Glucose is a simple sugar with the molecular formula C6H12O6.
Glucose is the most abundant monosaccharide, a subcategory of carbohydrates.
Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight, where it is used to make cellulose in cell walls, the most abundant carbohydrate in the world.
In energy metabolism, glucose is the most important source of energy in all organisms.
Glucose for metabolism is stored as a polymer, in plants mainly as starch and amylopectin, and in animals as glycogen.
Glucose circulates in the blood of animals as blood sugar.
The naturally occurring form of glucose is d-glucose, while l-glucose is produced synthetically in comparatively small amounts and is of lesser importance.
Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose.
The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form.
Glucose is naturally occurring and is found in its free state in fruits and other parts of plants.
Glucose animals, glucose is released from the breakdown of glycogen in a process known as glycogenolysis.
Glucose, as intravenous sugar solution, is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.
Glucose is also on the list in combination with sodium chloride.
Glucose was first isolated from raisins in 1747 by the German chemist Andreas Marggraf.
Glucose was discovered in grapes by another German chemist – Johann Tobias Lowitz in 1792, and distinguished as being different from cane sugar (sucrose).
Glucose is the term coined by Jean Baptiste Dumas in 1838, which has prevailed in the chemical literature.
Friedrich August Kekulé proposed the term dextrose (from Latin dexter = right), because in aqueous solution of glucose, the plane of linearly polarized light is turned to the right.
In contrast, d-fructose (a ketohexose) and l-glucose turn linearly polarized light to the left.
The earlier notation according to the rotation of the plane of linearly polarized light (d and l-nomenclature) was later abandoned in favor of the d- and l-notation, which refers to the absolute configuration of the asymmetric center farthest from the carbonyl group, and in concordance with the configuration of d- or l-glyceraldehyde.
Since glucose is a basic necessity of many organisms, a correct understanding of its chemical makeup and structure contributed greatly to a general advancement in organic chemistry.
This understanding occurred largely as a result of the investigations of Emil Fischer, a German chemist who received the 1902 Nobel Prize in Chemistry for his findings.
The synthesis of glucose established the structure of organic material and consequently formed the first definitive validation of Jacobus Henricus van 't Hoff's theories of chemical kinetics and the arrangements of chemical bonds in carbon-bearing molecules.
Between 1891 and 1894, Fischer established the stereochemical configuration of all the known sugars and correctly predicted the possible isomers, applying Van 't Hoff's theory of asymmetrical carbon atoms.
The names initially referred to the natural substances. Their enantiomers were given the same name with the introduction of systematic nomenclatures, taking into account absolute stereochemistry (e.g. Fischer nomenclature, d/l nomenclature).
For the discovery of the metabolism of glucose Otto Meyerhof received the Nobel Prize in Physiology or Medicine in 1922.
Hans von Euler-Chelpin was awarded the Nobel Prize in Chemistry along with Arthur Harden in 1929 for their "research on the fermentation of sugar and their share of enzymes in this process".
In 1947, Bernardo Houssay (for his discovery of the role of the pituitary gland in the metabolism of glucose and the derived carbohydrates) as well as Carl and Gerty Cori (for their discovery of the conversion of glycogen from glucose) received the Nobel Prize in Physiology or Medicine.
In 1970, Luis Leloir was awarded the Nobel Prize in Chemistry for the discovery of glucose-derived sugar nucleotides in the biosynthesis of carbohydrates.
Glucose forms white or colorless solids that are highly soluble in water and acetic acid but poorly soluble in methanol and ethanol.
Glucose melt at 146 °C (295 °F) (α) and 150 °C (302 °F) (β), and decompose starting at 188 °C (370 °F) with release of various volatile products, ultimately leaving a residue of carbon.
Glucose has a dissociation exponent (pK) of 12.16 at 25˚C in methanol and water.
With six carbon atoms, it is classed as a hexose, a subcategory of the monosaccharides. d-Glucose is one of the sixteen aldohexose stereoisomers.
Glucose d-isomer, d-glucose, also known as dextrose, occurs widely in nature, but the l-isomer, l-glucose, does not.
Glucose can be obtained by hydrolysis of carbohydrates such as milk sugar (lactose), cane sugar (sucrose), maltose, cellulose, glycogen, etc. Dextrose is commonly commercially manufactured from cornstarch in the US and Japan, from potato and wheat starch in Europe, and from tapioca starch in tropical areas.
Glucose manufacturing process uses hydrolysis via pressurized steaming at controlled pH in a jet followed by further enzymatic depolymerization.
Unbonded glucose is one of the main ingredients of honey.
All forms of glucose are colorless and easily soluble in water, acetic acid, and several other solvents.
They are only sparingly soluble in methanol and ethanol.
Structure and nomenclature
Mutarotation of glucose.
Glucose is usually present in solid form as a monohydrate with a closed pyran ring (dextrose hydrate).
Glucose aqueous solution, on the other hand, it is an open-chain to a small extent and is present predominantly as α- or β-pyranose, which interconvert (see mutarotation).
From aqueous solutions, the three known forms can be crystallized: α-glucopyranose, β-glucopyranose and β-glucopyranose hydrate.
Glucose is a building block of the disaccharides lactose and sucrose (cane or beet sugar), of oligosaccharides such as raffinose and of polysaccharides such as starch and amylopectin, glycogen or cellulose.
The glass transition temperature of glucose is 31 °C and the Gordon–Taylor constant (an experimentally determined constant for the prediction of the glass transition temperature for different mass fractions of a mixture of two substances) is 4.5.
Glucose can exist in both a straight-chain and ring form.
Glucose open-chain form of glucose makes up less than 0.02% of the glucose molecules in an aqueous solution.
Glucose rest is one of two cyclic hemiacetal forms.
In its open-chain form, the glucose molecule has an open (as opposed to cyclic) unbranched backbone of six carbon atoms, where C-1 is part of an aldehyde group (C=O)−.
Therefore, glucose is also classified as an aldose, or an aldohexose.
The aldehyde group makes glucose a reducing sugar giving a positive reaction with the Fehling test.
From left to right: Haworth projections and ball-and-stick structures of the α- and β- anomers of D-glucopyranose (top row) and D-glucofuranose (bottom row)
In solutions, the open-chain form of glucose (either "D-" or "L-") exists in equilibrium with several cyclic isomers, each containing a ring of carbons closed by one oxygen atom.
In aqueous solution, however, more than 99% of glucose molecules exist as pyranose forms.
Glucose open-chain form is limited to about 0.25%, and furanose forms exist in negligible amounts.
The terms "glucose" and "D-glucose" are generally used for these cyclic forms as well.
The ring arises from the open-chain form by an intramolecular nucleophilic addition reaction between the aldehyde group (at C-1) and either the C-4 or C-5 hydroxyl group, forming a hemiacetal linkage, −C(OH)H−O−.
Glucose reaction between C-1 and C-5 yields a six-membered heterocyclic system called a pyranose, which is a monosaccharide sugar (hence "-ose") containing a derivatised pyran skeleton.
Glucose (much rarer) reaction between C-1 and C-4 yields a five-membered furanose ring, named after the cyclic ether furan.
In either case, each carbon in the ring has one hydrogen and one hydroxyl attached, except for the last carbon (C-4 or C-5) where the hydroxyl is replaced by the remainder of the open molecule (which is −(C(CH2OH)HOH)−H or −(CHOH)−H respectively).
Glucose ring-closing reaction can give two products, denoted "α-" and "β-" When a glucopyranose molecule is drawn in the Haworth projection, the designation "α-" means that the hydroxyl group attached to C-1 and the −CH2OH group at C-5 lies on opposite sides of the ring's plane (a trans arrangement), while "β-" means that they are on the same side of the plane (a cis arrangement).
