Lec 8 Protein PDF

# Lecture 8: Proteins ## **Protein** - Polymer of amino acids - Histon protein rich of basic amino acids [positive charge] ## Classification - According the shape: - **Structural**: Plays a role in the structure of a protein. They're insoluble in water. Examples are keratin and fibrous proteins...

# Lecture 8: Proteins ## **Protein** - Polymer of amino acids - Histon protein rich of basic amino acids [positive charge] ## Classification - According the shape: - **Structural**: Plays a role in the structure of a protein. They're insoluble in water. Examples are keratin and fibrous proteins - **Dynamic**: - Enzymes, hormones - Steroids, insulin, glucagon - Antibodies - Have regulatory function - Transport protein - Hemoglobin, myoglobin - Lactopheren make the immunity higher against infection - Myoglobin: storage O2 in muscles ## Chemical Classification - **Primary Structure of Protein**: The particular sequence of amino acids that is the backbone of a peptide chain or protein. A single polypeptide chain, for example, is the hair pin shape. **-Ala - Leu - Cys - Met**. ## Secondary Structure - **Alpha Helix**: Three-dimensional arrangement of amino acids with the polypeptide chain in a corkscrew shape. Held by H bonds between the H of - N-H group and the - O of C =O of the fourth amino acid along the chain. It looks like a coiled, "telephone cord". - **Beta pleated sheet**: - Poly peptide chains are arranged side by side. - Hydrogen bond between chains. - R groups of extend above and below the sheet. - Typical of fibrous proteins such as silk. - **Triple Helix**: Three poly peptide chains, woven together, like a rope. Glycin, Proline, hydroxy Proline and hydroxy lysin. H bond between - OH groups gives a strong structure. Typical of Collagen: connective tissue skin tendons and cartilage. ## Tertiary Structure. - Specific overall shape of protein. - Cross linked between R groups of amino acids in chain. - DiSulfide: S-S - H bonds: C=O No - Ionic: -Coo H3N+ - Hydrophobic: CH3 H3C- - **DiSulfide (S)**: Two Cysteines - **Ionic (acid and base)**: Aspartic acid and lysine - **H bond (Co. OH)**: Serine and threonine - **Hydrophobic CH₃**: Leucine and valine ## Protein types - **Globular protein**: Spherical shape. - Insulin - Hemoglobin. - Enzymes - Antibodies - **Fibrous protein**: are long, thin fibers. - Hair - Wool - Skin - Nail ## Quaternary Structure - Protein with two or more chains polypeptide. - Example is hemoglobin [carries oxygen in blood. Four polypeptide chains. Each chain has a heme group to bind oxygen]. ## Denaturation - **Denaturation**: Disruption of secondary, tertiary and quaternary protein structure. - **Physical**: - Heat - Pressure - Break down H bond and disrupt hydrophilic bond. - **Chemical**: - Acids/base - Break H bonds between polar R group and ionic bonds. - Strong acids/bases only are irreversible ## Protein Hydrolysis - Break down of peptide bonds. - Requires acid or base, water and heat. - Gives Smaller peptides and amino acids. - Similar to digestion of protein using enzymes in stomach. - Occurs in cells to provide amino acids to synthesize other proteins and tissues. - Water + HCL + enzyme (Catalyst) play a role in digestion. - Children need protein than people (old edge) - Decreasing of the Source of protein (to save Kidney) - Decreasing of activity of enzymes in old edge ## Application of Denaturation - Hard boiling an egg. - Wiping the skin with alcohol swab for injection. - Cooking Food to destroy E. Coli - Heat used to cauterize blood vessels. - Autoclave sterilizes instruments. - Milk is heated to make yogurt ## Some notes in Structural proteins. - **Where is the Collagen**: Skin, Cartilage, components of bones and tendon. - **Keratin**: Hair, skin, nails, bird feathers. - **Elastin**: used in contractile protein. (Energy + heat) movement - **Actin. Myosin**: In the event of a heart attack, not in normal level. - **Fibral protein**: plays a role in blood clotting # Other notes - **H₂O₂**: Milk protein, Sugar + milk = lactose - **Immunogloblin**: Exists in the cell. - **Antibodies**: defends the cell against disease. - **Globular protein**: spherical, 4:10 - **Fibrous protein**: elongatudinal, 10 or more than 10 - **Congiucated protein**: Not pure protein.