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What processes and characteristics need to occur for something to be considered “living”? • • • • • • • • Excretion : getting rid of waste Secretion : releases usable materials Reproduction Growth Use energy Metabolize : carry out chemical reactions Has Genetic material Made up of CELLS! How do our cells carry out all of the necessary processes of life? ENZYMES! (2.5) Proteins • 4 levels of structure • The sequence of amino acids (specifically the R-groups) determines the overall shape of a protein • The function of any proteins is dependent upon its overall shape • When a protein is denatured, the intermolecular bonds are broken, compromising the shape of the protein, and thereby losing its function. Characteristics of Enzymes • Enzymes are a specific type of protein (polypeptide) • Quaternary level structure • Speed up all types of chemical reactions by reducing the activation energy required • Do not get destroyed during reactions, but get re-used over and over again. • Are highly specific in their behavior which is determined by the shape of the enzyme • Are affected by pH and temperature • Approximately 1,300 enzymes in the human cell. • DNA = instructions for life ; Enzymes = workers that carry out those instructions • Rubisco is the most abundant enzyme in the world. What is ACTIVATION ENERGY? • Chemical reactions are due to molecules physically colliding with one another • Molecules must have enough energy to break and re-form bonds (chemical reaction) • ACTIVATION ENERGY: the amount of energy required for a chemical reaction to occur 6 Enzymes (Catalyst): speed up a reaction by stressing the bonds in the reactants, providing another chemical pathway that has a lower activation energy (Ea) • Enzymes only work to speed up reactions that are already occurring, they cannot produce reactions that would not normally occur. 7 Metabolic reactions would not be possible without enzymes • Body temperature: 37⁰C (98⁰F) • Polymers could not be digested without enzymes • Enzymes remain unchanged after a reaction has occurred • Enzymes are reused 8 Example: Catalytic Converters as Catalysts • Catalytic converters speed up the reaction that converts harmful exhaust gases into harmless products Nitrogen oxide and carbon monoxide are converted to carbon dioxide 9 and nitrogen gas How are enzymes used in our bodies? • Some enzymes have 1 specific function, while others are involved in various types of reactions. • Example Functions: – Copy DNA – Digest food – Obtain & metabolize energy from food – Synthesis of proteins – Blood clotting – Getting rid of wastes (the shape of the active site determines the function of the enzyme) How do enzymes work? – OLD MODEL The Induced Fit Model of How Enzymes Work • How Enzymes Work: http://highered.mheducation.com/sites/0072495855/s tudent_view0/chapter2/animation__how_enzymes_w ork.html Why do enzymes stop working? What factors affect the activity of an enzyme? • Temperature • pH • Concentration (amount) of substrate