Therefore, the open-chain isomer D-glucose gives rise to four distinct cyclic isomers: α-D-glucopyranose, β-D-glucopyranose, α-D-glucofuranose, and β-D-glucofuranose.
These five structures exist in equilibrium and interconvert, and the interconversion is much more rapid with acid catalysis.
Glucose other open-chain isomer L-glucose similarly gives rise to four distinct cyclic forms of L-glucose, each the mirror image of the corresponding D-glucose.
The glucopyranose ring (α or β) can assume several non-planar shapes, analogous to the "chair" and "boat" conformations of cyclohexane.
Similarly, the glucofuranose ring may assume several shapes, analogous to the "envelope" conformations of cyclopentane.
In the solid state, only the glucopyranose forms are observed.
Some derivatives of glucofuranose, such as 1,2-O-isopropylidene-d-glucofuranose are stable and can be obtained pure as crystalline solids.
For example, reaction of α-D-glucose with para-tolylboronic acid H3C−(C6H4)−B(OH)2 reforms the normal pyranose ring to yield the 4-fold ester α-D-glucofuranose-1,2∶3,5-bis(p-tolylboronate).
Mutarotation: d-glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other.
Glucoseepimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.
Mutarotation consists of a temporary reversal of the ring-forming reaction, resulting in the open-chain form, followed by a reforming of the ring.
Glucose ring closure step may use a different −OH group than the one recreated by the opening step (thus switching between pyranose and furanose forms), or the new hemiacetal group created on C-1 may have the same or opposite handedness as the original one (thus switching between the α and β forms).
Thus, though the open-chain form is barely detectable in solution, it is an essential component of the equilibrium.
The open-chain form is thermodynamically unstable, and it spontaneously isomerizes to the cyclic forms.
(Although the ring closure reaction could in theory create four- or three-atom rings, these would be highly strained, and are not observed in practice.) In solutions at room temperature, the four cyclic isomers interconvert over a time scale of hours, in a process called mutarotation.
Starting from any proportions, the mixture converges to a stable ratio of α:β 36:64.
Glucose ratio would be α:β 11:89 if it were not for the influence of the anomeric effect.
Mutarotation is considerably slower at temperatures close to 0 °C (32 °F).
Whether in water or the solid form, d-(+)-glucose is dextrorotatory, meaning it will rotate the direction of polarized light clockwise as seen looking toward the light source. The effect is due to the chirality of the molecules, and indeed the mirror-image isomer, l-(−)-glucose, is levorotatory (rotates polarized light counterclockwise) by the same amount.
Glucose strength of the effect is different for each of the five tautomers.
Note that the d- prefix does not refer directly to the optical properties of the compound.
Glucose indicates that the C-5 chiral centre has the same handedness as that of d-glyceraldehyde (which was so labelled because it is dextrorotatory).
The fact that d-glucose is dextrorotatory is a combined effect of its four chiral centres, not just of C-5; and indeed some of the other d-aldohexoses are levorotatory.
Glucose conversion between the two anomers can be observed in a polarimeter since pure α-dglucose has a specific rotation angle of +112.2°·ml/(dm·g), pure β- D- glucose of +17.5°·ml/(dm·g).
When equilibrium has been reached after a certain time due to mutarotation, the angle of rotation is +52.7°·ml/(dm·g).
By adding acid or base, this transformation is much accelerated.
Glucose equilibration takes place via the open-chain aldehyde form.
In dilute sodium hydroxide or other dilute bases, the monosaccharides mannose, glucose and fructose interconvert (via a Lobry de Bruyn–Alberda–Van Ekenstein transformation), so that a balance between these isomers is formed.
Glucose reaction proceeds via an enediol:
Metabolism of common monosaccharides and some biochemical reactions of glucose
Glucose is the most abundant monosaccharide.
Glucose is also the most widely used aldohexose in most living organisms.
One possible explanation for this is that glucose has a lower tendency than other aldohexoses to react nonspecifically with the amine groups of proteins.
Glucose reaction—glycation—impairs or destroys the function of many proteins, e.g. in glycated hemoglobin.
Glucose's low rate of glycation can be attributed to its having a more stable cyclic form compared to other aldohexoses, which means it spends less time than they do in its reactive open-chain form.
Glucose reason for glucose having the most stable cyclic form of all the aldohexoses is that its hydroxy groups (with the exception of the hydroxy group on the anomeric carbon of d-glucose) are in the equatorial position.
Presumably, glucose is the most abundant natural monosaccharide because it is less glycated with proteins than other monosaccharides.
Another hypothesis is that glucose, being the only d-aldohexose that has all five hydroxy substituents in the equatorial position in the form of β-d-glucose, is more readily accessible to chemical reactions,: 194, 199 for example, for esterification: 363 or acetal formation.
For this reason, d-glucose is also a highly preferred building block in natural polysaccharides (glycans). Polysaccharides that are composed solely of glucose are termed glucans.
Glucose is produced by plants through the photosynthesis using sunlight, water and carbon dioxide and can be used by all living organisms as an energy and carbon source.
However, most glucose does not occur in its free form, but in the form of its polymers, i.e. lactose, sucrose, starch and others which are energy reserve substances, and cellulose and chitin, which are components of the cell wall in plants or fungi and arthropods, respectively.
These polymers, when consumed by animals, fungi and bacteria, are degraded to glucose using enzymes.
All animals are also able to produce glucose themselves from certain precursors as the need arises.
Neurons, cells of the renal medulla and erythrocytes depend on glucose for their energy production.
In adult humans, there are about 18 g of glucose, of which about 4 g are present in the blood.
Approximately 180 to 220 g of glucose are produced in the liver of an adult in 24 hours.
Many of the long-term complications of diabetes (e.g., blindness, kidney failure, and peripheral neuropathy) are probably due to the glycation of proteins or lipids. In contrast, enzyme-regulated addition of sugars to protein is called glycosylation and is essential for the function of many proteins.
Ingested glucose initially binds to the receptor for sweet taste on the tongue in humans.
Glucose complex of the proteins T1R2 and T1R3 makes it possible to identify glucose-containing food sources.
Glucose mainly comes from food—about 300 g per day are produced by conversion of food,but it is also synthesized from other metabolites in the body's cells.
In humans, the breakdown of glucose-containing polysaccharides happens in part already during chewing by means of amylase, which is contained in saliva, as well as by maltase, lactase, and sucrase on the brush border of the small intestine.
Glucose is a building block of many carbohydrates and can be split off from them using certain enzymes.
Glucosidases, a subgroup of the glycosidases, first catalyze the hydrolysis of long-chain glucose-containing polysaccharides, removing terminal glucose.
In turn, disaccharides are mostly degraded by specific glycosidases to glucose.
Glucose names of the degrading enzymes are often derived from the particular poly- and disaccharide; inter alia, for the degradation of polysaccharide chains there are amylases (named after amylose, a component of starch), cellulases (named after cellulose), chitinases (named after chitin), and more.
Furthermore, for the cleavage of disaccharides, there are maltase, lactase, sucrase, trehalase, and others. In humans, about 70 genes are known that code for glycosidases.
They have functions in the digestion and degradation of glycogen, sphingolipids, mucopolysaccharides, and poly(ADP-ribose).
Humans do not produce cellulases, chitinases, or trehalases, but the bacteria in the gut flora do.
Glucoseorder to get into or out of cell membranes of cells and membranes of cell compartments, glucose requires special transport proteins from the major facilitator superfamily.
