History and discovery of glucose

A sugar industry existed around the shores of the Mediterranean between A.D. 700-1600. It was founded as part of the Arab agricultural revolution. The first reference of glucose was “grape sugar” in Moorish writing 1100 AD. The Moors introduced sugar to Europe for the first time by bringing sugarcane from the Nile valley. It grew particularly well along the Mediterranean coast and especially in the Málaga area of al-Andalus.

The sweetness of sugarbeets was recorded in 1590 AD. In 1600, the French agronomist Olivier de Serres noted that ‘‘The beet on being cooked yields a syrup which is beautiful to look at on account of its vermillion color’’.

Glucose, a ubiquitous carbon source preferred by most cells, was first identified by German pharmacist, Andreas Marggraf in 1747. In that year he used alcohol to isolated sucrose from sugar beets, arguably his most influential discovery, as it has revolutionized the modern sugar industry with the process, he used to extract such sugar. He identified the sugar beet’s dried, crystallized juice as identical with cane sugar by the use of a microscope.

In the same year, he experimented with raisins to extract glucose. Raisins are comprised of many molecules, including many sugars like sucrose, fructose, and glucose.

The name glucose was coined in 1838 by French chemist Jean Dumas, from the Greek word gleucos, which means ‘sweet’ or ‘sugar,’ and the structure was discovered by Emil Fischer around the turn of the century.

In 1884, Emil Fischer synthesized some of the known sugars such as fructose and glucose, and he identified 16 stereoisomeric forms of glucose.
History and discovery of glucose

The fruit sugar of fructose

Sugars are naturally occurring sweeteners, the most common in our nutrition being sucrose, fructose, and glucose. Fructose and glucose are monosaccharides present in small amounts in fruits and honey.

Fructose is a monosaccharide found in nature primarily in fruits. It’s eaten as sucrose (common table sugar), which is composed of equal parts of glucose and fructose. It is the sweetest of the naturally occurring nutritive (caloric) sweeteners and has many unique functional and nutritional properties that make it a valuable food ingredient. Fructose is a hexose, with a chemical formula C6H12O6 identical to that of glucose.

When fructose is attached to a sugar called glucose, it forms sucrose or ‘table sugar.’ Long chains of fructose are called fructans and are found in certain vegetables, wheat, and other foods.

 Fructose is also found in sucrose (table sugar), honey, agave nectar, fruit juices, fruit juice concentrates, pure crystalline fructose and high fructose corn syrup (HFCS).
The fruit sugar of fructose

Simple sugars or monosaccharides

The two main types of sugars are monosaccharides and disaccharides. Monosaccharides consist of a single sugar molecule.

Monosaccharides may contain from three to nine carbon atoms although most of them contain five or six. A three carbon monosaccharide is called a triose; one containing four carbons is called a tetrose; five, a pentose; six, a hexose; seven, a heptose; eight an octose and nine a nonose.

*Pentoses (Arabinose, ribose, xylose)
The pentose sugars, deoxyribose and ribose, are essential components of the genetic material DNA and RNA. E.g. glucose and fructose: (C6H12O6); arabinose and xylose: (C5H10O5).

Arabinose is found in gums and when several arabinose molecules are joined together, a pentosan formed.

*Hexoses
-Aldohexoses – galactose, glucose
-Ketohexose - fructose
All hexoses have the same chemical formula C6H12O6, but slightly different structures. In nature, only fructose and glucose occur in free form. Galactose joined with glucose forms the disaccharide lactose.

Glucose is a hexose. Octoses and nanoses are quite rare. Glucose, the main source of energy for body cells, is found in most sweet fruits and in blood.
Simple sugars or monosaccharides

Glucose, the simple carbohydrate

A 6-carbon sugar, glucose is one of the simplest carbohydrates found in foods. It is one of the most important carbohydrates in plant and animal metabolism.

The compounds D-glucose or dextrose is 2,3,4,5,6-pnetahydroxyhexaldehayde, or conventionally expressed as C6H12O6 with a molecular weight of 180,6 kDa. Glucose is readily soluble in water in a powder form.

Glucose is also the primary repeating sugar unit of most complex carbohydrates or starch.

While many foods contain traces of glucose, it is found in significant amounts only in fruits, such as grapes.

