What is an active site and what is its relationship to an enzyme? an active site in an enzyme is the area that breaks the bond in its substrate. E.g. a maltose molecule's glycocide bond is broken by the active site in a maltase enzyme.
The caffeine in a cup of coffee might help your small blood vessels work better. Credit: Â© jogyx / Fotolia. The caffeine in a cup of coffee might help your small blood vessels work better, according to research presented at the American Heart Association's Scientific Sessions 2013.
The Mayo Clinic warns that people who drink more than four cups of coffee a day may feel a range of side effects, including insomnia, nervousness, restlessness, irritability, stomach upset, fast heartbeat and muscle tremors. How sensitive you are to caffeine depends on a number of factors.