Glucose the small intestine (more precisely, in the jejunum),glucose is taken up into the intestinal epithelium with the help of glucose transporters via a secondary active transport mechanism called sodium ion-glucose symport via sodium/glucose cotransporter 1 (SGLT1).
Further transfer occurs on the basolateral side of the intestinal epithelial cells via the glucose transporter GLUT2,as well uptake into liver cells, kidney cells, cells of the islets of Langerhans, neurons, astrocytes, and tanycytes.
Glucose enters the liver via the portal vein and is stored there as a cellular glycogen.
Glucose the liver cell, it is phosphorylated by glucokinase at position 6 to form glucose 6-phosphate, which cannot leave the cell.
Glucose 6-phosphatase can convert glucose 6-phosphate back into glucose exclusively in the liver, so the body can maintain a sufficient blood glucose concentration.
Glucose other cells, uptake happens by passive transport through one of the 14 GLUT proteins.
Glucose the other cell types, phosphorylation occurs through a hexokinase, whereupon glucose can no longer diffuse out of the cell.
The glucose transporter GLUT1 is produced by most cell types and is of particular importance for nerve cells and pancreatic β-cells. GLUT3 is highly expressed in nerve cells.
Glucose from the bloodstream is taken up by GLUT4 from muscle cells (of the skeletal muscle and heart muscle) and fat cells.GLUT14 is expressed exclusively in testicles.
Excess glucose is broken down and converted into fatty acids, which are stored as triglycerides.
Glucose the kidneys, glucose in the urine is absorbed via SGLT1 and SGLT2 in the apical cell membranes and transmitted via GLUT2 in the basolateral cell membranes.
About 90% of kidney glucose reabsorption is via SGLT2 and about 3% via SGLT1.
Main articles: Gluconeogenesis and Glycogenolysis
In plants and some prokaryotes, glucose is a product of photosynthesis.
Glucose is also formed by the breakdown of polymeric forms of glucose like glycogen (in animals and mushrooms) or starch (in plants).
The cleavage of glycogen is termed glycogenolysis, the cleavage of starch is called starch degradation.
Glucose metabolic pathway that begins with molecules containing two to four carbon atoms (C) and ends in the glucose molecule containing six carbon atoms is called gluconeogenesis and occurs in all living organisms.
The smaller starting materials are the result of other metabolic pathways.
Ultimately almost all biomolecules come from the assimilation of carbon dioxide in plants during photosynthesis:
The free energy of formation of α-d-glucose is 917.2 kilojoules per mole: 59 In humans, gluconeogenesis occurs in the liver and kidney,but also in other cell types.
Glucose the liver about 150 g of glycogen are stored, in skeletal muscle about 250 g.
However, the glucose released in muscle cells upon cleavage of the glycogen can not be delivered to the circulation because glucose is phosphorylated by the hexokinase, and a glucose-6-phosphatase is not expressed to remove the phosphate group.
Unlike for glucose, there is no transport protein for glucose-6-phosphate.
Gluconeogenesis allows the organism to build up glucose from other metabolites, including lactate or certain amino acids, while consuming energy.
The renal tubular cells can also produce glucose.
Glucose also can be found outside of living organisms in the ambient environment.
Glucose concentrations in the atmosphere are detected via collection of samples by aircraft and are known to vary from location to location.
For example, glucose concentrations in atmospheric air from inland China range from 0.8-20.1 pg/l, whereas east coastal China glucose concentrations range from 10.3-142 pg/l.
Glucose metabolism and various forms of it in the process
Glucose-containing compounds and isomeric forms are digested and taken up by the body in the intestines, including starch, glycogen, disaccharides and monosaccharides.
Glucose is stored in mainly the liver and muscles as glycogen.
Glucose is distributed and used in tissues as free glucose.
Main articles: Glycolysis and Pentose phosphate pathway
In humans, glucose is metabolised by glycolysis and the pentose phosphate pathway.
Glycolysis is used by all living organisms,: 551 with small variations, and all organisms generate energy from the breakdown of monosaccharides.
Glucose the further course of the metabolism, it can be completely degraded via oxidative decarboxylation, the citric acid cycle (synonym Krebs cycle) and the respiratory chain to water and carbon dioxide.
Glucose there is not enough oxygen available for this, the glucose degradation in animals occurs anaerobic to lactate via lactic acid fermentation and releases less energy.
Muscular lactate enters the liver through the bloodstream in mammals, where gluconeogenesis occurs (Cori cycle).
With a high supply of glucose, the metabolite acetyl-CoA from the Krebs cycle can also be used for fatty acid synthesis.
Glucose is also used to replenish the body's glycogen stores, which are mainly found in liver and skeletal muscle. These processes are hormonally regulated.
Glucose other living organisms, other forms of fermentation can occur.
The bacterium Escherichia coli can grow on nutrient media containing glucose as the sole carbon source:
Glucose some bacteria and, in modified form, also in archaea, glucose is degraded via the Entner-Doudoroff pathway.
Use of glucose as an energy source in cells is by either aerobic respiration, anaerobic respiration, or fermentation.
Glucose first step of glycolysis is the phosphorylation of glucose by a hexokinase to form glucose 6-phosphate.
Glucose main reason for the immediate phosphorylation of glucose is to prevent its diffusion out of the cell as the charged phosphate group prevents glucose 6-phosphate from easily crossing the cell membrane.
Furthermore, addition of the high-energy phosphate group activates glucose for subsequent breakdown in later steps of glycolysis.
At physiological conditions, this initial reaction is irreversible.
In anaerobic respiration, one glucose molecule produces a net gain of two ATP molecules (four ATP molecules are produced during glycolysis through substrate-level phosphorylation, but two are required by enzymes used during the process).
In aerobic respiration, a molecule of glucose is much more profitable in that a maximum net production of 30 or 32 ATP molecules (depending on the organism) through oxidative phosphorylation is generated.
Click on genes, proteins and metabolites below to link to respective articles.
Tumor cells often grow comparatively quickly and consume an above-average amount of glucose by glycolysis,which leads to the formation of lactate, the end product of fermentation in mammals, even in the presence of oxygen.
Glucose effect is called the Warburg effect. For the increased uptake of glucose in tumors various SGLT and GLUT are overly produced.
In yeast, ethanol is fermented at high glucose concentrations, even in the presence of oxygen (which normally leads to respiration but not to fermentation).
Glucose effect is called the Crabtree effect.
Glucose can also degrade to form carbon dioxide through abiotic means.
This has been demonstrated to occur experimentally via oxidation and hydrolysis at 22˚C and a pH of 2.5.
Diagram showing the possible intermediates in glucose degradation; Metabolic pathways orange: glycolysis, green: Entner-Doudoroff pathway, phosphorylating, yellow: Entner-Doudoroff pathway, non-phosphorylating
Glucose is a ubiquitous fuel in biology.
Glucose is used as an energy source in organisms, from bacteria to humans, through either aerobic respiration, anaerobic respiration (in bacteria), or fermentation.
Glucose is the human body's key source of energy, through aerobic respiration, providing about 3.75 kilocalories (16 kilojoules) of food energy per gram.
Breakdown of carbohydrates (e.g., starch) yields mono- and disaccharides, most of which is glucose.
Through glycolysis and later in the reactions of the citric acid cycle and oxidative phosphorylation, glucose is oxidized to eventually form carbon dioxide and water, yielding energy mostly in the form of ATP.
Glucose insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood.
Glucose physiological caloric value of glucose, depending on the source, is 16.2 kilojoules per gram and 15.7 kJ/g (3.74 kcal/g), respectively.
