Cell comes from celle as used in modern english and old frisian, or cella in Latin. it means a small room.

    Cell is a small room, a cubical, as in a convent or a prison. Long time ago, cell is a convent or monastery attached to a larger one. Sometimes, the people in the old days used cell to describe a hermit’s hut. Later, people began to use the term to describe a very small hollow cavity or compartment. After the rise of surgery, they call any very small natural cavity in the body a cell.

    Engineers also call the hollow space between the ribs of the vaulted roof the cell. The sociologists use this term cell to describe any group within a large organization whose purpose is to propagandize. In electro chemistry, cell is any compartment of a storage battery. Also cell describes a receptacle containing electrodes and electrolyte used either for generating electricity by chemical reactions or for decomposing compounds by electrolysis.

    In biology, cell is defined as a very small unit of protoplasm, usually with a nucleus and an enclosing membrane. All plants and animals are made up of one or more cells. In botany, cell is any compartment of an ovary, a pollen sac or a spore sac. In zoology, cell is a cup-like cavity enclosing a zooids of certain hydroids, as in corals. In arthropods, cell is the protective covering for the eggs or young of insects, or it is one of the spaces outlined by the veins in the wing of an insect.

    Here, we will only write about cell in the biology field. This is because cell is a basic form of life and in biology we study life, so it is important to learn more about cells. It is not accepted as life by many people outside of science just because it is invisible and so small. Biologists see it as a small basic unit of life. When an organism is made, it is composed of millions of cells. Cell can function alone and it can also function with other same or different cells in a body. This is why it is so important to know and learn what these cells are doing or living in our bodies. Here in this section, the term we refers to all living organisms. Cells are different but here we will concentrate in describing a general cell with common characteristics found across many different cells. However, we will talk about two different general cells, plant and animal cells.

    The question is how did it form. How did the first cell arise? How did the chemicals in the primordial materials on the primitive earth combine to become organic materials? How did the organic materials interact and find the right fit for becoming a tiny body - cell? Logically, the first elements were from the space. Were they only from cooling down earth or were they also come into earth from other bodies in the space? Why there are the physical phenomena such as interaction in the space? Why there are bodies in the space and why there is a space? The fact that all these things are there make more different things. Cell is one of the things that are made from existing materials but it is different because it can make another cell of itself. The first cell or cells appear to come from compounds and elements but later this tiny cell gain property to make itself more and more. Now, how did that happen? After millions of years, the cells even get better at making itself and it does not satisfy. They try new methods of making more of them by mating with other cells and make this time more cells that are different from self. Why do they do that?

    Moreover, the cells are greedy and insecure, so they stay together in groups and we call each group a tissue. A tissue is nothing but a group of cells living together and doing some functions in a body. Why do they combine? Do they talk each other? Do they know each other? We can think they do all of that but in chemical and physical languages. This is not it, there are more, cells in groups the tissues form organ such as a liver or a heart. An organ does a specific work and it also communicate with other organs in a body. This way of doing things is the same from cells, tissues, to organs. Why is it the same? We as individual organism also do the same thing - we do our work and we communicate with other individuals in a community. This is exactly how cells stay and do things in the body. So, we can deduce we behave just like cells. They are our old old ancestors and they are very powerful because we are made of them.

    In medical and health sciences field, we study a lot about cells but in a bigger dimension of cells. In biotechnology, we study many things about cells but in smaller dimension including manipulations within the cells. In biochemistry, we study about cells but concentrate in structures and functions of stuff in the cells. In biology, we study the basics of cells. In genetics, we study the core constituent of cell - genes. In molecular biology, we study molecules in the cells. So there are so many things about cells to study and there are many jobs to do. It is like learning about self in many different ways. We learn who we are, socially, then physically, mentally, behaviorally, physiologically, and we also learn what we are made of and what processes are going on inside of us. This is kind of like learning all about self so we can live a little bit longer and we can live healthier or we can do the reverse of that to those we don’t get along in the context of life such as viruses, or any enemy that can destroy us. We do the same thing on learning about other living things and the environment so we can secure food, shelter, and water.

    If we think about a cell, the first idea that might come into our minds is that it is a sort of an oval ish sac. So there is a body of cell. The cell has boundary that separates the inner stuff from the environment. Without that covering, a cell would not be a cell. To be a cell, it needs a covering. This covering is called a membrane. Now, this membrane is not a solid membrane because it can never be solid because a cell needs to communicate the outside environment. If the membrane is solid, it would be difficult for a cell to get things in and out. Just like us, cells eat foods, and eliminate unwanted stuff. So, the membrane is permeable but not totally permeable. Cell is smart just like us, it will eat only that makes sense to its body. We eat food and we don’t eat plastic. Cells eat food and the food is in compound forms or chemical forms. The cells eat the chemicals that are useful to them. So, the membrane is selectively permeable. Since there is communication between the cell and the environment, the cell body is composed of continuously different and new things. It is like just come and go. None of the things stay inside of the cells permanently. The things are not organelles of the cell but the stuff that make up these organelles of the cells and the cell itself.

    This is the most important part we need to know about structure made of chemicals or elements. Suppose there is a chemical molecule such as CO2 - carbon dioxide in the air, now the C and two O atoms are constantly replaced with other available C and O atoms, based on how many CO2 and other molecules are around that particular CO2 we are looking at. The C in one moment could be exchanged with C from other molecule based on the strength of the interaction. These collisions or interactions are happening all the time. they are so fast and so small that we cannot see them. The point is the components of CO2 or any chemical structure regardless of how complex it is, the individual parts in the chemical structure are interchangeable with the same chemical from the environment.

    Even complex organism like us human, the structures inside of us are made of chemicals and the atoms that make up these chemicals are replenished all the time. We get these raw atoms from the break down of foods and drinks we take in or air we breathe in. That is why living things are not permanent and we age as time goes by. After the growth stage to full adult body, the maintaining of the body depends on the stuff we take into the body. The chemical replenishing process is going on at the same time. If you put it too fast and too much, the replenishing processes in your body get some problem to catch up. They system does not know what to do with the extra stuff and errors can happen a lot in the body processes. Therefore, balance is very important because the body seeks perfection in doing things and it expects you to input the right amount so that it can handle the processes and do the replenishing of chemicals to maintain the structures in the body at the right shape. Sometimes, it is beyond our control because the processes could act wrong based on the genes you are born with such as genetic diseases or bad stuff you do to your body such as smoking. Cancer is one of the process that can happen because of your natural or artificial defected genes. You can see with your eyes the tumor grows because the growth of cell cannot be turned off.

    The point is none of the chemicals composing our body structures is the same at all times and they are recycling with the chemicals in the environment through daily processes we do like eating, breathing, etc. Cells are the units that make us. They also do this recycling of chemicals through eating, drinking, and breathing, etc. What a cell can do is called a property and what a cell has is its characteristic. We will learn all of that about cell in two different versions - plant and animal version of cell.

Selectively Permeable