Activation Energy

• When chemical reactions occur; energy changes due to substrate structure changes and breaking/reforming bonds; exothermic release heat energy (most spontaneous reactions - bad news) and endothermic absorb heat energy
• In living organisms, released energy can be heat, light, chemical, or electrical, heat and light are lost and cannot be used, but others can; exergonic reactions release energy and endergonic reactions require energy input
• In living cells, most chemical reactions require an input of energy before the molecules can react together, called the activation energy, enzymes lower it - so the reaction can proceed quicker at lower temperatures
• This activation energy is required for the breaking of bonds in the substrates and the formation of new bonds in the products
• Enzymes provide an active site that brings the substrate close together; according to the induced fit model, the moulding of the enzyme around the substrate puts a strain on it and causes bonds to form or break