Glucose high availability of carbohydrates from plant biomass has led to a variety of methods during evolution, especially in microorganisms, to utilize the energy and carbon storage glucose.
Differences exist in which end product can no longer be used for energy production.
The presence of individual genes, and their gene products, the enzymes, determine which reactions are possible.
The metabolic pathway of glycolysis is used by almost all living beings.
An essential difference in the use of glycolysis is the recovery of NADPH as a reductant for anabolism that would otherwise have to be generated indirectly.
Glucose and oxygen supply almost all the energy for the brain, so its availability influences psychological processes.
When glucose is low, psychological processes requiring mental effort (e.g., self-control, effortful decision-making) are impaired.
In the brain, which is dependent on glucose and oxygen as the major source of energy, the glucose concentration is usually 4 to 6 mM (5 mM equals 90 mg/dL), but decreases to 2 to 3 mM when fasting.
Confusion occurs below 1 mM and coma at lower levels.
The glucose in the blood is called blood sugar.
Blood sugar levels are regulated by glucose-binding nerve cells in the hypothalamus.
In addition, glucose in the brain binds to glucose receptors of the reward system in the nucleus accumbens.
The binding of glucose to the sweet receptor on the tongue induces a release of various hormones of energy metabolism, either through glucose or through other sugars, leading to an increased cellular uptake and lower blood sugar levels.
Artificial sweeteners do not lower blood sugar levels.
The blood sugar content of a healthy person in the short-time fasting state, e.g. after overnight fasting, is about 70 to 100 mg/dL of blood (4 to 5.5 mM).
In blood plasma, the measured values are about 10–15% higher.
In addition, the values in the arterial blood are higher than the concentrations in the venous blood since glucose is absorbed into the tissue during the passage of Glucose capillary bed.
Also in the capillary blood, which is often used for blood sugar determination, the values are sometimes higher than in the venous blood. The glucose content of the blood is regulated by the hormones insulin, incretin and glucagon.
Insulin lowers the glucose level, glucagon increases it.
Furthermore, the hormones adrenaline, thyroxine, glucocorticoids, somatotropin and adrenocorticotropin lead to an increase in the glucose level.
Glucose is also a hormone-independent regulation, which is referred to as glucose autoregulation.
After food intake the blood sugar concentration increases. Values over 180 mg/dL in venous whole blood are pathological and are termed hyperglycemia, values below 40 mg/dL are termed hypoglycaemia.
When needed, glucose is released into the bloodstream by glucose-6-phosphatase from glucose-6-phosphate originating from liver and kidney glycogen, thereby regulating the homeostasis of blood glucose concentration.
In ruminants, the blood glucose concentration is lower (60 mg/dL in cattle and 40 mg/dL in sheep), because the carbohydrates are converted more by their gut flora into short-chain fatty acids.
Some glucose is converted to lactic acid by astrocytes, which is then utilized as an energy source by brain cells; some glucose is used by intestinal cells and red blood cells, while the rest reaches the liver, adipose tissue and muscle cells, where it is absorbed and stored as glycogen (under the influence of insulin).
Liver cell glycogen can be converted to glucose and returned to the blood when insulin is low or absent; muscle cell glycogen is not returned to the blood because of a lack of enzymes.
Glucose fat cells, glucose is used to power reactions that synthesize some fat types and have other purposes.
Glycogen is the body's "glucose energy storage" mechanism, because it is much more "space efficient" and less reactive than glucose itself.
As a result of its importance in human health, glucose is an analyte in glucose tests that are common medical blood tests.
Eating or fasting prior to taking a blood sample has an effect on analyses for glucose in the blood; a high fasting glucose blood sugar level may be a sign of prediabetes or diabetes mellitus.
The glycemic index is an indicator of the speed of resorption and conversion to blood glucose levels from ingested carbohydrates, measured as the area under the curve of blood glucose levels after consumption in comparison to glucose (glucose is defined as 100).
Glucose clinical importance of the glycemic index is controversial, as foods with high fat contents slow the resorption of carbohydrates and lower the glycemic index, e.g. ice cream.
An alternative indicator is the insulin index, measured as the impact of carbohydrate consumption on the blood insulin levels.
The glycemic load is an indicator for the amount of glucose added to blood glucose levels after consumption, based on the glycemic index and the amount of consumed food.
Organisms use glucose as a precursor for the synthesis of several important substances.
Starch, cellulose, and glycogen ("animal starch") are common glucose polymers (polysaccharides).
Some of these polymers (starch or glycogen) serve as energy stores, while others (cellulose and chitin, which is made from a derivative of glucose) have structural roles.
Oligosaccharides of glucose combined with other sugars serve as important energy stores.
These include lactose, the predominant sugar in milk, which is a glucose-galactose disaccharide, and sucrose, another disaccharide which is composed of glucose and fructose.
Glucose is also added onto certain proteins and lipids in a process called glycosylation.
Glucose is often critical for their functioning.
The enzymes that join glucose to other molecules usually use phosphorylated glucose to power the formation of the new bond by coupling it with the breaking of the glucose-phosphate bond.
Other than its direct use as a monomer, glucose can be broken down to synthesize a wide variety of other biomolecules.
This is important, as glucose serves both as a primary store of energy and as a source of organic carbon.
Glucose can be broken down and converted into lipids.
Glucose is also a precursor for the synthesis of other important molecules such as vitamin C (ascorbic acid).
Glucose living organisms, glucose is converted to several other chemical compounds that are the starting material for various metabolic pathways.
Among them, all other monosaccharides such as fructose (via the polyol pathway),mannose (the epimer of glucose at position 2), galactose (the epimer at position 4), fucose, various uronic acids and the amino sugars are produced from glucose.
In addition to the phosphorylation to glucose-6-phosphate, which is part of the glycolysis, glucose can be oxidized during its degradation to glucono-1,5-lactone. Glucose is used in some bacteria as a building block in the trehalose or the dextran biosynthesis and in animals as a building block of glycogen.
Glucose can also be converted from bacterial xylose isomerase to fructose.
In addition, glucose metabolites produce all nonessential amino acids, sugar alcohols such as mannitol and sorbitol, fatty acids, cholesterol and nucleic acids.
Finally, glucose is used as a building block in the glycosylation of proteins to glycoproteins, glycolipids, peptidoglycans, glycosides and other substances (catalyzed by glycosyltransferases) and can be cleaved from them by glycosidases.
Diabetes is a metabolic disorder where the body is unable to regulate levels of glucose in the blood either because of a lack of insulin in the body or the failure, by cells in the body, to respond properly to insulin.
Each of these situations can be caused by persistently high elevations of blood glucose levels, through pancreatic burnout and insulin resistance.
Glucose pancreas is the organ responsible for the secretion of the hormones insulin and glucagon.
Insulin is a hormone that regulates glucose levels, allowing the body's cells to absorb and use glucose.
Without it, glucose cannot enter the cell and therefore cannot be used as fuel for the body's functions.
Glucose the pancreas is exposed to persistently high elevations of blood glucose levels, the insulin-producing cells in the pancreas could be damaged, causing a lack of insulin in the body.
Insulin resistance occurs when the pancreas tries to produce more and more insulin in response to persistently elevated blood glucose levels.
Eventually, the rest of the body becomes resistant to the insulin that the pancreas is producing, thereby requiring more insulin to achieve the same blood glucose-lowering effect, and forcing the pancreas to produce even more insulin to compete with the resistance.
This negative spiral contributes to pancreatic burnout, and the disease progression of diabetes.
To monitor the body's response to blood glucose-lowering therapy, glucose levels can be measured.
Blood glucose monitoring can be performed by multiple methods, such as the fasting glucose test which measures the level of glucose in the blood after 8 hours of fasting.
