Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Glucose shopping experience:
1. Compare - without doubt the biggest advantage that the Glucose offers shoppers today is the ability to compare thousands of Glucose at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Glucose? Wrong! If the Glucose is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Glucose then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Glucose? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Glucose and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Glucose wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Glucose then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Glucose site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Glucose, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Glucose, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
{]|-| IUPAC nomenclature| 6-(hydroxymethyl)oxane
-2,3,4,5-tetrol|-| Synonym for D-glucose| dextrose|-One indicator test for glucose would be testing it with glucose test paper. Glucose test paper is paper that is usually orange or blue and will change color to a substance when glucose is present.| Varieties of D-glucose|
α-D-glucose;
β-D-glucose|-| Abbreviations|
Glc, CHO|-|
Chemical formula6[Hydrogen12Oxygen6|-|
Molecular mass| α-D-glucose: 146°Cβ-D-glucose: 150°C|-| [Density| 50-99-7 (D-glucose)|-| [CAS registry number| 921-60-8 (L-glucose)|-|
Simplified molecular input line entry specification| C(C1C(C(C(C(O1)O)O)O)O)O|-| Normal clinical values| blood 75-115 mg/
litre#SI prefixes applied to the litre,
urine 50-300 mg/24 hr.] (or simple
sugar), is an important
carbohydrate in biology. The living
Cell (biology) uses it as a source of energy and metabolic intermediate. Glucose is one of the main products of
photosynthesis and starts
cellular respiration in both
prokaryotes and
eukaryotes. The name comes from the Greek language word
glykys (γλυκύς), which means "sweet", plus the suffix "-ose" which denotes a
carbohydrate.
Two
stereoisomerisms of the aldohexose sugars are known as glucose, only one of which (D-glucose) is biologically active. This form (D-glucose) is often referred to as
dextrose (
dextrose monohydrate), especially in the food industry. This article deals with the D-form of glucose. The mirror-image of the molecule, L-glucose, cannot be metabolized by cells in the biochemical process known as
glycolysis.
Glucose is commonly available in the form of a white substance or as a solid crystal. It can also be commonly found as an
aqueous solution.
== Production ==
Natural
Glucose is one of the products of photosynthesis in plants and some prokaryotes.
In animals and fungi, glucose is the result of the breakdown of glycogen, a process known as glycogenolysis. In plants - the breakdown substrate is starch.
In animals, glucose is synthesized in the liver and kidneys from non-carbohydrate intermediates, such as pyruvate and glycerol, by a process known as gluconeogenesis.
Commercial
Glucose is produced commercially via the
enzyme hydrolysis of starch. Many crops can be used as the source of starch. Maize, rice, wheat,
potato, cassava,
arrowroot, and sago are all used in various parts of the world. In the United States,
cornstarch (from maize) is used almost exclusively.
This enzymatic process has two stages. Over the course of 1-2 hours near 100 °C, these enzymes hydrolyze starch into smaller carbohydrates containing on average 5-10 glucose units each. Some variations on this process briefly heat the starch mixture to 130 °C or hotter one or more times. This heat treatment improves the solubility of starch in water, but deactivates the enzyme, and fresh enzyme must be added to the mixture after each heating.
In the second step, known as "saccharification", the partially hydrolyzed starch is completely hydrolyzed to glucose using the glucoamylase enzyme from the
fungus Aspergillus niger. Typical reaction conditions are
pH 4.0–4.5, 60 °C, and a carbohydrate concentration of 30–35% by weight. Under these conditions, starch can be converted to glucose at 96% yield after 1–4 days. Still higher yields can be obtained using more dilute solutions, but this approach requires larger reactors and processing a greater volume of water, and is not generally economical. The resulting glucose solution is then purified by
filtration and concentrated in a multiple-effect evaporator. Solid D-glucose is then produced by repeated
crystallizations.
image:Glucose 1.jpg|Glucoseimage:Glucose 2.jpg|Glucose tablets
Function
We can speculate on the reasons why glucose, and not another monosaccharide such as fructose (Fru), is so widely used in evolution, the ecosystem, and metabolism. Glucose can form from formaldehyde under
abiotic conditions, so it may well have been available to primitive
biochemical systems. Probably more important to advanced life is the low tendency of glucose, by comparison to other hexose sugars, to non-specifically react with the
amino groups of
proteins. This reaction (glycation) reduces or destroys the function of many
enzymes. The low rate of glycation is due to glucose's preference for the less reactive cyclic
isomer. Nevertheless, many of the long-term complications of
diabetes (e.g., blindness, renal failure, and peripheral neuropathy) are probably due to the glycation of proteins or lipids. In contrast,
enzyme-regulated addition of glucose to proteins by
glycosylation is often essential to their function.
