What happens in practice is that banks extend loans first and worry about their reserves later. By virtue of that, the enterpreneur gets a buck to invest in whatever he's doing, and part of that buck lands as extra pay (and thus economic activity) in the hands of workers who will spend every last bit of it for all intents and purposes.
Classical economist's explanation: bank has 100, lends you 90 so as to keep 10 in reserves. 90 gets spent and part of it lands in the bank. Rinse, repeat.
What actually happens: bank has 10, lends you 100. It gets spent and part of it lands back in the bank. If it's not enough to post proper reserves, bank begs central bank for a buck or two to make things work. Rinse, repeat.
It's not an opinion by the way: it's by the own admittance of the SEC. See Steve Keen's research for more details.