Another test is the 2-hour glucose tolerance test (GTT) – for this test, the person has a fasting glucose test done, then drinks a 75-gram glucose drink and is retested.
This test measures the ability of the person's body to process glucose.
Over time the blood glucose levels should decrease as insulin allows it to be taken up by cells and exit the blood stream.
Glucose, 5% solution for infusions
Individuals with diabetes or other conditions that result in low blood sugar often carry small amounts of sugar in various forms.
One sugar commonly used is glucose, often in the form of glucose tablets (glucose pressed into a tablet shape sometimes with one or more other ingredients as a binder), hard candy, or sugar packet.
Most dietary carbohydrates contain glucose, either as their only building block (as in the polysaccharides starch and glycogen), or together with another monosaccharide (as in the hetero-polysaccharides sucrose and lactose).
Unbounded glucose is one of the main ingredients of honey.
Glucose is extremely abundant and has been isolated from a variety of natural sources across the world, including male cones of the coniferous tree Wollemia nobilis in Rome, the roots of Ilex asprella plants in China, and straws from rice in California.
Glucose is produced industrially from starch by enzymatic hydrolysis using glucose amylase or by the use of acids.
Glucose enzymatic hydrolysis has largely displaced the acid-catalyzed hydrolysis.
Glucose result is glucose syrup (enzymatically with more than 90% glucose in the dry matter) with an annual worldwide production volume of 20 million tonnes (as of 2011).
This is the reason for the former common name "starch sugar".
The amylases most often come from Bacillus licheniformis or Bacillus subtilis (strain MN-385), which are more thermostable than the originally used enzymes.
Starting in 1982, pullulanases from Aspergillus niger were used in the production of glucose syrup to convert amylopectin to starch (amylose), thereby increasing the yield of glucose.
Glucose reaction is carried out at a pH = 4.6–5.2 and a temperature of 55–60 °C.
Corn syrup has between 20% and 95% glucose in the dry matter.
The Japanese form of the glucose syrup, Mizuame, is made from sweet potato or rice starch.
Maltodextrin contains about 20% glucose.
Many crops can be used as the source of starch.
Maize,rice,wheat,cassava,potato, barley, sweet potato,corn husk and sago are all used in various parts of the world.
In the United States, corn starch (from maize) is used almost exclusively.
Some commercial glucose occurs as a component of invert sugar, a roughly 1:1 mixture of glucose and fructose that is produced from sucrose.
In principle, cellulose could be hydrolysed to glucose, but this process is not yet commercially practical.
Conversion to fructose
Main article: isoglucose
In the USA almost exclusively corn (more precisely: corn syrup) is used as glucose source for the production of isoglucose, which is a mixture of glucose and fructose, since fructose has a higher sweetening power — with same physiological calorific value of 374 kilocalories per 100 g.
The annual world production of isoglucose is 8 million tonnes (as of 2011).
When made from corn syrup, the final product is high fructose corn syrup (HFCS).
Relative sweetness of various sugars in comparison with sucrose
Glucose is mainly used for the production of fructose and in the production of glucose-containing foods.
Glucose foods, it is used as a sweetener, humectant, to increase the volume and to create a softer mouthfeel.
Various sources of glucose, such as grape juice (for wine) or malt (for beer), are used for fermentation to ethanol during the production of alcoholic beverages.
Most soft drinks in the US use HFCS-55 (with a fructose content of 55% in the dry mass), while most other HFCS-sweetened foods in the US use HFCS-42 (with a fructose content of 42% in the dry mass).
Glucose the neighboring country Mexico, on the other hand, cane sugar is used in the soft drink as a sweetener, which has a higher sweetening power.
In addition, glucose syrup is used, inter alia, in the production of confectionery such as candies, toffee and fondant.
Typical chemical reactions of glucose when heated under water-free conditions are the caramelization and, in presence of amino acids, the maillard reaction.
In addition, various organic acids can be biotechnologically produced from glucose, for example by fermentation with Clostridium thermoaceticum to produce acetic acid, with Penicillium notatum for the production of araboascorbic acid, with Rhizopus delemar for the production of fumaric acid, with Aspergillus niger for the production of gluconic acid, with Candida brumptii to produce isocitric acid, with Aspergillus terreus for the production of itaconic acid, with Pseudomonas fluorescens for the production of 2-ketogluconic acid, with Gluconobacter suboxydans for the production of 5-ketogluconic acid, with Aspergillus oryzae for the production of kojic acid, with Lactobacillus delbrueckii for the production of lactic acid, with Lactobacillus brevis for the production of malic acid, with Propionibacter shermanii for the production of propionic acid, with Pseudomonas aeruginosa for the production of pyruvic acid and with Gluconobacter suboxydans for the production of tartaric acid Potent, bioactive natural products like triptolide that inhibit mammalian transcription via inhibition of the XPB subunit of the general transcription factor TFIIH has been recently reported as a glucose conjugate for targeting hypoxic cancer cells with increased glucose transporter expression.
Recently, glucose has been gaining commercial use as a key component of "kits" containing lactic acid and insulin intended to induce hypoglycemia and hyperlactatemia to combat different cancers and infections.
Specifically, when a glucose molecule is to be detected at a certain position in a larger molecule, nuclear magnetic resonance spectroscopy, X-ray crystallography analysis or lectin immunostaining is performed with concanavalin A reporter enzyme conjugate (that binds only glucose or mannose).
Classical qualitative detection reactions
These reactions have only historical significance:
Glucose Fehling test is a classic method for the detection of aldoses.
Due to mutarotation, glucose is always present to a small extent as an open-chain aldehyde.
By adding the Fehling reagents (Fehling (I) solution and Fehling (II) solution), the aldehyde group is oxidized to a carboxylic acid, while the Cu2+ tartrate complex is reduced to Cu+ and forms a brick red precipitate (Cu2O).
Glucose the Tollens test, after addition of ammoniacal AgNO3 to the sample solution, Ag+ is reduced by glucose to elemental silver.
Glucose Barfoed's test, a solution of dissolved copper acetate, sodium acetate and acetic acid is added to the solution of the sugar to be tested and subsequently heated in a water bath for a few minutes.
Glucose and other monosaccharides rapidly produce a reddish color and reddish brown copper(I) oxide (Cu2O).
As a reducing sugar, glucose reacts in the Nylander's test.
Upon heating a dilute potassium hydroxide solution with glucose to 100 °C, a strong reddish browning and a caramel-like odor develops.
Concentrated sulfuric acid dissolves dry glucose without blackening at room temperature forming sugar sulfuric acid.
Glucose a yeast solution, alcoholic fermentation produces carbon dioxide in the ratio of 2.0454 molecules of glucose to one molecule of CO2.
Glucose forms a black mass with stannous chloride.
Glucose an ammoniacal silver solution, glucose (as well as lactose and dextrin) leads to the deposition of silver.
Glucose an ammoniacal lead acetate solution, white lead glycoside is formed in the presence of glucose, which becomes less soluble on cooking and turns brown.
Glucose an ammoniacal copper solution, yellow copper oxide hydrate is formed with glucose at room temperature, while red copper oxide is formed during boiling (same with dextrin, except for with an ammoniacal copper acetate solution).
With Hager's reagent, glucose forms mercury oxide during boiling.
An alkaline bismuth solution is used to precipitate elemental, black-brown bismuth with glucose.
Glucose boiled in an ammonium molybdate solution turns the solution blue.
A solution with indigo carmine and sodium carbonate destains when boiled with glucose.
Refractometry and polarimetry
In concentrated solutions of glucose with a low proportion of other carbohydrates, its concentration can be determined with a polarimeter.
