POLYPEPTIDES AND PROTEINS A condensation reaction between two amino acids forms a peptide bond. Polypeptides are formed by the condensation of many amino acids. A functional protein may contain one or more polypeptides. The role of hydrogen bonds, ionic bonds and disulfide bridges in the structure of proteins. Proteins have a variety of functions within all living organisms. The relationship between primary, secondary, tertiary and quaternary structure, and protein function. The Biuret test for Proteins
Starter: Proteins are not simple Match up these post its to their definitions: Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Primary Structure The sequence of amino acids joined together is referred to as primary structure. Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Secondary Structure The amino acids form into 3-d structures. Held together by hydrogen bonds Alpha-helix Beta pleated sheets Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Tertiary Structure When the polypeptide reforms into a 3-D structure and coils up in a specific structure The chains of the polypeptide can link up and form bonds to help form the shape. Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Quaternary Structure When 2 or more polypeptides join together Same bonds as tertiary structure Complex polypeptides THIS IS A PROTEIN Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Summary of Structure Identify the different structures here: Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Structure → Function The 3-d secondary, tertiary and quaternary structure of a protein is determined by the sequence of amino acids in the primary structure. The shape of each protein is extremely specific and unique! Why is protein structure so important? Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins
Testing for Proteins Testing the sample Add 2 cm3 of the liquid food sample to a clean, dry test tube Add 2 cm3 of Biuret Reagent. Testing a negative control Repeat the steps above with de-ionized water to prepare a negative control Testing a positive control Repeat the steps above with albumin (egg white) to prepare a positive control. Shake well and allow the mixture to stand for 5 minutes. Observe any color change. Outcomes: -Name the monomers and bond that polymerises to form polypeptides -Explain and draw what is meant by the terms primary, secondary, tertiary and quaternary structure of proteins. -Explain the role of a protein is entirely dependent on its structure/shape. -Outline the test for proteins Biurets reagent is used to test for… How it works: What is the importance of using positive and negative controls?