The Structure of Proteins

1. The Structure of Proteins • describe, with the aid of diagrams, the structure of an amino acid; • describe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and hydrolysis of dipeptides and polypeptides; • explain, with the aid of diagrams, the term primary structure; • explain, with the aid of diagrams, the term secondary structure with reference to hydrogen bonding;

2. Protein Uses • Proteins are large molecules made up of the elements carbon, hydrogen, oxygen and nitrogen. Some proteins also contain sulphur. • Try to write down 5 uses for proteins • Structural components e.g. muscle or bone • Membrane carriers and pores for active transport and facilitated diffusion • Enzymes • Hormones • antibodies

3. H • All proteins are made of repeating units called amino acids • We call a large molecule made of repeating units a polymer • The individual sub-units (like amino acids) are called monomers • Many monomers join together to make a polymer • All amino acids have the same basic structure, an amino group at one end, a carboxyl (or acid) group at the other, and a carbon atom in between • The R group at the top stands for one of 20 sets of atoms that make all 20 amino acids different • In glycine (the simplest amino acid), the R group is just a Hydrogen atom (H)

5. Task • Using Cambridge Biology p108-109, write about how amino acids are linked together to form a ‘polypeptide’ • You must include a diagram, and must also use the key terms that follow: • Peptide bond, covalent bond, condensation reaction, polypeptide, • When finished, complete SAQ 2 a and b

7. This is now called a dipeptide. Joining more will create a polypeptide Now explain how amino acids split apart, using a diagram and a description including the key word: hydrolysis

8. Questions • What are essential amino acids? • The backbone for a molecule with 4 amino acids is: N-C-C-N-C-C-N-C-C-N-C-C, draw this out in full, showing the amino acids joined and the peptide bonds formed • How many molecules of water would be produced in forming this amino acid chain? • Why do we call this a polypeptide?

9. Questions • What are essential amino acids? amino acids found in meat mostly- animals cannot make them in the liver • The backbone for a molecule with 4 amino acids is: N-C-C-N-C-C-N-C-C-N-C-C, draw this out in full, showing the amino acids joined and the peptide bonds formed • How many molecules of water would be produced in forming this amino acid chain? 3 molecules of water will be formed • Why do we call this a polypeptide? A molecule containing many peptide bonds