Each enzyme has an "active site". The active site of each enzyme is unique in terms of 3D structure. Each unique active site can be thought of as a 3D surface that is able to bind only a single unique substrate or set of substrates, and it is the shape of the active site that is responsible for each enzyme's substrate selectivity. Most enzymes actually use the same or nearly the same, mechanisms of action; most commonly simple acid-base chemistry is used to catalyse reactions.
It may be difficult to understand, but enzyme active sites are actually thought to bind the "transition state" of the substrate. The transition state may be thought of as a state where the structure of the substrate is literally stretched to be somewhere between the orginal substrate structure, and the structure of the product of the enzyme catalyzed reaction. In other words, the enzyme can be thought of as "pulling" the substrate into a product. In this way, the enzyme lowers the energy required to pass the "transition" state, and accelerates the reaction of substrate to product.
Thus, the structure of the enzyme imparts both its substrate specificity (because only certain substrates will fit into the active site), and its activity (because in binding the substrate, the enzyme lowers the transition energy required for the substrate to form product).
Hope this helped, despite my rambling.
They share the power of being able to: collect taxes, build roads, borrow money, establish courts, make and enforce laws, charter banks and corporations, spend money for the general welfare, and take private property for public purposes.
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The accomplishments of the Lewis and Clark Expedition were extensive. It altered the imperial struggle for the control of North America, particularity in the Pacific Northwest. It strengthened the U.S. claim to the areas now known as the states of Oregon and Washington.
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The Continental Army consisted of soldiers from all 13 colonies and, after 1776, from all 13 states. When the American Revolutionary War began at the Battles of Lexington and Concord on April 19, 1775, the colonial revolutionaries did not have an army.
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During world war 2, the allies were able to go on the offensive against japan after the "Battle of Midway", since this turned the war in the Pacific in the favor of the Allies due to Japan losing so many ships.