I mean, they are living cells. How/why does that even need to be defined? They are animated, with intrinsic purpose(to continue to live).
Single celled organisms are also alive.
The relevant distinction is not how complex the living organism is/isn't. We kill living things(simple and complex alike) all the time, everyday, and don't consider those actions murder.
The relevant distinction is that the life is human, and killing that life is(should be) categorically(legally) murder.