Most of the chemical compounds presentin living organisms contain skeletons of covalently bonded carbon atoms(C-C-C-C). These compounds are known as organic compounds, because mostof these are either present in, or produced by living things. Organic compoundsare the major components of cells and tissues. They provide energy forlife processes, participate in and regulate metabolic reactions, and transmitinformation. Organic macromolecules in living organisms can be classifiedas either carbohydrates, proteins, lipids, or nucleic acids,among others. These macromolecules are always made of smaller subunits.The subunits of macromolecules are held together with covalent bonds, andhave different structures and properties. For example, lipids made of fattyacids have many C-H bonds and relatively little oxygen, while proteinsmade of amino acids have amino groups (-NH2) and carboxyl (-COOH)groups. These characteristic groups impart different chemical propertiesto macromolecules--for example, monosaccharides such as glucose are polarand soluble in water, while lipids are nonpolar and insoluble in water. Carbohydrates are compounds that containcarbon, hydrogen and oxygen. Carbohydrates include a variety of compounds,such as sugars, starches, and celluloses. While sugars and starches serveas energy sources for cells; celluloses are structural components of thewalls that surround plant cells. The term carbohydrate literally means"hydrated (H20) carbon" Carbohydrates may contain one sugarmolecule (monosaccharides), two sugar molecules (disaccharides), or manysugar units (polysaccharides). In this lab, we will be concerned with thenature and activities of the carbohydrates and with their structure. Note:structure dictates how the carbohydrate will react under certain conditions. Since Continue reading >>
Benedict's Test- Principle, Composition, Preparation, Procedure And Result Interpretation
Benedicts Test- Principle, Composition, Preparation, Procedure and Result Interpretation 4.3/5 (602) Benedicts Test- Principle, Composition, Preparation, Procedure and Result Interpretation Benedicts Test is used to test for simple carbohydrates.The Benedicts test identifies reducing sugars (monosaccharides and some disaccharides), which have free ketone or aldehyde functional groups.Benedicts solution can be used to test for the presence ofglucose in urine. Some sugars such as glucose are called reducing sugars because they are capable of transferring hydrogens (electrons) to other compounds, a process called reduction. When reducing sugars are mixed with Benedicts reagent and heated, a reduction reaction causes the Benedicts reagent to change color. The color varies from green to dark red (brick) or rusty-brown, depending on the amount of and type of sugar. Benedicts quantitative reagent contains potassium thiocyanate and is used to determine how much reducing sugar is present. This solution forms a copper thiocyanate precipitate which is white and can be used in a titration. The titration should be repeated with 1% glucose solution instead of the sample for calibration When Benedicts solution and simple carbohydrates are heated, the solution changes to orange red/ brick red. This reaction is caused by the reducing property of simple carbohydrates. The copper (II) ions in the Benedicts solution are reduced to Copper (I) ions, which causes the color change. The red copper(I) oxide formed is insoluble in water and is precipitated out of solution. This accounts for the precipitate formed.As the concentration of reducing sugar increases, the nearer the final colour is to brick-red and the greater the precipitate formed.Sometimes a brick red solid, copper oxide, precipita Continue reading >>
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Qualitative Analysis Of Carbohydrates (theory) : Biochemistry Virtual Lab I : Biotechnology And Biomedical Engineering : Amrita Vishwa Vidyapeetham Virtual Lab
This forms the reduction test of carbohydrates. Fehlings solution contains blue alkaline cupric hydroxide solution, heated with reducing sugars gets reduced to yellow or red cuprous oxide and is precipitated. Hence, formation of the yellow or brownish-red colored precipitate helps in the detection of reducing sugars in the test solution. As in Fehlings test, free aldehyde or keto group in the reducing sugars reduce cupric hydroxide in alkaline medium to red colored cuprous oxide. Depending on the concentration of sugars, yellow to green color is developed . All monosaccharides are reducing sugars as they all have a free reactive carbonyl group. Some disaccharides, like maltose, have exposed carbonyl groups and are also reducing sugars, but less reactive than monosaccharides Barfoed's test is used to detect the presence of monosaccharide (reducing) sugars in solution. Barfoed's reagent, a mixture of ethanoic (acetic) acid and copper(II) acetate, is combined with the test solution and boiled. A red copper(II) oxide precipitate is formed will indicates the presence of reducing sugar. The reaction will be negative in the presence of disaccharide sugars because they are weaker reducing agents. This test is specific for monosaccharides . Due to the weakly acidic nature of Barfoed's reagent, it is reduced only by monosaccharides. It is a color reaction specific for ketoses. When conce: HCl is added. ketoses undergo dehydration to yield furfural derivatives more rapidly than aldoses. These derivatives form complexes with resorcinol to yield deep red color. The test reagent causes the dehydration of ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural reacts with resorcinol present in the test reagent to produce a red product within two minutes (reaction not sho Continue reading >>
What Is Benedict's Test For Reducing Sugars?
