The Cell in Brief
The Cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as bacteria, are unicellular (consist of a single Cell). Other organisms, such as humans, are multicellular.
Humans have about 100 trillion or 1014 Cells; a typical Cell size is 10 µm and a typical Cell mass is 1 nanogram. The largest Cells are about 135 µm in the anterior horn in the spinal cord while granule Cells in the cerebellum, the smallest, can be some 4 µm and the longest Cell can reach from the toe to the lower brain stem (Pseudounipolar Cells). The largest known Cells are unfertilised ostrich egg Cells which weigh 3.3 pounds.
All Cells have a 'skin', called the plasma membrane, protecting it from the outside environment. The Cell membrane regulates the movement of water, nutrients and wastes into and out of the Cell. Inside of the Cell membrane are the working parts of the Cell. At the center of the Cell is the Cell nucleus. The Cell nucleus contains the Cell's DNA, the genetic code that coordinates protein synthesis. In addition to the nucleus, there are many organelles inside of the Cell - small structures that help carry out the day-to-day operations of the Cell.
http://en.wikipedia.org/wiki/Cell_(biology) & web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm
Illustration 1 shows the division of the Cell in a simple, phase-by-phase manner, whereby the Cell splits itself up into two. As soon as these divided Cells grow as big as its “mother,” they in turn repeat the splitting-up phase, thus more new Cells appear. The process of dividing goes on and on as long as adequate resources exist.
As cells today appear in a great variety of types, we shall here talk more about the type of Cell known as the Eukaryote Cell and one that does the splitting only Mitotically. Although the Prokaryote Cell is said to be the one that emerged the earliest, in this book however only a glimpse of it is given.
Let’s now take a look at the uniqueness of the unicellular creatures or the single-Celled living creatures.
Man of the past had generally had the opinion that all living creatures must, sooner or later, die. Such an opinion had stemmed from the fact that in those days the microscope had not been invented yet, which had led him to think that nothing else, apart from what he could see with his bare eyes, could possibly have been in existence. Thus, the living creatures he meant were confined to only the ones visible to his bare eyes. Basically, those creatures the early man had been referring to were creatures that—like us, animals, and plants—had evolved from the combination of a great variety of Cells and the ones that could experience death. It was not until after the invention of the microscope that man has come to realize the presence of multitudes of other living creatures too small to be visible to his bare eyes. They soon came to realize too that these living creatures reproduce themselves not by conceiving their offspring nor do they do it by laying eggs and then hatching them. Rather they multiply by splitting themselves up. What is unique about these self-splitting creatures is that their life process is continuous.
The diagram above shows how a monocellular creature splits itself from time to time.
As is illustrated in the diagram, we may then infer that a monocellular creature that still survives until today has never had its life process ended since the time it first appeared in the World billions of years ago. All it has undergone is a change in its bodily shape as well as in its body’s composition, due to the billions of years of influence by the various external forces exerted on it. Therefore, the claim that all living creatures must experience death is one that still needs to be thoroughly proven (illustration 2). In fact, some of the simpler animal organisms are biologically immortal, such as the hydra or the jellyfish Turritopsis nutricula. Yet it will always be different from a unicellular, whose immortality is more obvious.
What an amazing phenomenon indeed!
To further clarify the explanations, above is an illustration of the development of unicellulars, multicellulars (Turritopsis Nutricula and Hydra), and Human-beings.
These three life forms have each its own uniqueness. Turriptosis nutricula and Hydra are said to be biologically immortal. Yet if one is to take a look at both these living creatures, there is just no way by which one can tell that the ones that have managed to stay alive until today are the ones whose life process have continued to last since the time they first came into being and have since then never experienced death yet. Who knows! The ones that are still alive till today could have been born of an egg or a zygote. As for Turriptosis and Hydra, biologically immortal though they are said to be, because of their ability to replace/fix their damaged bodily cells, they are yet subject to death in their evolutionary journey, perhaps by some disease or by being preyed upon by some other animals. The possibility of their being able to survive for billions of years till today has not been proven yet. This is very much different from the unicellulars, which still live until today—as they are known to give birth to their “offsprings” by dividing themselves, it can then be said for certain that the life process they get from such division is a never-ending one.
As for man, however, while it is true that his gamete cell can survive till today, he is yet mortal, as death must always befall any multicellulars that take the form of man.
Unicellulars and multicellulars (mortal like us) are different from each other—although in fact long before multicellulars are what they are today, they were but mere combinations of unicellulars. Unsurprisingly though, once the unicellulars combine with each other to form multicellulars during that period (the Proterozoikum period), they find it very difficult to become independent. This is because the instant they combine, they begin to adapt themselves to their new being: a shift occurs in their lifestyle, i.e. from one that was individualistic to one that is communal. They have to adapt themselves to their new life condition, where they have to live in togetherness and in unity as multicellulars. Accordingly, there occurs some sort of a division of labor among those unicellulars, now that they are living in togetherness as a multicellular, in regulating the process of metabolism. The communal cells in the multicellulars existing today, unlike the unicellular of a bacterium, are void of the ability to undertake the process of metabolism on its own.
Nonetheless, it is this unique characteristic of the unicellulars that has been the very reason why the human, animal, and plant species survive till today. These unicellulars are capable of not only dividing themselves but also replacing their dead Cells. With the unicellulars being able to divide themselves, the multicellulars formed by the union of the various unicellulars naturally grow bigger. What’s more, the gamete present inside one multicellular creature has the ability to merge with the gamete of another multicellular creature, thus resulting in the emergence of a new multicellular creature. Though multicellulars as individuals are short-lived, the ability of the unicellulars to stay alive for a very long time may lead to the longevity of human, animal, and plant species.
That is why the Cell, which is claimed by many as the source of life, has always been an issue of greatest concern, particularly as concerns how it first emerged on this earth.
Where does the Cell come from?
Does it come from everything that we have in nature?
Is it not God who has created all the basic materials that make up the entire content of the Universe, including human beings?
Do the basic materials, such as atoms, not have immense power in it and do they not have the incredibly tremendous speed required for the formation of the contents of the Universe, including human beings? Is it not to be acknowledged that even until today the development of the various space objects continues?