A Stab at Life

I was running a couple days ago and here is what I came up with. I decided at some point in the course of things that for whatever reason I was going to try and define life, something that still pesters science.

So here goes:
As of this moment my attempt at defining life has two parts.
1) The entity must be able to collect energy is some fashion and store it in a physical structure that can be broken down and released later.
2) The entity must be able to replicate.

Now in the first part of the definition what one must pay attention to is the storing of energy in a physical structure. It is not sufficient for an entity to absorb and re-emit energy, essentially every bit of matter can do this in some capacity, that doesn't mean it is alive. No, to be alive an entity must take energy and convert it into a form that it can not only use for its own ends, but more importantly store for later use. Since the only way we will know that the entity has stored this energy is if it creates some physical structure, a chemical bond of some form or even perhaps more exotically in some mechanical fashion I'll not limit the physical form it takes, that has some energy potential.

One might notice that I do not require that the organism be able to release this energy again once it is stored. I conceive of the possibility of a symbiotic relationship existing between two entities whereby the entity storing the energy is only able to release it with the aid of the second entity.

The second part of the definition is the reason a wind turbine is not alive. A wind turbine can take energy and store it is a physical form, but it is incapable of replication. There is no conceivable scenario in which a wind turbine creates another wind turbine.

Before we move on to the difficulties of this position let me first answer the question which may occur to some: Does an entity need to be able to replicate independent of any other entity? Clearly our experience tells us no, an entity may need another entity (of say, the opposite sex), and expanding past our, or at least my experience, it is also permissible for an entity to require a chemical, or object to replicate.

Now stepping gingerly out into the brush Does an entity need to replicate an exact copy of itself? Again, our experience tells us no, it doesn't. To this point, so long as the product of the replication does itself fulfill the criteria above for being alive it is permissable to call the original entity (entities) alive.

Here we have reached the truly daunting terrain: How does one define an entity? Humans, who are alive, are composed of trillions of live cells. These cells are alive yes, they take energy in and store it in physical structures, and they replicate all the time. However, while they themselves are alive they are alive in service of a greater entity, the person. But what is the difference between the living cells of my lungs which are part of me, and the bacterial cells in my gut which are alive but not a part of me? To this I have no answer which is disappointing since in writing this I had talked myself into really believing this two part definition I had dreamed up.