Unveiling the Human Cell: Structure and Function

History

One of the most significant discoveries of the 19th century was the "Cell Theory." This theory was introduced by two German researchers: a botanist named Matthias Schleiden (Schleiden) and a physiologist and zoologist named Theodor Schwann (Schwann). The theory essentially posits that all living organisms are composed of cells (Cells). At the time Schleiden and Schwann presented their theory to the scientific world, the immense complexity of living cells was not yet understood. Thus, archaic theories about the spontaneous generation of life forms were still prevalent.

Twenty years later, a German scientist and anthropologist named Rudolf Virchow (Virchow) expanded on the cell theory, asserting that cells do not spontaneously arise but rather emerge only from pre-existing cells. He is credited with the famous Latin phrase: "Omnis cellula e cellula," meaning – all cells (or every cell) originate only from another cell.

"Scientific research over the past few decades has accumulated extensive scientific knowledge about the common principles that apply to all cells, whether a plant cell, a bird cell, a mammal cell, or a bacterial cell. It is now known that cells and their genetic material replicate in a manner that passes on the correct amount of material to offspring, in a uniform way – similar methods are utilized for energy creation and usage." (Prof. Yehuda Ben Shaul, The Living Cell – Structure and Function, Open University Press, p. 10).

What is a Cell?

Cell Structure and Function

Scientific research today reveals the highly complex structure of the cell and its various functions: nerve cells, muscle cells, etc. Here are some more detailed examples of cell functions and structures:

* Nerve Cell (Neuron): "It is a long, branched cell, and its structure perfectly matches its functions of receiving instructions and conducting responses. Humans respond to touch, wind, a hit, a sting, and so on – through nerve cells." (Prof. Yehuda Ben Shaul, The Living Cell – Structure and Function, Open University Press, p. 10).

* Muscle Cell: A single cell within the cellular system, operating in a very organized way, assisting in muscle construction and contraction.

* Membrane (Cell membrane): "All cells are bounded by a membrane. This membrane has selective permeability, meaning not all substances outside the cell can freely enter the cell. Some materials are allowed access, while others are blocked." (ibid, p. 16).

* D.N.A (Deoxyribonucleic Acid): "This molecule stores hereditary information passed from generation to generation and information for protein synthesis... A DNA molecule is well-suited for information storage. It is filamentous and highly stable. One might compare a DNA molecule to a magnetic tape of a computer or tape recorder. Similarly, in DNA, the information is 'encoded' chemically along the length of the molecule." (ibid, p. 13).

* R.N.A (Ribonucleic acid): "This filamentous molecule has a structure closely related to DNA. RNA molecules carry the information encoded in nuclear DNA to sites outside the nucleus where proteins are synthesized... RNA is created through transcription from DNA, and thus the information sequence in RNA is identical to that in DNA. This process is somewhat similar to copying signals from one magnetic tape (DNA) to another (RNA). However, not all information or signals are transcribed; only the necessary parts. In the cell, only information related to the creation of required proteins is transcribed into RNA at any given time." (ibid, pp. 13 – 14).

* Organizational Level: "This is a feature characterizing all living cells; since cells form the building blocks of complete organisms, this feature characterizes living beings themselves. Organizational level in cells refers to the precise arrangement of various components relative to each other. This compact organization, where the scales are small, is energy-efficient.

When this energy supply is disrupted, due to various reasons, organizational level decreases, and disorder rises. If the replenishment of energy doesn't occur, the cell will die. In other words, living organisms, and the cells composing them, 'adhere' to the laws of thermodynamics." (ibid, p. 11).

Dr. Gil Gershon Tavon, holding degrees in astronomy, astrophysics, and cosmology from the University of Cape Town (U.C.T) in South Africa, explained cell complexity wonderfully, writing: "It is difficult to impart this impression to someone not well-versed in molecular biology. To gain a general impression, consider visualizing a cell magnified a billion times. To the observer, it would appear as a spaceship-like structure, its area large enough to cover a large city like New York. Its walls contain millions of openings that open and close, allowing controlled flow of hundreds of thousands of different types of materials in and out. By entering one of these openings, we find ourselves in a world of fantastical and hair-raising technology. We first notice an almost endless system of tubes, arranged in a maze that is difficult to trace, branching from the exterior surface of the cell to every corner of the cell, reaching the central nucleus and, from there, to the central memory bank, the nucleus, or to assembly and energy plants, etc. The nucleus itself resembles a geodesic sphere about a kilometer in diameter, where kilometers of highly sophisticated spatial DNA molecules are precisely folded. In every direction, we look, we will see almost unlimited numbers of 'robot-like machines.'

In the simplest functional component of the cell – a protein molecule – there exists a "molecular machine" composed of several thousand atoms with precise spatial arrangement crucial for their function.

The functioning of the cell relies on the integrated action of tens of thousands of such molecules (some researchers hypothesize this number is in the hundreds of thousands!), which must operate synchronously, one after the other, during the cell's production cycle.

The cell appears to have every aspect of our sophisticated machine technology likened within it: programming languages, decoding and encryption systems, memory banks for storing and retrieving knowledge, automatic production monitoring systems, quality control and "fail-safe" mechanisms, etc. To our eyes, the cell might seem like a vast factory, as large as a city, performing numerous unique functions akin to all of humanity's production processes combined. However, it possesses one quality unmatched by any human-made factory or machine – the remarkable ability to self-replicate within hours. Nothing can inspire more awe than watching the fantastical process in which every component and part of the cell creates an exact copy, organizing into another virtually identical cell without disrupting the cell's operation (it continues living)... Besides the cell's production systems (consider, for instance, the exquisite taste of pineapple or the fragrance of jasmine, produced in the cell's laboratories far more sophisticated than any modern chemists' imitation labs), the cell solves all the problems of a giant city. Air conditioning, constant temperature, waste material drainage, and primarily energy. Today, scientists are beginning to seriously consider the commercial use of solar energy. Plant cells have already solved the issue of transforming solar energy into chemical energy by creating a complex chemical compound called chlorophyll, which gives leaves their green color and serves as the exclusive source of carbon supply for the animal and plant world. Instead of batteries, the cell stores energy in sugar molecules, breaking them down into their components when necessary, maintaining the carbon cycle and utilizing energy." (Dr. Gil Gershon Tavon, A Different View on Evolution, pp. 35 – 36).