Understand how protein is formed by amino acids

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1 Identify between fibrous and globular proteins Understand how protein is formed by amino acids Describe the structure of proteins using specific examples

2 Functions of proteins Fibrous proteins Globular proteins

3 Functions of proteins Fibrous proteins Structural components Elongated molecules Insoluble in water Globular proteins Operate at molecular levels (e.g. enzymes, carriers) Spherical molecules Soluble in water

4 Functions of proteins Role of protein Example Type of protein Specific function structure keratin fibrous Protective covering in hair structure collagen fibrous Connective tissue in skin enzyme polymerase globular Catalyzes anabolic reactions likedna synthesis signalling insulin globular Controls and maintains level of glucose in blood transport hemoglobin globular Carries oxygen

5 Structure of Amino Acid 2-amino acids the chain is numbered starting with the carboxylic acid group, the amino group is attached to carbon 2.

6 Amino acids There are 20 different amino acids (R groups) Create many different proteins More can be created in the lab Exception Two extra amino acids used in a few organisms

7 Polypeptides Amino acids linked together by condensation reaction forming a peptide bond

8 Structure of Amino Acid Unassociated form zwitterion / internal salts Internal acid-base reaction, the H from COOH goes to amino group

9 Melting Point and Solubility Soluble in water Exist as crystalline solid structures Formation of zwitterion creates high melting points for solid structure Insoluble in nonpolar solvents because of the lack of attraction between the solvent molecules and the zwitterions

10 Type of Amino Acids R group dictates the type of amino acids 1. Polar (hydrophillic, likes water) 2. Non-polar (hydrophobic, doesn t like water) 3. Acidic 4. Basic

11 Type of Amino Acids R group contains = hydrocarbons hydrophobic R group contains = OH, SH, amide Can hydrogen bond with other molecules Strong intermolecular forces Hydrophillic Contains carboxylic acid COOH Negatively charged Contains amino NH 2 Positively charged

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13 R groups that are acidic or basic Amphoteric/amphiprotic accept and donate H+ according to changes in the ph Acting as an acid, donating H+ High ph Low ph Acting as an base, accepting H+

14 Electrically neutral

15 Structure of proteins 1. Primary structure 2. Secondary structure 3. Tertiary structure 4. Quatenary structure

16 Primary Protein Structure The number and sequence of amino acids in its polypeptide chain Forms covalent backbone

17 Secondary Protein Structure Hydrogen bonding of the peptide back bond causes the amino acids to fold into repeating pattern α-helix and β-pleated sheet

18 α-helix Most common secondary structure Hydrogen bonds forming between two peptide between 2 4 amino acid units apart 3.6 amino acids per turn Flexible and elastic

19 β-pleated sheet Cross-linked by interchain hydrogen bonds Flexible but inelastic

20 Tertiary Protein Structure 3D folding pattern of protein due to R group interactions Conformation protein s specific compact 3D structure

21 Tertiary Protein Structure Interactions Hydrophobic interaction H-bonding Ionic bonding Disulfide bridges Description Between non-polar R groups Between polar R groups Between R groups that carry a charge -SH and -SH R groups (only cysteine) Covalent bond strongest

22 Quatenary Protein Structure Consists of more than one amino acid chain Interaction between polypeptide chains Same interactions as tertiary