Biochemistry Tools A B synthesis two simple compounds combining together to form a more complex compound enzyme (organic catalyst) proteins that speed up the rate of chemical reactions in living things catalyst a substance that speeds up chemical reactions but is not used up during the process active site where substate and enzyme combine substate the substance acted upon by the enzyme biochemistry chemistry which takes place in living things bonds the chemical link between atoms that holds molecules together organic compounds compounds that contain both carbon and hydrogen inorganic compounds compounds that do not contain carbon and hydrogen together proteins break down into amino acids amino acids building blocks that form proteins starch break down into simple sugars simple sugars combine together to form a starch optimum temperature the temperature at which an enzyme works best at shape of protein above or below a certain temperature the active site distorts and works poorly or not at all