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THE LANGUAGE OF THE CELL MAY 3 rd, 1996 SCIENCE 10 AP BOOK INFORMATION LIBRARY: Fish Creek Area Library NAME OF BOOK: The Language of the Cell AUTHOR: Claude Korean PUBLISHER: McGraw-Hill, Inc. PUBLICATION DATE: 1993 CALL NUMBER: 3 9065 03969 1246 DUE DATE: May 3 rd, 1996 The cell is a complex and delicate system: It can be seen that the cell is the stage where everyday functions such as molecule movement, protein synthesis and tissue repair take place. All organelles within the cell are well rehearsed in their operations, but an error on an organelles behalf, can send the cell and it s organelles into panic. The efficiency rate of the cell plummets down to a low level. It does take some time for the dust to settle, and once the scripts are memorized, the cell is now ready to begin it s tasks again.
Since the 19 th Century, it was known that all living things, whether they were plants or animals, were made up of cells. This whole idea has been given credit to an English Physicist, Robert Hook (1635 - 1703), when he looked at a thin slice of cork under powerful hand lens. Hook discovered a large number of cells. Rudolf Virchow (1821 - 1902) propounded this idea, that the cell is a basic structure and functional unit for all living organisms. A cell can be a wide range of shapes and sizes, although most cells are microscopic. Inside a cell membrane, a nucleus can be seen.
The nucleus is the control center of the cell. Between the nucleus and the membrane, there is a polysaccharide matrix called the cytoplasm, where organelles can be found. The organelles are attached to a framework. The cell s cytoskeleton.
Every living cell has the ability to detect signals from it s environment. The signals are usually in the form of chemical molecules, that the cell has learned to recognize. The cell decodes these molecules into messages, and acts upon them. The cell has a language. Signals and messages are carried by particles of matter that have a very low energy requirements.
There are many, many signals rumbling around the cell. It was thought that the cell would confuse itself in all of that background signal noise. One defense is available to this question. The cell s decoding mechanisms are located downstream from the receptors. They are based on complex chemical reactions that take place in the cell membrane and control all the responses of the cell to the messages it receives. Neuropeptides and polypeptide hormones, are made up of complex assemblies of amino acids, aligned in different sequences.
In other cases, the amino acids are slightly transformed, as this is the case with well known transmitter substances such as epinephrine (adrenaline), dopamine and histamine. Products made in the organelles within the cell, are sent to various destinations, both in and out of the cell. The cell has what amounts to a parcel delivery service, that is guided by addresses, by chemical tags or labels. These labels generally consist of fairly simple molecules (often sugars) attached to the product being forwarded and recognized by the structure for which it is intended. When a cell messes up on a delivery, which doesn t happen very often, is usually the result of a genetic defect.
The tag on the product being forwarded is usually mutated, therefore the receptor cannot recognize it. Sometimes, the receptor is mutated, meaning that it does not recognize the signal. The result of this is a botched cell. An example of this is a low density lipoprotein receptor. If the lipoprotein fails to sequester and internalize it s signal (cholesterol), then cholesterol can no longer be reincorporated in the cell, and it builds up in vessels, causing potentially fatal conditions. Three recent discoveries about the cell tell us that; A) Each cell is not simply controlled by an accelerator and an inhibitor, and the cell has the ability to recognize a great amount of signals.
B) The number of signals discovered in the body has increased tremendously. C) Signals within the cell are not, as formerly believed, characteristic of an organ or function, but they are all found in nearly all organs and are associated with nearly all functions. As mentioned earlier, signals are incredibly small, have low energy requirements and weigh approximately one billionth of a gram. Scientists have discovered new signals with the development of extremely effective chemical methods that make it possible to purify them and elucidate their structure. These advances and discoveries lead to a well understood field of protein chemistry. One problem is that new signals are coming out everyday point which should be stressed is that the universality of communication implies that no signals are attached exclusively to one organ or function.
However, signals do not circulate unrestrictedly throughout the body. Most signals are very versatile in the way that they can carry out all sorts of assignments whether it be local cell to cell communications or long distance cell to cell communications. The best example of this is epinephrine, which acts both as a nervous system mediator and as a hormone. On the contrary, some signals remain highly specialized, and therefore cannot take on many of the tasks that a versatile signal can. GnRH, a small peptide of amino acids, is mainly involved in the regulation of sexual behavior, reproductive hormones and external genital organs. These highly specialized organs can be found in a select amount of organs only.
All cell s and organs depend heavily on the receptors and decoders ability to do their job. Recognition errors by the mechanisms in the immune system can have grave consequences: unintentional destruction of elements of the self, failure to be alert to nonself antigens. The cells responsible for the body s defenses use different decoding combinations for protection. Example is that a foreign antigen is perceived foreign only if it is presented to the lymphocyte (white blood cell formed in lymphoid tissue) by another cell.
The cell s crash-free system calls for one more security check. Appropriate signals have to confirm the order to respond to the intruding antigen by the secretion of antibodies. Fail safe? The reader definitely hopes so. Neuroendocrinolgy.
A nice long name for an extremely important field of study. Neuroendocrinology is the study of the exchanges of signals, and how they are integrated in the general coordination plan of an organ. A cooling of the outside temperature perceived by the nervous system s sensory organs triggers an increase the production of heat and at the same time a decrease in it s dissipation. The same goes for when it is hot outside, the sensory organs order a decrease in heat production and the dissipation rate is raised. The steps the cell go through, are similar to that of the thermostat. Both responses involve concomitantly nervous mechanisms (changes in behavior, chilling, etc) and a hormonal link; stimulation of the thyroid.
This is an example of a neuroendocrine reflex. It is interesting to note how a thermostat can be related to a neuroendocrine reflex. Home device ideas taken from bodily functions may turn out to be a useful tool in the school curriculum. Students could relate various abstract concepts to everyday household devices.
Their is an old question of the relation between the simplicity and complexity in biology. During the course of evolution, rules about the theory of cell communication has more or less remained unchanged. A primitive organism; a bacterium or an amoeba, when directly immersed in a liquid medium, fulfill the need for securing information regarding their environment. What are the available nutrients? The unicellular organism decodes this information and acts upon it. If their are food signals, then the amoeba will undergo phagocytosis, capture the food and then enzymes will be released and the food will be digested.
The cell and it s signals is a continuing circle. The reader thought that the Language of the Cell was an extremely hard, well written book. The book went deep into the subject most of the time, and sometimes the reader found this confusing. One negative point discovered by the reader was that the concepts explored in the book were new, confusing and frustrating. Little was understood on neurology, yet the reader made an incredible effort in trying to understand, and make sense of the topic. The reader feels that there are not many books that have to deal with biology on a grade ten AP level.
Therefore, a reading assignment of this sort can be extremely challenging, and leave the reader with too many questions and no answers. The reader feels that these kind of book report assignments should be explored in grade twelve, when DNA and other neurological concepts of some sort are known. The reader felt that this whole book report was an experience, and it broadened the reader s knowledge base. The reader also found out that biology is a very interesting subject as a whole, but some fields of study under the whole biology picture are extremely boring and complicated. Maybe this impression will change over time.
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