Photosynthesis converts carbon dioxide and water to glucose, which is stored in leaves, stems, fruits, roots, pods and seeds, as glucose, as other sugars or as starch.

The small, amount of glucose in the blood and cells provides the energy need for human body’s daily activities. Any galactose or fructose that is absorbed into the blood is converted to glucose by enzymes present in the liver.  It is an essential energy source for the adult human brain.

Glucose is stored as glycogen, an α-link polymer, predominantly in the liver and muscles.  On average m a 70 kg man may store 500g of glycogen.
Glucose, the simple carbohydrate

Synthesis of glycogen

The biosynthesis of glycogen in liver and muscle is linked to the nutritional status of the body, as represented directly by blood nutrient levels and individual directly by the concentration of hormones such as insulin, glucagon, catecholamines and glucocorticoids.

Stimulation of glycogen synthesis is one of the major physiological responses modulated by insulin.

The process occurs in the cytosol, and requires energy supplied by ATP and uridine triphosphate (UTP).

The synthesis of glycogen involves at least two distinguishable stages.

First by controlling the uptake and transport of glucose – the building block for the synthesis of glycogen molecule and secondly, by regulating the phosphorylation and activation states of enzymes involved in the synthesis and degradation of glycogen.

Most of the glycogen synthesis occurs through the lengthening of the polysaccharide chains of a preexisting glycogen molecule in which the reducing end of the glycogen is attached to the protein glycogenin. Glycogenin is a protein that attaches short chain of eight glucose molecules to the hydroxyl (-OH) group of a tyrosine residue on itself.

Glycogen synthase is responsible for making the α(1→4) linkages in glycogen.  This enzyme only elongates already existing chains of glucose.
Synthesis of glycogen

Glucose functions in human body

Glucose is a monosaccharide, which is derived from dietary carbohydrates. Glucose is the only simple sugar that is transported in the bloodstream and it is commonly referred to as ‘blood sugar’.

Human body derived the glucose they need primarily from starch, a carbohydrate produce by plants. Glucose is found naturally in fruits, honey, sugarcane, sugar beets sweet potatoes, parsnip, onions and many other vegetables.

In the digestive system, starch is broken down into glucose molecules. Glucose then enters the blood stream.

The body cells use as much glucose as they can for their energy needs of the moment. Excess glucose is linked together and stored as glycogen.

Glycogen is the form in which the body store glucose in the liver and skeletal muscle cells. Glycogen is composed of long, highly branched chains of glucose molecules. When the blood glucose levels fall the human body are able to convert liver glycogen into glucose, which is called glycogenolysis.

To handle the glucose that’s still coming in, body tissues shift to burning more glucose for energy instead of fat. As a result, more fat is left to circulate in the bloodstream until it is picked by the fatty tissues and stored there.

In healthy individuals, a decline in blood glucose is normally prevented by homeostatic mechanisms. Serious problems can result in people whole glucose homeostasis is not operating properly.

A low level of glucose in the blood is called hypoglycemia. And is as harmful to the brain as is lack of oxygen. A high level of glucose in the blood is called hyperglycemia and can lead to glucose in the urine – glycosuria.
Glucose functions in human body

Monosaccharides

Carbohydrates are major functional constituents of living system. Carbohydrates may be classified as monosaccharides, oligosaccharides, and polysaccharides.

Monosaccharides are simple carbohydrates containing between three and eight carbon atoms, but only those with six and five or six carbon atoms are common.

Monosaccharides consist of a single sugar molecule – mono meaning “one” and saccharide “sugar”.

Monosaccharides are often classified by both their number of carbon atoms and their functional group.

For example, an aldohexose is a monosaccharides that contains a total six carbon atoms including that of the aldehydes in its structure. Similarly, a ketopentose has five carbons in its structure including the one in the keto group.

Three of the most important ones in foods are the six carbon sugars glucose, fructose and galactose.

All the three monosaccharides have the same number and kinds of atoms but in different arrangements.

Glucose is known as an aldose sugar because it contains an aldehydes group (CHO) located on the first carbon atom of the chain.

Most cells depend on glucoses for their fuel to some extent, and the cells of the brain and the rest of the nervous system depend exclusively on glucose for their energy.

