Chemical Reactions & Enzymes

I. Chemistry A. We already know that all living things are made up of chemical compounds. What are they again? Which give us energy? B. Chemistry is not only what life is made up of- chemistry is also what life does. 1. growth, interaction with environment, reproduction & movement are all based on chemical reactions

II. Chemical Reactions A. Chemical reactions: is a process that changes, or transforms one set of chemicals into another by changing bonds between atoms 1. Can occur quickly or slowly B. Chemical reactions have two parts: 1. Reactants: elements or compounds that enter the reaction (what you start with) 2. Products: elements or compounds that are produced (what you end up with)

II. Chemical Reactions Examples 2H₂ + O₂  2H₂O _______ _______ _______ _______ C₆H₁₂O₆ + 6O₂  6CO₂ + 6H₂O + ATP __________ __________

III. Energy in Reactions A. Whenever chemical bonds form or are broken energy is released or absorbed. (bioenergetics) Think about after you ingest a meal B. Energy change is a good indicator if a chemical reaction will occur. C. Chemical reactions that release energy often occur spontaneously D. Chemical reactions that absorb energy will not occur without a source of energy

III. Energy in Reactions Examples Reactions that release energy Pure Sodium + Water Reactions the absorb energy (Take the energy of stirring) Cold Packs

III. Energy in Reactions E. Types of reactions: 1. Exergonic – products have less energy than the reactants. Energy is given off. Example: food being oxidized in mitochondria of cells. 2. Endergonic – products have more energy than the reactants. Energy is required. Example: plants using CO2 and water to form sugars.

IV. Activation Energy A. The energy needed for a chemical reaction to start is known as activation energy. 1. Every cell needs a little bit of energy to begin breaking down molecules. B. Examples

V. Enzymes A. Some chemical reactions that make life possible are to slow or have very high activation energies therefore our cells compensate by making catalysts B. Catalysts are substances that speed up reactions by lowering the activation energy without altering reaction. C. Enzymes are proteins that act as catalyst inside a cell.

V. Enzyme Action First in order for any reaction to occur enough energy must be present among the reactants so bonds can break and new bonds can form. A. Enzyme-Substrate Complex: enzymes provide a site where reactants can be brought together and react. (enzymes are very specific) 1. Reactants that fit into the enzyme are known as substrates 2. The substrates bind to an area on the enzyme that is known as the active site

V. Enzyme Action B. Most enzymes have to change its shape slightly to fit its substrate. (induced fit) C. Once a reaction has occurred and the enzyme has helped form the product, it is released and the enzyme goes back to its original state to help out again.

V. Enzyme Action D. Sometimes enzymes need a little help catalyzing reactions, coenzymes help them out. 1. Examples: Vitamins, NAD+, NADP+ 2. Inorganic elements such as Fe+2 are called cofactors & can help a reaction along

VI. Regulation of Enzyme Activity A. All Enzymes: 1. Fit one specific type of substrate (think lock and key) 2. Increase activity with increasing temperature to an extent. Once temp. is to high enzyme is denatured. 3. Can be influenced by a change in pH (Optimal pH 7) 4. Increase activity with increasing amounts of substrate

VII. Types of Enzyme Regulation A. Cells control enzyme activity (metabolism) by regulating conditions that influence enzyme shape. Types of control: 1. Competitive Inhibition 2. Noncompetitive Inhibition

1. Competitive Inhibition a. Different molecules, similar in shape to the substrate, compete for the active site of the enzyme. i. fix problem by increasing amount of substrate

2. Noncompetitive Inhibition a. enzymes are allosteric – change in shape alters efficiency. b. molecules known as allosteric regulators bind to a site distinct from the active site causing a change in the enzyme shape inhibiting the enzyme to catalyze substrates. i. feedback inhibition – where the end product of a allosteric reaction can then act like an inhibitor.

Redox Reactions Redox reactions involve the transfer of electrons. Example: Electron transport chain during cellular respiration There are two parts in a redox reaction: Reduction- involves gain of electrons Oxidation- involves loss of electrons Tricks to remember this: LEO (lose electron oxidation) the lion says GER (gain electrons reduction) OIL (oxidation involves loss) RIG (reduction involves gain)

Redox Reactions