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Lesson 4 – Proteins Amino Acid Structure and the Peptide Bond

Lesson 4 – Proteins Amino Acid Structure and the Peptide Bond. Heteropolymers. Proteins are heteropolymers . The amino acids they are made of are similar but different from each other. There are only ______ different amino acids that human proteins are made from. 20. Amino Acid Structure.

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Lesson 4 – Proteins Amino Acid Structure and the Peptide Bond

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  1. Lesson 4 – ProteinsAmino Acid Structure and the Peptide Bond

  2. Heteropolymers Proteins are heteropolymers. The amino acids they are made of are similar but different from each other. There are only ______ different amino acids that human proteins are made from. 20

  3. Amino Acid Structure α-carbon

  4. Isomerism in Amino Acids Like carbohydrates, amino acids also exist as D-form and L-form isomers. The L-form is found exclusively in proteins.

  5. Ionised Forms If the pH of the solution is neutral (like in a biological system) any amino acids in solution will be ionised.

  6. R- Groups The R-groups give the amino acids their unique chemical properties. There are 4 classifications of R groups: Acidic, Basic,Uncharged polar and Nonpolar

  7. Amino Acid Classes Copy the table below and complete with the information from the slides that follow.

  8. Acidic R Groups Of the 20 amino acids there are 2 that are acidic. They both have carboxyl groups that ionise to make them acidic. -COOH Aspartic Acid Glutamic Acid Asp D Glu E

  9. Acidic R Groups Both acidic amino acids are hydrophilic. On your desks list the 2 acidic amino acids. Include their 3 letter abbreviation and single letter code. Aspartic Acid Glutamic Acid Asp D Glu E

  10. Basic R Groups There are 3 different amino acids with basic R groups. All have additional amino groups that ionise to NH3+. All are hydrophilic. Lysine is an example of a basic amino acid. -(CH2)4NH2 Lysine Lys K

  11. Uncharged Polar Groups There are 5 amino acids which are uncharged and polar. All are hydrophilic. These all have different functional groups most containing at least one –OH group. We will learn 2 – serine and asparagine. Serine Ser S Asparagine Asn N

  12. Non-polar There are 10 amino acids which are non-polar. All are hydrophobic. Their R groups are hydrocarbons. We need to know 3 of these: glycine, alanine and cysteine. Cysteine Cys C Glycine Gly G Alanine Ala A

  13. Peptide Bonds Amino acid monomers are linked together to make a polypeptide through dehydration synthesis (condensation reaction). The –OH from one amino acid bonds to the -H from the -NH2 group on another amino acid.

  14. Test Yourself On your desk draw the structure of an amino acid (just include a generic R group). Now change the R group to make it an acidic amino acid and name the one you have drawn. Now change the R group make it a basic amino acid and name the one you have drawn. Same to uncharged polar. Finally for nonpolar.

  15. Your Task- Amino Acids Past Paper Questions You will need to access these in the department. Please DO NOT TAKE past papers home – we have limited numbers. 2002 MC Q4 2004 MC Q13 2. Complete Scholar activities on amino acids. 3. Read and make notes on pages 30-35 4. Make sure your glossary is up to date. DUE Monday (November 19th)

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