For sugar mixtures, the concentration can be determined with a refractometer, for example in the Oechsle determination in the course of the production of wine.
Photometric enzymatic methods in solution
Main article: Glucose oxidation reaction
The enzyme glucose oxidase (GOx) converts glucose into gluconic acid and hydrogen peroxide while consuming oxygen.
Another enzyme, peroxidase, catalyzes a chromogenic reaction (Trinder reaction) of phenol with 4-aminoantipyrine to a purple dye.
Photometric test-strip method
Glucose test-strip method employs the above-mentioned enzymatic conversion of glucose to gluconic acid to form hydrogen peroxide.
Glucose reagents are immobilised on a polymer matrix, the so-called test strip, which assumes a more or less intense color.
This can be measured reflectometrically at 510 nm with the aid of an LED-based handheld photometer.
Glucose allows routine blood sugar determination by laymen.
In addition to the reaction of phenol with 4-aminoantipyrine, new chromogenic reactions have been developed that allow photometry at higher wavelengths (550 nm, 750 nm).
Amperometric glucose sensor
Glucose electroanalysis of glucose is also based on the enzymatic reaction mentioned above.
Glucose produced hydrogen peroxide can be amperometrically quantified by anodic oxidation at a potential of 600 mV.
Glucose GOx is immobilised on the electrode surface or in a membrane placed close to the electrode.
Precious metals such as platinum or gold are used in electrodes, as well as carbon nanotube electrodes, which e.g. are doped with boron.
Cu–CuO nanowires are also used as enzyme-free amperometric electrodes.
This way a detection limit of 50 µmol/L has been achieved.
A particularly promising method is the so-called "enzyme wiring".
In this case, the electron flowing during the oxidation is transferred directly from the enzyme via a molecular wire to the electrode.
Other sensory methods
There are a variety of other chemical sensors for measuring glucose.
Given the importance of glucose analysis in the life sciences, numerous optical probes have also been developed for saccharides based on the use of boronic acids, which are particularly useful for intracellular sensory applications where other (optical) methods are not or only conditionally usable.
In addition to the organic boronic acid derivatives, which often bind highly specifically to the 1,2-diol groups of sugars, there are also other probe concepts classified by functional mechanisms which use selective glucose-binding proteins (e.g. concanavalin A) as a receptor.
Furthermore, methods were developed which indirectly detect the glucose concentration via the concentration of metabolised products, e.g. by the consumption of oxygen using fluorescence-optical sensors.
Finally, there are enzyme-based concepts that use the intrinsic absorbance or fluorescence of (fluorescence-labeled) enzymes as reporters.
Glucose can be quantified by copper iodometry.
Glucose particular, for the analysis of complex mixtures containing glucose, e.g. in honey, chromatographic methods such as high performance liquid chromatography and gas chromatography are often used in combination with mass spectrometry.
Taking into account the isotope ratios, it is also possible to reliably detect honey adulteration by added sugars with these methods.
Derivatisation using silylation reagents is commonly used.
Also, the proportions of di- and trisaccharides can be quantified.
Glucose vivo analysis
Glucose uptake in cells of organisms is measured with 2-deoxy-D-glucose or fluorodeoxyglucose.
(18F)fluorodeoxyglucose is used as a tracer in positron emission tomography in oncology and neurology,where it is by far the most commonly used diagnostic agent.
Pronunciation /ˈɡluːkoʊz/, /ɡluːkoʊs/
Allowed trivial names:
Preferred IUPAC name:
PINs are not identified for natural products.
Beilstein Reference: 1281604
Gmelin Reference: 83256
Chemical formula: C6H12O6
Molar mass: 180.156 g/mol
Appearance: White powder
Density :1.54 g/cm3
Melting point: α-d-Glucose: 146 °C (295 °F; 419 K)
β-d-Glucose: 150 °C (302 °F; 423 K)
Solubility in water: 909 g/L (25 °C (77 °F))
Magnetic susceptibility (χ): −101.5×10−6 cm3/mol
Dipole moment: 8.6827
Heat capacity (C): 218.6 J/(K·mol)
Std molar entropy :(So298) 209.2 J/(K·mol)
Std enthalpy of formation (ΔfH⦵298): −1271 kJ/mol
Heat of combustion, higher value (HHV): 2,805 kJ/mol (670 kcal/mol)
ATC code: B05CX01 (WHO) V04CA02 (WHO), V06DC01 (WHO)
glucose, also called dextrose, one of a group of carbohydrates known as simple sugars (monosaccharides).
Glucose (from Greek glykys; “sweet”) has the molecular formula C6H12O6.
Glucose is found in fruits and honey and is the major free sugar circulating in the blood of higher animals.
Glucose is the source of energy in cell function, and the regulation of its metabolism is of great importance (see fermentation; gluconeogenesis).
Molecules of starch, the major energy-reserve carbohydrate of plants, consist of thousands of linear glucose units.
Another major compound composed of glucose is cellulose, which is also linear.
Dextrose is the molecule D-glucose.
A related molecule in animals is glycogen, the reserve carbohydrate in most vertebrate and invertebrate animal cells, as well as those of numerous fungi and protozoans.
See also polysaccharide.
What is glucose?
You may know glucose by another name: blood sugar.
Glucose is key to keeping the mechanisms of the body in top working order.
When our glucose levels are optimal, it often goes unnoticed.
But when they stray from recommended boundaries, you’ll notice the unhealthy effect it has on normal functioning.
So what is glucose, exactly?
Glucose the simplest of the carbohydrates, making it a monosaccharide.
Glucose means it has one sugar.
Glucose not alone.
Other monosaccharides include fructose, galactose, and ribose.
Along with fat, glucose is one of the body’s preferred sources of fuel in the form of carbohydrates.
People get glucose from bread, fruits, vegetables, and dairy products.
You need food to create the energy that helps keep you alive.
While glucose is important, like with so many things, it’s best in moderation.
Glucose levels that are unhealthy or out of control can have permanent and serious effects.
How does the body process glucose?
Our body processes glucose multiple times a day, ideally.
When we eat, our body immediately starts working to process glucose.
Enzymes start the breakdown process with help from the pancreas.
Glucose pancreas, which produces hormones including insulin, is an integral part of how our body deals with glucose.
When we eat, our body tips the pancreas off that it needs to release insulin to deal with the rising blood sugar level.
Some people, however, can’t rely on their pancreas to jump in and do the work it’s supposed to do.
One way diabetes occurs is when the pancreas doesn’t produce insulin in the way it should.
Glucose this case, people need outside help (insulin injections) to process and regulate glucose in the body.
Another cause of diabetes is insulin resistance, where the liver doesn’t recognize insulin that’s in the body and continues to make inappropriate amounts of glucose.
The liver is an important organ for sugar control, as it helps with glucose storage and makes glucose when necessary.
Glucose the body doesn’t produce enough insulin, it can result in the release of free fatty acids from fat stores.
This can lead to a condition called ketoacidosis.
Ketones, waste products created when the liver breaks down fat, can be toxic in large quantities.
How do you test your glucose?
Testing glucose levels is especially important for people with diabetes.
Most people with the condition are used to dealing with blood sugar checks as part of their daily routine.
One of the most common ways to test glucose at home involves a very simple blood test.
A finger prick, usually using a small needle called a lancet, produces a drop that is put onto a test strip.
The strip is put into a meter, which measures blood sugar levels.
Glucose can usually give you a reading in under 20 seconds.
What Is Glucose?
