Indispensible to Life
Natural sugars are unknown to most of the general population. When sugar comes to mind, table sugar, or sucrose, is what normal people think of. it's one of the refined sugars that we would be better off to avoid entirely but it's still better than using artificial sweeteners or high fructose corn syrup.
In actuality, there are hundreds of sugars that occur naturally in nature and several of them now appear on our supermarket shelves and are great, healthier alternatives to the artificial, refined sweeteners; more on those later.
Sugars are the most abundant biological molecules in nature. While most people think of sugars as something to make our food and drinks sweet, many natural sugars or dietary sugars are indespensible to all life.
Functions of Natural Sugars
Some of the more vital functions that natural sugars and starches (carbohydrates) perform are storing and transporting energy and providing the building materials to construct the scaffolding that forms the supporting structure of cells.
They also play major roles in the working of our immune system, fertilization in the reproductive system, clotting of blood as well as determining our blood type.
Even the fundamental ‘codes’ of life (DNA and RNA) are carbohydrate-based chains of recurring molecules called polymers.
By now most people know about genes and our efforts to classify all the genes of the body into a collection called the genome.
Functional Glycomics: Methods and Protocols (Methods in Molecular Biology)
Likewise, there is an ongoing effort in many scientific circles to map the sugar chains into a glycome, analagous to the genome.
This body of science has become known as Glycomics with an attendant area of study called glycobiology, or the study of the role of sugars in life.
Judging by the number and depth of the scientific books now available, Glycomics and Glycobiology appear to be shaping up as one of those breakthrough areas of research.
A few titles are shown here with links to Amazon.com for more information or ordering.
Handbook of Glycomics
Many of the roles that nature has assigned to natural sugars are truly awesome. In our bodies, nature uses certain sugars combined with a protein backbone, called a glycoprotein, to perform guard duty.
As sentrys, their job is to recognize suspect cells such as mutations, bacteria, viruses, toxins and mark them for destruction by our immune system.
To say it another way, carbohydrate structures on the cell surface enable the cell to differentiate between resident cells that belong and illegal alien cells that don't.
In scientific language, a researcher might say something to the effect that "it is carbohydrate structures that act as signal or recognition markers to mediate cell-to-cell recognition, cell-to-cell adhesion and molecular targeting".
Interestingly, scientists have noted that in the presence of inflammatory diseases, infections and the development of malignant cancers, changes occur in the glycoforms, the carbohydrate structure on the cell surface.
Introduction to Glycobiology
The changes affect the physical, chemical and biological properties of the cell surface glycoproteins which in turn have dramatic effects on all the functions of the cell.
Glycoforms were mentioned in the preceeding paragraph and another name for them is glycoconjugates. They are simply a protein or lipid (fat) with various bioactive sugars attached.
Most such glycoconjugates have molecules of the sugars mannose, fucose, xylose or five others attached.
These eight sugars are bio-active sugars, or essential sugars, and numerous books have been written on their attributes and implications for proper bodily function.
Cellular Manipulation of Natural Sugars
The construction of glycoconjugates occurs deep within the cell in an internal structure known as the endoplasmic reticulum or ER for short.
The ER is the cellular assembly line for glycoconjugates and once the structure is built it is shuttled off to another internal structure known as the golgi appartus. The golgi appartus is the cells postal system or distribution system.
The completed glycoforms (glycoconjugates) then penetrate the cellular membrane and take the appearance of a forest of hairs or cilli on the cell surface.
Here the glycoforms communicate with other cells and the transmitted messages can alter the biosynthesis, stability, localization, trafficking, action, and turnover of the molecules comprising the total organism. These processes are also covered in great detail in the glyconnutrient pages linked above.
For this reason, glycobiology and carbohydrate chemistry have gained increasing importance in modern biotechnology.
Many major universities have established huge departments devoted to glycobiology and so far, this is the source of most discoveries in the roles of natural sugars on life.
Several pharmaceutical firms are now devoting a considerable amount of time and money to studying sugars in the hope of finding ways to incorporated their characteristics into new sugar-based drugs; patentable of course.
