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.
That is good news for drivers, who are keeping their cars longer than ever before; the average age of all cars on the road is more than 11 years, up from about eight years in 1995, according to Polk research. Still, motorists might not realize the long-term financial benefits of keeping a car for 200,000 miles.