By Stephanie Watson
Medically Reviewed by Carol DerSarkissian, MD on June 13, 2020
IN THIS ARTICLE
How Your Body Makes Glucose
Energy and Storage
Blood Glucose Levels and Diabetes
Glucose comes from the Greek word for "sweet."
It's a type of sugar you get from foods you eat, and your body uses it for energy.
As it travels through your bloodstream to your cells, it's called blood glucose or blood sugar.
Insulin is a hormone that moves glucose from your blood into the cells for energy and storage.
People with diabetes have higher-than-normal levels of glucose in their blood.
Either they don't have enough insulin to move it through or their cells don't respond to insulin as well as they should.
High blood glucose for a long period of time can damage your kidneys, eyes, and other organs.
How Your Body Makes Glucose
Glucose mainly comes from foods rich in carbohydrates, like bread, potatoes, and fruit.
As you eat, food travels down your esophagus to your stomach. There, acids and enzymes break it down into tiny pieces.
During that process, glucose is released.
Glucose goes into your intestines where it's absorbed. From there, it passes into your bloodstream.
Once in the blood, insulin helps glucose get to your cells.
Energy and Storage
Your body is designed to keep the level of glucose in your blood constant.
Beta cells in your pancreas monitor your blood sugar level every few seconds.
When your blood glucose rises after you eat, the beta cells release insulin into your bloodstream.
Insulin acts like a key, unlocking muscle, fat, and liver cells so glucose can get inside them.
Most of the cells in your body use glucose along with amino acids (the building blocks of protein) and fats for energy.
But it's the main source of fuel for your brain.
Nerve cells and chemical messengers there need it to help them process information.
Without it, your brain wouldn't be able to work well.
After your body has used the energy it needs, the leftover glucose is stored in little bundles called glycogen in the liver and muscles.
Your body can store enough to fuel you for about a day.
After you haven't eaten for a few hours, your blood glucose level drops.
Your pancreas stops churning out insulin. Alpha cells in the pancreas begin to produce a different hormone called glucagon.
Glucose signals the liver to break down stored glycogen and turn it back into glucose.
That travels to your bloodstream to replenish your supply until you're able to eat again.
Your liver can also make its own glucose using a combination of waste products, amino acids, and fats.
Blood Glucose Levels and Diabetes
Your blood sugar level normally rises after you eat.
Then it dips a few hours later as insulin moves glucose into your cells.
Between meals, your blood sugar should be less than 100 milligrams per deciliter (mg/dl).
Glucose is called your fasting blood sugar level.
There are two types of diabetes:
Glucose type 1 diabetes, your body doesn't have enough insulin.
Glucose immune system attacks and destroys cells of the pancreas, where insulin is made.
Glucose type 2 diabetes, the cells don't respond to insulin like they should.
So the pancreas needs to make more and more insulin to move glucose into the cells.
Eventually, the pancreas is damaged and can't make enough insulin to meet the body's needs.
Without enough insulin, glucose can't move into the cells. The blood glucose level stays high.
A level over 200 mg/dl 2 hours after a meal or over 125 mg/dl fasting is high blood glucose, called hyperglycemia.
Too much glucose in your bloodstream for a long period of time can damage the vessels that carry oxygen-rich blood to your organs.
High blood sugar can increase your risk for:
Heart disease, heart attack, and stroke
Eye disease called retinopathy
People with diabetes need to test their blood sugar often. Exercise, diet, and medicine can help keep blood glucose in a healthy range and prevent these complications.
Catalogue Number: 346351
Brand Family: Calbiochem®
Synonyms :Dextrose, α-D-Glucose
CAS number: 50-99-7
Form :White powder
Hill Formula: C₆H₁₂O₆
Chemical formula: C₆H₁₂O₆
Quality Level: MQ100
Contaminants :Maltose: ≤0.2%; heavy metals: ≤0.001%
Safety :Information according to GHS
Storage and Shipping Information
Ship Code: Ambient Temperature Only
Toxicity: Standard Handling
Storage +15°C to +30°C
Do not freeze :Ok to freeze
Special Instructions: Following reconstitution, filter-sterilize and store at room temperature.
Stock solutions are stable for several months at room temperature.
Glucose is the main type of sugar in the blood and is the major source of energy for the body's cells.
Glucose comes from the foods we eat or the body can make it from other substances.
Glucose is carried to the cells through the bloodstream.
Several hormones, including insulin, control glucose levels in the blood.
What is a blood glucose test?
A blood glucose test is a blood test that screens for diabetes by measuring the level of glucose (sugar) in a person’s blood.
Who is most at risk for developing diabetes?
The following categories of people are considered "high-risk" candidates for developing diabetes:
Individuals who are overweight or obese
Individuals who are 45 years of age or older
Individuals with first-degree relatives with diabetes (such as parents, children, or siblings)
Individuals who are African-American, Alaska Native, American Indian, Asia American, Hispanic/Latino, Native Hawaiian, Pacific Islanders,
Women who developed diabetes while they were pregnant or gave birth to large babies (9 pounds or more)
Individuals with high blood pressure (140/90 or higher)
Individuals with high-density lipoprotein (HDL, the "good cholesterol level") below 25 mg/dl or triglyceride levels at or above 250 mg/dl
Individuals who have impaired fasting glucose or impaired glucose tolerance
Individuals who are physically inactive; engaging in exercise less than three times a week
Individuals who have polycystic ovary syndrome, also called PCOS
Individuals who have acanthosis nigricans -- dark, thick and velvety skin around your neck or armpits
In addition to testing the above individuals at high risk, the American Diabetes Association also recommends screening all individuals age 45 and older.
How can one tell if I have diabetes by examining my blood?
Your body converts sugar, also called glucose, into energy so your body can function.
Glucose sugar comes from the foods you eat and is released from storage from your body’s own tissues.
Insulin is a hormone made by the pancreas.
Glucose job is to move glucose from the bloodstream into the cells of tissues.
After you eat, the level of glucose in the blood rises sharply.
The pancreas responds by releasing enough insulin to handle the increased level of glucose — moving the glucose out of the blood and into cells.
This helps return the blood glucose level to its former, lower level.
If a person has diabetes, two situations may cause the blood sugar to increase:
The pancreas does not make enough insulin
The insulin does not work properly
As a result of either of these situations, the blood sugar level remains high, a condition called hyperglycemia or diabetes mellitus.
Glucose left undiagnosed and untreated, the eyes, kidneys, nerves, heart, blood vessels and other organs can be damaged.
Measuring your blood glucose levels allows you and your doctor to know if you have, or are at risk for, developing diabetes.
Much less commonly, the opposite can happen too.
Too low a level of blood sugar, a condition called hypoglycemia, can be caused by the presence of too much insulin or by other hormone disorders or liver disease.
How do I prepare for the plasma glucose level test and how are the results interpreted?
To get an accurate plasma glucose level, you must have fasted (not eaten or had anything to drink except water) for at least 8 hours prior to the test.
When you report to the clinic or laboratory, a small sample of blood will be taken from a vein in your arm.
According to the practice recommendations of the American Diabetes Association, the results of the blood test are interpreted as follows:
Fasting blood glucose level
If your blood glucose level is 70 to 99* mg/dL (3.9 to 5.5 mmol/L). . .
What it means: Your glucose level is within the normal range
If your blood glucose level is 100 to 125 mg/dL (5.6 to 6.9 mmol/L). . .
What it means: You have an impaired fasting glucose level (pre-diabetes**) . . .
If your blood glucose level is 126 mg/dl (7.0 mmol/L ) or higher on more than one testing occasion
What it means: You have diabetes
Glucose is a monosaccharide and is the primary metabolite for energy production in the body.