Benedict's Test for non-reducing Sugars is a test which determines the presence of non-reducing sugars in a test solution. The principal reagent in Benedict's Test for Reducing Sugars is Benedict's Solution which contains copper(II) sulphate sodium carbonate sodium citrate Sugars are classified as reducing or non-reducing based on their ability to act as a reducing agent during the Benedict's Test. A reducing agent donates electrons during a redox reaction and is itself oxidized. The aldehyde functional group is the reducing agent in reducing sugars. Reducing sugars have either an aldehyde functional group or have a ketone group - in an open chain form - which can be converted into an aldehyde. Reducing sugars are simple sugars and include all monosaccharides and most disaccarides. Some examples of monosaccharides are glucose, fructose and galactose.Examples of reducing disaccharides are lactose and maltose. Note that the disaccharide sucrose is not a reducing sugar. In fact, sucrose is the most common non-reducing sugar. The test may be qualitative, or it may be quantitative. The qualitative test produces a colour change from blue to green to yellow to orange to brick red. The qualitative test is also regarded as semi-quantitative as the colour obtained correlates to the concentration of reducing sugars in the solution ( see observations below). This allows for a rough estimation of the amount of reducing sugar present. The qualitative test is discussed here. The quantitative test involves the use of potassium thicyanate and the production of copper thiocyanate as white or pale green precipitate. This precipitate can then be titrated. A liquid food sample does not need prior preparation except dilution if viscous or concentrated. For a solid sample prepare a test solut Continue reading >>
"Carbohydrates" are chemically defined as "polyhydroxy aldehyde or polyhydroxy ketones or complex substances which on hydrolysis yield polyhydroxy aldehyde or polyhydroxy ketone." Carbohydrates are one of the fundamental classes of macromolecules found in biology. Carbohydrates are commonly found in most organisms, and play important roles in organism structure, and are a primary energy source for animals and plants. Most carbohydrates are sugars or composed mainly of sugars. By far, the most common carbohydrate found in nature is glucose, which plays a major role in cellular respiration and photosynthesis. Some carbohydrates are for structural purposes, such as cellulose (which composes plants' cell walls) and chitin (a major component of insect exoskeletons). However, the majority of carbohydrates are used for energy purposes, especially in animals. Carbohydrates are made up of a 1:2:1 ratio of Carbon, Hydrogen, and Oxygen (CH2O)n These are used only for energy in living organisms. Simple carbohydrates are also known as "Monosaccharides".The chemical formula for all the monosaccharides is CnH2nOn. They are all structural isomers of each other. There are two main types of monosaccharides. The first type are aldoses, containing an aldehyde on the first carbon, and the second type are ketoses, which have a ketone on the second carbon (This carbonyl group is always located on the second carbon). Name Formula Aldoses Ketoses Trioses C3 H6 O3 Glycerose Dihydroxyacetone Tetroses C4 H8 O4 Erythrose Erythrulose Pentoses C5 H10 O5 Ribose Ribulose Hexoses C6 H12 O6 Glucose Fructose Heptose C7 H14 O7 Glucoheptose Sodoheptulose The suffix -oses is kept for the aldoses & the suffix -uloses is kept for the ketoses. Except fructose ketoses are as common as aldoses.The most abundant m Continue reading >>
Bbc Bitesize - National 4 Chemistry - Everyday Consumer Products - Revision 1