Fructose is a six carbon sugar, like glucose but it is a ketose sugar, not aldose , because it contains ketone group and not an aldehydes group.

Fructose occurs naturally in fruits, honey, and saps, Other source include soft drinks, ready to eat cereals and other products sweetened with high-fructose-corn-syrup.

Galactose rarely occurs as a monosaccharide in food. It usually chemically bonded to glucose to form lactose the primarily sugar in milk and dairy product.

During digestion galactose is freed as a simple sugar.

Monosaccharides are also often called sugar. Hexose are six-carbon sugars, pentoses five carbon sugar and so on. The word ‘sugar’ associated with ‘sweetness’ and most (but not all) monosaccharides, have a sweet taste.
Monosaccharides

Glycogen

Glycogen
Glycogen is produced in the liver from glucose. And it is stored in the liver, as well as in the muscle where it is available for immediate use as energy.

Both liver and the muscles can store only a limited amount of glycogen; therefore, when an excess of carbohydrates is ingested, there will be a tendency to develop an excess of glycogen.

The excess carbohydrates will then be converted to fat and stored in body as fat.

The body maintains equilibrium between glucose, the energy-producing sugar, and glycogen, which can be converted to glucose as the glucose in the blood used up to produce energy.

The production of energy from glucose involves oxidation of sugar with the release of water and carbon dioxide, which are easily removed from the body.
Glycogen

Carbohydrates: Sugars

Carbohydrates: Sugars
Sugars, important in nutrition, consist of monosaccharides, having the general formula C6H12O6, and disaccharides, having the general formula C12H22O11.

Although the monosaccharides consists of 3-carbon sugars (trioses), 4 carbon sugars (tetroses), 5-carbon sugars (pentoses), and 6-carbon sugars (hexoses), only the latter are important in human nutrition as sources of energy.

Glucose, a 6-carbon sugar, is one of the simplest carbohydrates found in foods. While many foods contain traces of glucose, it is found in significant amounts only in fruits, such as grapes. Fructose, also a 6-carbon sugar, is found in fruits and honey. Both of these sugars can be utilized by the body as a source of energy.

Sucrose (the ordinary table sugar derived from sugar and beets) is a 12-carbon sugar that is broken down in the intestine to glucose and fructose, hence utilized as a source of energy.

Lactose, the 12-carbon sugar present in milk, is broken down in the intestine to glucose and galactose (6-carbon sugars), both of which can be used as sources of energy.
Carbohydrates: Sugars

Sugars

In United States, the natural sugars of milk, fruits, vegetables, and grains account for about half of the sugar intake, the other half consists of concentrated sugars that have been refined and added to foods for a variety of purposes.

Sugars, important in nutrition, consist of monosaccharides, having the general formula C6H12O6, and disaccharides, having the general formula C12H22O11.

Although the monosaccharides consists of 3-carbon sugars (trioses), 4-carbon sugars (tetroses), 5-carbon sugars (pentoses), and 6-carbon sugars (hexoses), only the latter are important in human nutrition as sources of energy.

Three monosaccharides are important in nutrition: glucose, fructose and galactose. All three monosaccharides have the same number and kinds of atoms but in different arrangements.

Glucose, a 6-carbon sugar, is one of the simplest carbohydrates found in foods. While many foods contain traces of glucose, it is found in significant amounts only in fruits, such as grapes.

Most cells depend on glucose for their fuel to some extent and the cells of the brain and the rest of the nervous system depend almost exclusively on glucose for their energy.

Fructose, also a 6-carbon sugar, is found in ripened fruits and honey, both of these sugars can be utilizes by body as a source of energy. It is the sweetest of the natural sugars.

Other source of fructose include soft drinks, ready to eat cereals and other products sweetened with high fructose corn syrup.

Lactose, the 12-carbon sugar present in milk, is broken down in the intestine to glucose and lactose (6-carbon sugar), both of which can be used as sources of energy.

Maltose, another disaccharide, produced form starch in the malting of grains is much less effective sweetener than sucrose.

The used of added sugars had risen steadily over the past several decades, both in the United States and around the world, with soft drinks and sugared fruit drinks accounting for most of the increase.
Sugars