets require attention to ensure essential amino acids are consumed.
  

• B1.2.4

  Infinite variety of possible peptide chains

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  Include the ideas that 20 amino acids are coded for in the genetic code, that peptide chains can have any number of amino acids, from a few to thousands, and that amino acids can be in any order. Students should be familiar with examples of polypeptides.

• B1.2.5

  Effect of pH and temperature on protein structure

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  Include the term “denaturation”.
  

AHL Content Statements

• B1.2.6

  Chemical diversity in the R-groups of amino acids as a basis for the immense diversity in protein form and function
  

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  Students are not required to give specific examples of R-groups. However, students should understand that R-groups determine the properties of assembled polypeptides. Students should appreciate that R- groups are hydrophobic or hydrophilic and that hydrophilic R-groups are polar or charged, acidic or basic.
  

• B1.2.7

  Impact of primary structure on the conformation of proteins

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  Students should understand that the sequence of amino acids and the precise position of each amino acid within a structure determines the three-dimensional shape of proteins. Proteins therefore have precise, predictable and repeatable structures, despite their complexity.
  

• B1.2.8

  Pleating and coiling of secondary structure of proteins

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  Include hydrogen bonding in regular positions to stabilize alpha helices and beta-pleated sheets.
  

• B1.2.9

  Dependence of tertiary structure on hydrogen bonds, ionic bonds, disulfide covalent bonds and hydrophobic interactions

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  Students are not required to name examples of amino acids that participate in these types of bonding, apart from pairs of cysteines forming disulfide bonds. Students should understand that amine and carboxyl groups in R-groups can become positively or negatively charged by binding or dissociation of hydrogen ions and that they can then participate in ionic bonding.
  

• B1.2.10

  Effect of polar and non-polar amino acids on tertiary structure of proteins

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  In proteins that are soluble in water, hydrophobic amino acids are clustered in the core of globular proteins. Integral proteins have regions with hydrophobic amino acids, helping them to embed in membranes.
  

• B1.2.11

  Quaternary structure of non-conjugated and conjugated proteins

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  Include insulin and collagen as examples of non-conjugated proteins and haemoglobin as an example of a conjugated protein.
  NOS: Technology allows imaging of structures that would be impossible to observe with the unaided senses. For example, cryogenic electron microscopy has allowed imaging of single-protein molecules and their interactions with other molecules.
  

• B1.2.12

  Relationship of form and function in globular and fibrous proteins

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  Students should know the difference in shape between globular and fibrous proteins and understand that their shapes make them suitable for specific functions. Use insulin and collagen to exemplify how form and function are related.