what are three general ways in which enzyme activity can be regulated?

 Enzymes, are organic catalysts that lower the activation
energy for chemical reactions to proceed.  Enzyme activity is affected by temperature,
ph and the amount of substrate available. Temperature is very important to the action of
enzymes and there is a narrow range of temperature that enzymes work optimally, usually
body temperature. If you observe a curve of temperature vs. enzyme activity, it peaks
around body temperature in humans(37 degrees Celsius) and as you go below or above that
temperature, the action of the enzyme decreases. It is a bell-shaped curve.  Enyzmes
become denatured(lose their shape) and their active site which links to the substrate
molecule, is unable to "fit" as well, therefore, enzyme action decreases. Ph works in
the same way. Enzymes work best under certain conditions of ph--either acid(as in
protease enzymes in the stomach), alkaline, or neutral. Any deviation from the optimum
ph results in the activity of enzymes decreasing. Finally, the more substrate that is
available, the more the active sites of the enzyme molecules will bind to the available
substrates. Initially, the reaction rate will increase. However, once all active sites
have bound to available substrate, there will be no further increase in the rate of
reaction. It will level off.