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 activationenergy, 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
