<span>The "Holocaust" refers to the period from January 30, 1933, when Hitler became Chancellor of Germany, to May 8, 1945 (V-E Day), the end of the war in Europe.</span>
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.
Vasco da Gama
did NOT lead an exploratory expedition
Answer: found this on a wiki hope it helps. Emmett Louis Till (July 25, 1941 – August 28, 1955) was a 14-year-old African American who was lynched in Mississippi in 1955, after being accused of offending a white woman in her family's grocery store. The brutality of his murder and the fact that his killers were acquitted drew attention to the long history of violent persecution of African Americans in the United States. Till posthumously became an icon of the civil rights movement.[1]
Till was born and raised in Chicago, Illinois. During summer vacation in August 1955, he was visiting relatives near Money, in the Mississippi Delta region. He spoke to 21-year-old Carolyn Bryant, the white married proprietor of a small grocery store there. Although what happened at the store is a matter of dispute, Till was accused of flirting with or whistling at Bryant. In 1955, Bryant had testified that Till made physical and verbal advances. The jury did not hear Bryant's testimony, due to the judge ruling it inadmissible.[2][3] Decades later, historian Timothy Tyson interviewed Bryant and wrote a book in which he claimed that she had disclosed that she had fabricated part of the testimony regarding her interaction with Till, specifically the portion where she accused Till of grabbing her waist and uttering obscenities; "That part's not true," Tyson claimed that Bryant stated in a 2008 interview with him.[2][4][5] Till's interaction with Bryant, perhaps unwittingly if at all, violated the strictures of conduct for an African-American male interacting with a white woman in the Jim Crow-era South.[6] Several nights after the incident in the store, Bryant's husband Roy and his half-brother J.W. Milam were armed when they went to Till's great-uncle's house and abducted the boy. They took him away and beat and mutilated him before shooting him in the head and sinking his body in the Tallahatchie River. Three days later, Till's body was discovered and retrieved from the river.
Explanation:
In Mesopotamia they used irrigation canals to bring water to crops.
