Chemical Reactions Breaking of bonds forming of new ones. New combinations of atoms are produced forming new substances with new properties. Energy needs to be conserved in cells

What is a Metabolic Reaction? Metabolism= all the chemical reactions in your body, EX. Cellular respiration: glucose + oxygen  energy+CO 2 +H 2 0 Q. Which are the reactants? Q. Which are the products? Q. What shows the direction of the reaction? Catabolism: Break down of larger molecules into smaller, Ex: proteins to amino acids Anabolism: building of complex molecules from smaller ones, Ex: amino acids to proteins

Bond Energy Energy is often a trigger for reactions, ex. heat from a match to start wood burning. Break the bonds between oxygen and glucose Bond energy: amount of energy needed to break bonds between atoms. This energy varies depending on types of bonds and atoms involved Energy released when bonds form, same amount of energy is then needed to break them

Chemical Equilibrium Some reactants get used up in a chemical reaction, then it stops Some chemical reactions move in both directions One direction then the other depending on concentrations of reactants and products Ex: CO 2 + H 2 O  H 2 CO 3  Carbonic anhydrase speeds up reaction Equilibrium Reactants and products made at the same rate

Chemical reactions release or absorb energy Whether a reaction releases or absorbs energy depends on bond energy Some energy is always absorbed by the reactants Activation Energy energy required to start a chemical reaction Exothermic Reaction: releases more energy than it absorbs, heat, light EX: Cellular respiration

Endothermic Reaction: absorbs more energy than it releases Ex: Photosynthesis, use energy from the sun to make sugars

What are Enzymes? Proteins Enzymes (proteins) are used to lower the Activation Energy required to start a chemical reaction Known as biological Catalysts, alter rate of chemical reactions (speeds up) without being changed itself. Also lowers activation energy needed Are very specific for their substrate E.X. Digestion enzymes speed up the break down of larger molecules to smaller. Different enzyme for each kind of food. Ex: lipase breaks down lipids

Temperature Cambridge Pg 41 Look at 5.2 How does temperature affect enzymes? Most reactions occur faster with higher temps, molecules move around faster. > by 10 o C = double rate of reaction. Enzymes damaged by high temps become denatured.

pH Cambridge Pg 51 Look at 5.3 what affect does pH have on enzymes activity? Work in a narrow pH range around 7 Pepsin however works in stomach very acidic conditions.

The Enzyme-Substrate Complex Enzymes provide a site for reactions to take place Enzymes have a dent known as an active site, the reactants of the reaction known as the substrate fit into it. Enzymes then break the substrate apart into smaller molecules known as the product. Enzymes can also bond reactants together

Induced Fit Model Active site and molecules do not have to match exactly. When enzymes and substrate join, shape of enzyme changes slightly making fit more exact. Coenzymes- Non protein helper molecules, often made from vitamin molecules. Some join temporarily with enzymes, changing the enzymes active site so it fits with substrate

Naming Enzymes Most enzymes are named by adding the suffix – ase to part of the name of the substrate in the reaction the enzyme controls E.x. Maltase controls conversion of Maltose to glucose. E.x. Protein> amino acids by protease Catalase found inside cells of living organisms (liver or potato), breaks down hydrogen peroxide which is very dangerous into water and oxygen.

Review: What are the main characteristics of enzymes? All proteins-specific 3D shape, active site shape specific. All are catalysts-unchanged by reaction they catalyse, can be used over and over again Become inactive by high temps over 40 o C. Work best at a particular pH usually around 7. Specific for a substrate.