Complex carbohydrates are ultimately broken down in the digestive system into glucose and other monosaccharides, such as fructose or galactose, prior to absorption in the small intestine; of note, insulin is not required for the uptake of glucose by the intestinal cells.
Glucose is transported into the cells by an active, energy-requiring process that involves a specific transport protein and requires a concurrent uptake of sodium ions.
In the blood circulation, the concentration of glucose is tightly regulated by hormones such as insulin, cortisol, and glucagon, which regulate glucose entry into cells and affect various metabolic processes such as glycolysis, gluconeogenesis, and glycogenolysis.
Glucose belongs to the family of carbohydrates.
Glucose is a monosaccharide (simple sugar) naturally present in all living beings on Earth and is their most important source of energy.
Glucose is found in high quantities in fruit (including berries), vegetables and honey.
When combined with other monosaccharides, such as fructose, it forms sucrose (table sugar) and lactose.
Two glucose molecules form maltose, a disaccharide resulting from the hydrolysis of cereal starch.
Maltose has slightly less sweetening power than sucrose.
Athletes use it for a quick supply of energy, whereas in bakeries it is useful for the fermentation of leavened dough. Maltose is also found in the germinated cereal grains used to make many types of beer.
Starch consists of a large number of glucose molecules linked to each other in long chains.
Cellulose is a polysaccharide made up of complex chains of starch. Unlike herbivorous mammals, the human body is unable to digest cellulose, so it serves as roughage in our diet.
Glc concentrations in tissues and body fluids are stabilized by many diverse mechanisms, many of which involve the action of specific hormones.
Overall homeostasis is maintained through directing the flux of Glc to or from glycogen stores, balancing glycolysis versus gluconeogenesis, and promoting protein catabolism in times of need.
Hormonal regulation: Among the many hormones with some effect on particular tissues or metabolic sequences a few stand out because of their dominant and overriding actions on Glc disposition.
Insulin promotes uptake and oxidation of Glc by tissues and favors storage, particularly in the postprandial phase.
Glucagon in response to low blood Glc concentration increases Glc release from storage and synthesis from precursors.
Adrenaline (epinephrine) mobilizes stores and accelerates utilization.
Insulin is produced in the beta cells of pancreatic islet cells and released in a zinc-dependent process together with its companion amylin.
The rate of production and release into circulation is related to Glc-sensing mechanisms in the beta cell.
ATP generation from Glc and cytosolic calcium concentration are thought to be critical for Glc sensing.
A zinc-containing enzyme, insulysin (EC188.8.131.52), inactivates insulin irreversibly in many tissues (Ding et al., 1992). Insulysin activity is inhibited by high concentrations of both amylin and insulin (Mukherjee et al., 2000).
Insulin binds to specific insulin receptors in muscles, adipocytes, and some other insulin-sensitive tissues and triggers with the receptor kinase activity a signaling cascade. The chromium-containing peptide chromodulin binds to the insulin-activated insulin receptor and optimizes its receptor kinase activity (Vincent, 2000).
In response to the insulin-initiated signaling cascade, GLUT4 (SLC2A4) moves to the plasma membrane and increases Glc uptake into insulin-stimulated cells several-fold.
Another important insulin effect is increased transcription of hepatic hexokinase 4 (glucokinase), which increases the availability of glucose 6-phosphate, the precursor for glycolysis and glycogen synthesis.
Glycolysis is further promoted by increased concentrations of the regulatory metabolite fructose 2,6-bisphosphate (due to induction of 6-phosphofructo-2-kinase, EC184.108.40.206, and lower expression of fructose-2,6-bisphosphate-2-phosphatase, EC220.127.116.11).
At the same time, gluconeogenesis is blocked by the inhibiting effect of insulin on phosphoenolpyruvate carboxykinase (EC18.104.22.168) and of fructose 2,6-bisphosphate on fructose 1,6-bisphosphatase (EC22.214.171.124).
Insulin promotes glycogenesis through increasing the availability of the glucose 6-phosphate precursor and decreasing the phosphorylation of enzymes of glycogen metabolism.
The metabolic functions of the insulin companion amylin, which tend to be in opposition to insulin action, are only beginning to be understood.
They include promotion of glycogen breakdown and inhibition of glycogen synthesis.
Years of excessive amylin secretion may be responsible for the beta cell decline in obesity and insulin resistance.
Amylin may promote the deposition of amyloid plaques (Hayden and Tyagi, 2001) and induce beta cell apoptosis (Saafi et al., 2001).
Glucagon is produced and secreted by the alpha cells of the pancreas in response to low Glc concentration.
Glucagon promotes the release of glucose 1-phosphate from glycogen.
Adrenaline and the less potently acting noradrenaline stimulate the breakdown of glycogen.
These catecholamines also counteract the inhibitory effects of non-glucose fuels on glycolysis.
Appetite and satiety: Low blood Glc concentration induces the feeling of hunger.
According to the long-held glucostatic theory, the brain, specific areas such as paraventricular and supraoptic portions of the hypothalamus, integrate input from peripheral and central Glc-responsive sensors and generate appetite sensation (Briski, 2000).
Amylin, on the other hand, is secreted in response to feeding and increased blood Glc concentration and acts on histamine H1 receptors with a significant satiety-inducing and anorectic effect (Mollet et al., 2001).
A satiety-inducing effect of insulin has also been reported, but may be weak or mediated through other effectors (such as amylin).
Postprandial metabolism: The influx of newly absorbed Glc and other nutrients alters the balance of hormonal and metabolic activities.
As outlined above, the rate of insulin (and amylin) secretion increases and the rate of glucagon decreases in response to the higher blood Glc concentration.
Gluconeogenesis is effectively turned off and glycolysis is turned on.
Glc utilization occurs in preference to fat oxidation. When high carbohydrate intake is coupled with excessive total energy intake, fat (both from diet and from adipose tissue turnover) is preferentially deposited, and the carbohydrate is used as the near-exclusive energy fuel.
Glucose fact, the release of fat from adipose tissue is slowed by the increased action of insulin.
Glucose is a reminder that both timing and quantity of carbohydrate ingestion matter.
The deposition of glycogen in liver and muscles increases, though with a considerable time lag.
Reconstitution of depleted glycogen stores is likely to take 1–2 days (Shearer et al., 2000).
Carbohydrate loading for one or more days can increase glycogen stores by a third or more (Tarnopolsky et al., 2001). Repleting glycogen stores by carbohydrate feeding on the evening before elective surgery instead of fasting appears to improve outcome and reduce hospital stays (Nygren et al., 2001).
Exercise: A burst of exertion, as in a short sprint, taxes the capacity of muscle to generate ATP for contraction.
Glycolytic breakdown of Glc to lactate is an inefficient mode of fuel utilization, because it generates only two ATP per glucose molecule.
The advantages are that glycolysis is fast, because only 11 reactions are needed, and that it operates anaerobically (i.e. does not require oxygen).
The resulting lactate moves from the muscle cell into circulation via the monocarboxylate transporter 1 (MCT1, SLC16A1). Due to the cotransport of protons, increasing acidification of the muscle cells will promote lactate export.
Lactate is used in the liver for gluconeogenesis and the resulting Glc returned to muscle for another potential round through this lactate–glucose (Cori) cycle.
Another of the many adaptations to muscle exertion is the increased activity of GLUT4, which promotes Glc influx from circulation.
Fasting and starvation: When tissue levels of Glc decline and new supplies from food are not forthcoming, the liver and kidneys begin to release Glc into circulation. Glucose Glc comes initially from glycogen stores and from the use of Glc metabolites (lactate, pyruvate, and others) for gluconeogenesis, later from tissue protein.