No, but they are composed entirely of sentient beings.
Yes, but corporations are a way for sentient beings to skirt liability. A corporation cannot go to prison for life. A corporation is designed with the goal of producing profit for its sentient owners/shareholders. It has no interest in leading a "healthy" life, only a profitable life.
A corporation can be put to death, and with no due process. See e.g. Arthur Anderson, which was eventually exonerated by the Supreme Court. But long after it was dead.
And that threat can get them to do crazy things, e.g. that's what wrecked AIG a few years before the financial crisis.
Maybe they're something even more than sentient, just like a brain is more than its neurons.