As an energy source
Glucose is an ubiquitous fuel in biology. It is used as an energy source in most organisms, from bacteria to humans. Use of glucose may be by either aerobic respiration or anaerobic respiration (
Fermentation (biochemistry)). Carbohydrates are the human body's key source of energy, through aerobic respiration, providing approximately 4
kilocalories (17
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 (TCAC), glucose is
oxidized to eventually form
carbon dioxide and water, yielding energy, mostly in the form of adenosine triphosphate. The insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood. A high fasting blood sugar level is an indication of prediabetic and diabetic conditions.
Glucose is a primary source of energy for the brain, and hence its availability influences psychological processes. When glucose is low,
Efortfulness psychological processes (e.g.,
self-control) are impaired.
Glucose in glycolysis
{|width=370px align=right|{{Enzymatic Reaction|foward_enzyme=Hexokinase|reaction_direction_(forward/reversible/reverse)=forward|minor_foward_substrate(s)=[Adenosine triphosphate|minor_foward_product(s)=Adenosine diphosphate|minor_reverse_substrate(s)=|minor_reverse_product(s)=|substrate_image=Glucose_wpmp.png|product_image=Glucose-6-phosphate_wpmp.png-->|-| |}
Use of glucose as an energy source in cells is via aerobic or anaerobic respiration. Both of these start with the early steps of the
glycolysis metabolic pathway. The first step of this is the phosphorylation of glucose by
hexokinase to prepare it for later breakdown to provide energy.
The major reason for the immediate phosphorylation of glucose by a hexokinase is to prevent diffusion out of the cell. The phosphorylation adds a charged
phosphate group so the glucose 6-phosphate cannot easily cross the cell membrane. Irreversible first steps of a metabolic pathway are common for regulatory purposes.
As a precursor (chemistry)
Glucose is critical in the production of proteins and in lipid metabolism. Also, in plants and most animals, it is a
precursor (chemistry) for
vitamin C (ascorbic acid) production. It is modified for use in these processes by the glycolysis pathway.
Glucose is used as a precursor for the synthesis of several important substances. starch solution Starch, cellulose, and
glycogen ("animal starch") are common glucose polymers (
polysaccharides).
Lactose, the predominant sugar in milk, is a glucose-galactose disaccharide. In
sucrose, another important
disaccharide, glucose is joined to fructose. These synthesis processes also rely on the phosphorylation of glucose through the first step of glycolysis.
Sources and absorption
All major dietary carbohydrates contain glucose, either as their only building block, as in starch and glycogen, or together with another monosaccharide, as in sucrose and lactose. In the lumen of the duodenum and small intestine, the oligo- and polysaccharides are broken down to monosaccharides by the pancreatic and intestinal glycosidases. Glucose is then transported across the apical membrane of the
enterocytes by SLC5A1, and later across their basal membrane by SLC2A2 ( ref). Some of the glucose goes directly toward fueling
brain cells and
erythrocytes, while the rest makes its way to the liver and muscles, where it is stored as glycogen, and to adipose tissue, where it can be used to power reactions which synthesize some
fats. Glycogen is the body's auxiliary energy source, tapped and converted back into glucose when there is need for energy.
See also
References
External links
- (D-glucose)
- (L-glucose)
- (D-glucose)
- (L-glucose)
- More on the chemistry and function of glucose in biology at EvoWiki
- Computational Chemistry Wiki
{]|-| IUPAC nomenclature| 6-(hydroxymethyl)oxane
-2,3,4,5-tetrol|-| Synonym for D-glucose| dextrose|-One indicator test for glucose would be testing it with glucose test paper. Glucose test paper is paper that is usually orange or blue and will change color to a substance when glucose is present.| Varieties of D-glucose|
α-D-glucose;
β-D-glucose|-| Abbreviations|
Glc, CHO|-|
Chemical formula6[Hydrogen12
Oxygen6|-|
Molecular mass| α-D-glucose: 146°Cβ-D-glucose: 150°C|-| [Density| 50-99-7 (D-glucose)|-| [CAS registry number| 921-60-8 (L-glucose)|-| Simplified molecular input line entry specification| C(C1C(C(C(C(O1)O)O)O)O)O|-| Normal clinical values| blood 75-115 mg/litre#SI prefixes applied to the litre,
urine 50-300 mg/24 hr.] (or simple sugar), is an important carbohydrate in biology. The living Cell (biology) uses it as a source of energy and metabolic intermediate. Glucose is one of the main products of photosynthesis and starts cellular respiration in both prokaryotes and eukaryotes. The name comes from the Greek language word
glykys (γλυκύς), which means "sweet", plus the suffix "-ose" which denotes a carbohydrate.
