Dr. J. Venables Northwestern High School Chemistry 2 Honors Biochemistry Lesson 5-4 Dr. J. Venables Northwestern High School

Introduction to Biochemistry The chemistry of living organisms is called biochemistry. Biochemical molecules tend to be very large and difficult to synthesize. Most biologically important molecules are polymers, called biopolymers. Biopolymers fall into three classes: proteins, carbohydrates, and nucleic acids.

Proteins Amino Acids Proteins are large molecules present in all cells. They are made up of 2-amino acids. (this means that the amine group is on carbon number 2, while the carboxylic acid group is on carbon number 1)

Proteins Structure of 2-Amino Acids Carbon 2: contains amine group Carbon 1: carboxyl group Functional group – where one amino acid differs from the others

There are about 20 amino acids found in most proteins. Each amino acid is assigned a three-letter abbreviation. Our bodies can synthesize about 10 amino acids. Essential amino acids are the other 10 amino acids, which have to be ingested (part of our diet).

Polypeptides and Proteins Proteins are polyamides. When formed by amino acids, each amide group is called a peptide bond. Peptides are formed by condensation of the -COOH group of one amino acid and the NH group of another amino acid. Water is also produced in the reaction

Protein Structure Primary structure is the sequence of the amino acids in the protein. Example: NH2-leu-his-ala-…-ala-val-ser-COOH A change in one amino acid can alter the biochemical behavior of the protein. Secondary structure is the regular arrangement of segments of protein. One common secondary structure is the -helix. Contains hydrogen-bonding parallel to helix

Another is the β-pleated sheet. Contains H-bonding perpendicular to the sheet The helix or pleated sheet is held together by hydrogen bonds between N-H bonds and carbonyl groups.

Tertiary Structure is the overall shape of the protein. Fibrous Proteins – provide strength for tissue (muscle, hair, cartilage) Globular Proteins (sphere-shaped) Transport and store nutrients Catalyze reactions (enzymes) Fight invasion Participate in metabolism

Forces Affecting Tertiary Structure: Ionic Bonding Hydrogen Bonding Covalent Bonds (disulfide linkage) London Dispersion Forces Dipole-dipole Forces Denaturation – A change in the function of a protein as a result of a change in tertiary structure.

Quaternary Structure How multiple polypeptide chains are held together in large proteins containing more than one polypeptide molecule Intermolecular forces (H-bonds, dipole-dipole, LDF)

Major Functions of Proteins Structure – fibrous proteins Muscle, cartilage, skin, bones, hair, nails Collagen (skin), keratin (hair) Enzymes – Catalyze specific chemical reactions in the body. Movement and storage of energy and nutrients Protection –antibodies Control - hormones

Action of Enzymes (biological catalysts) Increases the rate of the reaction by decreasing activation energy. Action of enzyme is determined by tertiary and quaternary structure. Substrate – the “reactant” molecule in the catalyzed reaction. Active Site – the specific site on the enzyme molecule that catalyzes the reaction.

Enzymes

Inhibitor – A substance that attaches to enzyme and slows down (inhibits) the action of the enzyme Irreversible inhibition – occurs if the inhibitor bonds covalently to the enzyme Reversible if weak forces are present (H-bonds, dipole-dipole, LDF) Competitive Inhibition – The inhibitor attaches at the active site, preventing the substrate from binding with the enzyme. (example is CO or CN-) To reduce the effect, we can increase the substrate concentration

Non-competitive inhibition – Inhibitor binds to the enzyme at a site other than the active site. This causes the shape of the active site to change, so that the enzyme will no longer fit into the active site properly. (heavy metal ions)

Effect of Temperature on enzyme action Most efficient at body temperature. As temperature increases or decreases, tertiary structure changes, altering active site.

Effect of pH on enzyme action Each enzyme has an optimal pH. The further you get from that pH, the less effective it is (denaturation occurs)

Uses of Enzymes in Biotechnology Fermentation – production of alcohol Wine – yeasts in grape skin turn sugars into alcohol 2 (C6H10O5)n + n H2O n C12H22O11 C12H22O11 + H2O 2 C6H12O6 C6H12O6 2 C2H5OH + 2 CO2 Cheese manufacture – fermentation of lactose. Penicillin – fermentation to make antibiotic. Enzyme immobilization Genetic Engineering (anti-virals)