The practical application of such research into how biological interactions and functions are affected by glycans (sugar structures) will hopefully lead to a way to manipulate them in the human body.
It is encouraging that several human diseases are characterized by changes in glycan biosynthesis which is a driving force in the search for new tools in diagnostics and/or therapeutic applications.
"Glycan" may be a new word to many readers, so let's clarify that glycans are composed of multiple linked sugars and are essential structural components of living cells and a source of energy for animals.
The diverse biological functions attributed to glycans can be grouped into two general classes: (1) structural modulation and (2)recognition.
As modulators, the glycans impart intelligence to the molecule to which they are attached and thus facilitate changes to the molecule. In the recognition role, glycans are recognized by carbohydrate-binding proteins called lectins.
Glycans are widely distributed in nature and, as previously mentioned, their study has become one of the more rapidly growing fields in the biomedical sciences, with relevance to basic research, biomedicine, and biotechnology.
The field ranges from the chemistry of carbohydrates and the enzymology of glycan-modifying proteins to the functions of glycans in complex biological systems, and their manipulation by a variety of techniques.
Research in glycobiology requires a foundation not only in the nomenclature, biosynthesis, structure, chemical synthesis, and functions of complex glycans, but also in the general disciplines of molecular genetics, cellular biology, physiology, and protein chemistry.
Currently the "bible" on the subject is a very large tome called "Essentials of Glycobiology" by numerous authors; Varki, Cummings, Esko, Freeze, Hart and Etzler, all pioneers and giants in this emerging field.
It is a massive work, spanning 51 chapters and over 700 pages and would be hard, if not impossible, to find a more comprehensive coverage of the science of glycobiology.
Essentials of Glycobiology, Second Edition
The book is available from Amazon.com and clicking on the link above or the book's cover will take you there.
If anyone still thinks sugars are unimportant to life, consider that in natural sugar conjugates, the portion of the molecule comprising the sugar, can vary greatly, from being very minor in amount to being the dominant component.
It is striking that sugar chains make up a substantial portion of the mass of most glycoconjugates.
Thus it is observed that the surfaces of most types of cells are covered with a dense coating of sugars, the glycoforms or glycoconjugates introduced above.
The term that describes how newly synthesized proteins originating from the ER (endoplasmic reticulum) are modified with sugar chains is called "glycosylation".
Most glycosylation reactions utilize activated forms of monosaccharides that are catalyzed, or enabled, by enzymes called glycosyltransferases. It appears that most observed changes in sugar structures in the body are enabled by enzymes.
A huge amount of research has gone into understanding the mechanisms of glycosylation and it is clear that a variety of factors determine the final outcome of glycosylation reactions.
Like all components of living cells, glycans are constantly being created and broken down (degraded). Enzymes take care of the sugar chain degradation by cutting the chain at either end.
Then it is possible to remove the cut piece and re-attach a different section of chain without disturbing the underlying main body of the structure.
Sugar structures are almost never straight-line chains but rather have numerous branching chains, like limbs of a tree.
It happens that defects in the construction, or biosynthesis, of the sugar structure often produce a variety of mutant glycoforms which have provided a large body of knowledge into the pathways that biosynthesis can take.
So it is no wonder that many companies are trying to learn how to create pharmaceuticals based on the science of glycobiology. Will they be successful? Probably, but it seems like a waste of energy since the bioactive natural sugars are readily available in whole food and supplement forms.
Just take them and let the cells internal machinery do the work; but then again, you can't patent natural sugars or a natural function of our cells.
In addition, whatever sugar-based drugs that the pharmaceutical companies come up with is sure to be at least ten years away and will be very expensive.
It could be very instructive to leave the science of natural sugars and look at the world of artificial sweeteners or unnatural sugars.
But first, putting all the science aside, very often we hear that fruit is loaded with sugar and should be avoided. It's pure myth and the Discover Good site puts it to rest. Eat your fruit and prosper.
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