Protein Structure 1 Protein Structure What are the levels of protein structure and what role do functional groups play? Why? Proteins accomplish many cellular tasks such as facilitating chemical reactions, providing structure, and carrying information from one cell to another. How a protein chain coils up and folds determines its three-dimensional shape. Its shape will, in turn, determine how it interacts with other molecules and thus performs its function in the cell. Model 1 – Formation of a Peptide Bond Amino acid 1 Amino acid 2 Dipeptide N C C O O H H H H N C C H H H N C C O O H H H O N C C O O H H H CH 3 R 1 R 2 CH 2 OH H 2 O + H + 1. Examine the amino acids in Model 1. a. Circle an amine group in the diagram. b. Draw a triangle around a carboxylic acid (carboxyl) group. 2. How are the amino acids similar to one another? 3. How are the amino acids different from one another?
4. How many amino acids are involved in the reaction to make a dipeptide? 5. In Model 1 the original amino acids are combined through a condensation reaction to make the dipeptide. a. What does R 1 represent in the dipeptide? b. What does R 2 represent in the dipeptide? 6. Put a box around the atoms in the amino acids that become the H 2 O molecule produced by the reaction in Model 1. 7. A peptide bond is a covalent bond linking two amino acids together in a peptide. a. Circle the peptide bond in Model 1. b. Between which two atoms in the dipeptide is the peptide bond located? c. Between what two functional groups is the peptide bond located? 8. There are 22 different amino acids found in nature. Two were shown in Model 1. Additional examples are shown below. With your group, write one or two grammatically correct sentences to describe how these amino acids are similar and how they are different. Use the terms R-group, amine group, and carboxyl group in your description. H 2 N C H COOH H H 2 N C CH 2 SH COOH H H 2 N C COOH H H 2 C C O NH 2 H 2 N C H 2 C COOH H Glycine Cysteine Asparagine Phenylalanine (Gly) (Cys) (Asn) (Phe)
Protein Structure 3 Model 2 – Protein Structure (Part A) Primary Structure Amino acid sequence: Ser – Tyr – Ala – Phe – Val – Cys – Tyr – Asp – Cys – Gly
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