Many enzymes consist of a protein and a non-protein (called the cofactor). The proteins in enzymes are usually globular. The intra- and intermolecular bonds that hold proteins in their secondary and tertiary structures are disrupted by changes in temperature and pH. This affects shapes and so the catalytic activity of an enzyme is pH and temperature sensitive.
Everyday in the U.S. millions of cars and trucks idle needlessly, sometimes for hours. You may not be able to avoid keeping your engine running when youâre stopped at a traffic signal or stuck in slow-moving traffic. But other times idling is unnecessary. An idling car can release as much pollution as a moving car.
As many have stated they vary from 400 -1000 rpm , a lot varies on engine design , true they can idle lower , but the engine runs rougher, many older cars that did not have auto trans an power steering ,an AC , which of course had small 35 amp alt, would idle in the 400 rpm range ,most of the big truck eng use to idle in the 450 - 600 rpm range ,older cars with carbs use to use a step up solenoid that adj the idle do to engine demand, ie the AC cycling on an off , putting the car in gear ...