Two stereoisomerisms of the
aldohexose sugars are known as glucose, only one of which (D-glucose) is biologically active. This form (D-glucose) is often referred to as
dextrose (
dextrose monohydrate), especially in the food industry. This article deals with the D-form of glucose. The mirror-image of the molecule, L-glucose, cannot be metabolized by cells in the biochemical process known as glycolysis.
Glucose is commonly available in the form of a white substance or as a solid crystal. It can also be commonly found as an
aqueous solution.
== Production ==
Natural
Glucose is one of the products of photosynthesis in plants and some prokaryotes.
In animals and fungi, glucose is the result of the breakdown of glycogen, a process known as glycogenolysis. In plants - the breakdown substrate is starch.
In animals, glucose is synthesized in the liver and kidneys from non-carbohydrate intermediates, such as pyruvate and glycerol, by a process known as gluconeogenesis.
Commercial
Glucose is produced commercially via the
enzyme hydrolysis of
starch. Many crops can be used as the source of starch. Maize, rice,
wheat, potato,
cassava,
arrowroot, and
sago are all used in various parts of the world. In the United States,
cornstarch (from maize) is used almost exclusively.
This enzymatic process has two stages. Over the course of 1-2 hours near 100 °C, these enzymes hydrolyze starch into smaller carbohydrates containing on average 5-10 glucose units each. Some variations on this process briefly heat the starch mixture to 130 °C or hotter one or more times. This heat treatment improves the solubility of starch in water, but deactivates the enzyme, and fresh enzyme must be added to the mixture after each heating.
In the second step, known as "saccharification", the partially hydrolyzed starch is completely hydrolyzed to glucose using the
glucoamylase enzyme from the
fungus Aspergillus niger. Typical reaction conditions are
pH 4.0–4.5, 60 °C, and a carbohydrate concentration of 30–35% by weight. Under these conditions, starch can be converted to glucose at 96% yield after 1–4 days. Still higher yields can be obtained using more dilute solutions, but this approach requires larger reactors and processing a greater volume of water, and is not generally economical. The resulting glucose solution is then purified by
filtration and concentrated in a
multiple-effect evaporator. Solid D-glucose is then produced by repeated crystallizations.
image:Glucose 1.jpg|Glucoseimage:Glucose 2.jpg|Glucose tablets
Function
We can speculate on the reasons why glucose, and not another monosaccharide such as fructose (Fru), is so widely used in evolution, the ecosystem, and metabolism. Glucose can form from
formaldehyde under
abiotic conditions, so it may well have been available to primitive
biochemical systems. Probably more important to advanced life is the low tendency of glucose, by comparison to other hexose sugars, to non-specifically react with the
amino groups of proteins. This reaction (glycation) reduces or destroys the function of many
enzymes. The low rate of glycation is due to glucose's preference for the less reactive cyclic isomer. Nevertheless, many of the long-term complications of diabetes (e.g.,
blindness,
renal failure, and
peripheral neuropathy) are probably due to the glycation of proteins or lipids. In contrast, enzyme-regulated addition of glucose to proteins by
glycosylation is often essential to their function.
As an energy source
Glucose is an ubiquitous fuel in
biology. It is used as an energy source in most organisms, from bacteria to humans. Use of glucose may be by either aerobic respiration or anaerobic respiration (Fermentation (biochemistry)). Carbohydrates are the human body's key source of energy, through aerobic respiration, providing approximately 4
kilocalories (17
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 (TCAC), glucose is oxidized to eventually form carbon dioxide and
water, yielding energy, mostly in the form of adenosine triphosphate. The insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood. A high fasting blood sugar level is an indication of prediabetic and diabetic conditions.
