As a somatic educator I am leery about analogies to the cell. For example, it's popular to imagine that the movements of breathing, a contraction and expansion of the rib cage are echoed at the cellular level, but it's simply not an apt analogy. Oxygen gas is a small molecule that moves at the speed of sound, and it simply doesn't get squeezed or sucked into cells. We can watch cells with a microscope. They simply don’t have respiratory movements.
As previously explored, it's occasionally useful to think of cells as complicated machines, especially to discover the limitations of such thinking. So please imagine a completely automated phone factory. Raw materials go into one end of the factory, manufactured and packaged phones come out the other end, ready for shipping. As long as the input materials are available, the phones are continuously manufactured.
A moment's consideration will show that the input materials contain not-only the constituents of the manufactured phones, but the constituents of the factory itself. As the factory ages it needs all kinds of replacement parts and these must also be fabricated inside the factory. These maintenance tasks apply not only to the machinery of phone-crafting but also the structural integrity of the factory itself.
As well, the factory needs energy to operate and this also must come from outside. So imagine your energy source of choice included in the input materials. Here I usually imagine an endless supply of potatoes but we all have our own picture of an energy supply of one kind or another. However the energy is stored or transmitted, it must come from outside the factory.
This factory is like a cell in many aspects. The "life processes" culminate in the operations and maintenance of the factory. One could tell, from comparing the exquisitely rich complexity of the phones to the relative simplicity of the input materials, that some tremendous wisdom or knowledge was required to accomplish the manufacturing process.
No factory yet built can accomplish the above tasks, and note that our factory does not grow, develop, or reproduce, but merely operates and maintains itself. I think growth or reproduction are necessary characteristics of terrestrial life, and perhaps of evolved life, but not necessarily required for satisfying the philosophical criteria of being alive. So a cell is considerably more impressive than our self-running factory! But an artificial organism, one that was not evolved but designed, would not necessarily grow or reproduce, like our factory.
Our factory runs itself. All of the tricks of the trade -- metallurgy, fabricating electronic parts, assembly -- are built-in. If the factory doesn't know how to make something (like an atom of copper) then it must be supplied in the input materials. This is a fancy factory, but a version of ones that actually exist.
But our factory also maintains its own form; it can make all of its own replacement parts. The terms for this is autopoiesis. Although the origin of our factory is unknown, the actual structure of the factory itself is also a product of the factory's activities. The factory makes and replaces its own roof, walls, and doors. The factory, as a discrete object, is also self-maintained. We have not yet encountered in real life such an artifice as our autopoietic factory.
Still, an autopoietic phone factory is missing a key aspect of living systems. If the input materials are always provided in the same quantities and proportions, and the same phone is always manufactured, then the factory will run indefinitely. But imagine one input material (say, copper) is replaced with another one (say, silver). Silver can replace copper in most applications, but the details of how it's used will change because it has different properties. For example, a silver wire can perform the same as a copper wire while being narrower, because silver is a better conductor of electricity. So if the factory is 'fed' a different input metal (extra silver, no copper) perhaps it could keep making the same phones, but it would have to change its manufacturing recipe.
This ability to sense a change in the input materials, and to adjust behavior in order to accomplish a desired result, seems essential to describing our factory as alive. Otherwise, it's just a fancy robot, automatically doing the same thing over and over. As the local conditions around an organism are always fluctuating, no living thing could endure without being adaptable to those fluctuations.
If we add that ability to our factory -- some system for interpreting the varying types of input materials and then adjusting the manufacturing process, then it acts like a cell in the non-reproductive phase of its existence. That's why the cell's like a fisherman.
Without this ability to sense what's available in the outside world, and then to respond, this is my course of action, there is no living factory. Consider how a device for detecting whether a chunk of metal was copper or silver would need to convey a message to the rest of the factory. The message isn't just a label, "this chunk is silver" or "this chunk is copper" but rather something like, "90% of chunks in the last hour are silver" because the behavior of the whole factory needs to cohere with the nature of the input materials.
Just like a fisherman, the factory "goes out" into a world with uncertain and varying availability of the raw materials. If no suitable materials are found, no phones are made. If there are no fish, no fish-hunting can occur. The actions of the fisherman will change, based on the actual situation they are in.
The fisherman cannot directly perceive where the fish are. The outside world is only partially predictable. All of the fancy sonar technologies, meteorological data, and fishing gear cannot directly furnish fish. No matter how intelligently the task is executed, a fisherman places nets or lines in the water, and fish wind up caught or free. Even if one locates a large school of fish, and deliberately moves a large net towards it, the details of which fish get caught are much more up to the fish than the fisherman.
A cell can only fish for its living. That's because all cells move their materials in and out through diffusion processes. Even when a cell is very actively doing something, it's completely beholden to diffusion processes. For example, the sodium-potassium pump uses an energy source to move sodium outside the cell and potassium inside. Sure, once a pump has 3 sodium ions bound on the inside of the cell, and 2 potassium ions outside, it's in a position to move the ions against their diffusion gradient. But the 3 sodiums and 2 potassiums only find their binding sites on the pump from passive diffusion. The cell passively fishes for the right ions and then actively moves them around.
As useful as it may be to think of cells as miraculous, self-maintaining, self-operating factories, the biggest trick they do is changing their strategies depending on the available opportunities. Working with billions of years of accumulated wisdom, cells constantly sense their surroundings and prepare for the next fish to bite.