Glucose is a primary source of energy for the brain, and hence its availability influences psychological processes. When glucose is low, Efortfulness psychological processes (e.g., self-control) are impaired.
Glucose in glycolysis
{|width=370px align=right|{{Enzymatic Reaction|foward_enzyme=Hexokinase|reaction_direction_(forward/reversible/reverse)=forward|minor_foward_substrate(s)=[Adenosine triphosphate|minor_foward_product(s)=Adenosine diphosphate|minor_reverse_substrate(s)=|minor_reverse_product(s)=|substrate_image=Glucose_wpmp.png|product_image=Glucose-6-phosphate_wpmp.png-->|-| |}
Use of glucose as an energy source in cells is via aerobic or anaerobic respiration. Both of these start with the early steps of the glycolysis
metabolic pathway. The first step of this is the phosphorylation of glucose by
hexokinase to prepare it for later breakdown to provide energy.
The major reason for the immediate phosphorylation of glucose by a
hexokinase is to prevent diffusion out of the cell. The phosphorylation adds a charged
phosphate group so the
glucose 6-phosphate cannot easily cross the cell membrane. Irreversible first steps of a metabolic pathway are common for regulatory purposes.
As a
precursor (chemistry)
Glucose is critical in the production of
proteins and in lipid metabolism. Also, in plants and most animals, it is a
precursor (chemistry) for
vitamin C (ascorbic acid) production. It is modified for use in these processes by the glycolysis pathway.
Glucose is used as a precursor for the synthesis of several important substances. starch solution Starch,
cellulose, and glycogen ("animal starch") are common glucose
polymers (polysaccharides). Lactose, the predominant sugar in milk, is a glucose-galactose disaccharide. In sucrose, another important
disaccharide, glucose is joined to fructose. These synthesis processes also rely on the phosphorylation of glucose through the first step of glycolysis.
Sources and absorption
All major dietary carbohydrates contain glucose, either as their only building block, as in starch and glycogen, or together with another monosaccharide, as in sucrose and lactose. In the lumen of the duodenum and small intestine, the oligo- and polysaccharides are broken down to monosaccharides by the pancreatic and intestinal glycosidases. Glucose is then transported across the apical membrane of the enterocytes by
SLC5A1, and later across their basal membrane by
SLC2A2 ( ref). Some of the glucose goes directly toward fueling brain cells and
erythrocytes, while the rest makes its way to the liver and
muscles, where it is stored as glycogen, and to
adipose tissue, where it can be used to power reactions which synthesize some fats. Glycogen is the body's auxiliary energy source, tapped and converted back into glucose when there is need for energy.
See also
References
External links
- (D-glucose)
- (L-glucose)
- (D-glucose)
- (L-glucose)
- More on the chemistry and function of glucose in biology at EvoWiki
- Computational Chemistry Wiki
Glucose
Because Glucose is the unit from which starch, cellulose and glycogen are made up, and because of its special role in biological processes, there are probably more glucose groups ...
Glucose Tests: At a Glance
Overview of Glucose blood test (Blood sugar, GTT, Fasting glucose, glucose tolerance tests) which diagnoses and manages diabetes by determining blood levels of glucose.
Definition: glucose from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.
Glucose - Wikipedia, the free encyclopedia
Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
Medical Glossary - NHS Direct
Glucose Glucose (or dextrose) is a type of sugar that is used by the body to produce energy. Gene Genes contain information that you inherit from your parents, such as eye or hair ...
Glucose - MOTM 2007 - Chime version
Sugar? It depends in your definition... For non-scientific use, the term 'sugar' refers to the molecule sucrose (also called "table sugar"), and these are the white crystals we add ...
Structure of the glucose molecule
Molecular structure of glucose ... Structure of carbohydrates. Glucose is an example of a carbohydrate which is commonly encountered.
Blood glucose levels
People with diabetes are unable to control their blood sugar levels without treatment. If they are allowed to stay high for a long period of time then a number of serious ...
British Nutrition Foundation
The most commonly occurring monosaccharides in food are glucose, fructose and galactose. The formula for glucose (C6H1206) is shown in Figure 1.
glucose
Simple sugar present in the blood and manufactured by green plants during photosynthesis ... Tiscali Quicklinks. Please visit our Accessibility Page for a list of the Access Keys ...