Plants are a source of carbohydrates and oils which can be used for food, fuel and many everyday products. Carbohydrates are compounds which contain the elements carbon, hydrogen and oxygen. Plants make compounds called carbohydrates which have a wide variety of uses including foods and fuels. All carbohydrates contain the elements carbon, hydrogen and oxygen. Two of the most common carbohydrates are glucose and starch. Glucose (C6H12O6) is a simple sugar unit. From the formula, you can see that it contains twice as many hydrogen atoms as carbon atoms. Starch is a much larger, more complicated molecule. Plants produce glucose during the process of photosynthesis and convert it into starch to store energy. Starch is made by joining together many glucose units. A test to distinguish starch from glucose is to shine a beam of light through 'solutions' of each. This is also called the Tyndall Beam Effect. Dispersal only happens in starch as the large starch molecules are big enough to affect the light. This is a physical test. A chemical test for starch is to add iodine solution (yellow/brown) and look for a colour change. In the presence of starch, iodine turns a blue/black colour. It is possible to distinguish starch from glucose (and other carbohydrates) using this iodine solution test. For example, if iodine is added to a peeled potato then it will turn black. Benedicts reagent can be used to test for glucose. The test involves heating a solution of the sugar to be tested with Benedicts reagent and observing the colour change of blue to orange. Benedicts reagent will give a positive test result for glucose but not for starch. During digestion starch is broken down into glucose. Glucose is small enough to pass through the gut wall but starch cannot. This is done in the b Continue reading >>
Carbohydrates (also called saccharides) are molecular compounds made from just three elements: carbon, hydrogen and oxygen. Monosaccharides (e.g. glucose) and disaccharides (e.g. sucrose) are relatively small molecules. They are often called sugars. Other carbohydrate molecules are very large (polysaccharides such as starch and cellulose). Carbohydrates are: a source of energy for the body e.g. glucose and a store of energy, e.g. starch in plants building blocks for polysaccharides (giant carbohydrates), e.g. cellulose in plants and glycogen in the human body components of other molecules eg DNA, RNA, glycolipids, glycoproteins, ATP Monosaccharides Monosaccharides are the simplest carbohydrates and are often called single sugars. They are the building blocks from which all bigger carbohydrates are made. Monosaccharides have the general molecular formula (CH2O)n, where n can be 3, 5 or 6. They can be classified according to the number of carbon atoms in a molecule: n = 3 trioses, e.g. glyceraldehyde n = 5 pentoses, e.g. ribose and deoxyribose ('pent' indicates 5) n = 6 hexoses, e.g. fructose, glucose and galactose ('hex' indicates 6) There is more than one molecule with the molecular formula C5H10O5 and more than one with the molecular formula C6H12O6. Molecules that have the same molecular formula but different structural formulae are called structural isomers. Glyceraldehyde's molecular formula is C3H6O3. Its structural formula shows it contains an aldehyde group (-CHO) and two hydroxyl groups (-OH). The presence of an aldehyde group means that glyceraldehyde can also be classified as an aldose. It is a reducing sugar and gives a positive test with Benedict's reagent. CH2OHCH(OH)CHO is oxidised by Benedict's reagent to CH2OHCH(OH)COOH; the aldehyde group is oxidised to Continue reading >>
A Comparison Of Diagnostic Tests For Lactose Malabsorption - Which One Is The Best?
A comparison of diagnostic tests for lactose malabsorption - which one is the best? 1Department of Medicine, Innlandet Hospital Trust, Gjvik, Norway 2Unit for Applied Clinical Research, Norwegian University of Science and Technology, Trondheim, Norway 1Department of Medicine, Innlandet Hospital Trust, Gjvik, Norway 2Unit for Applied Clinical Research, Norwegian University of Science and Technology, Trondheim, Norway Received 2009 Jun 27; Accepted 2009 Oct 31. Copyright 2009 Hovde and Farup; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article has been cited by other articles in PMC. Perceived milk intolerance is a common complaint, and tests for lactose malabsorption (LM) are unreliable. This study assesses the agreement between diagnostic tests for LM and describes the diagnostic properties of the tests. Patients above 18 years of age with suspected LM were included. After oral intake of 25 g lactose, a combined test with measurement of serum glucose (s-glucose) and hydrogen (H2) and methane (CH4) in expired air was performed and symptoms were recorded. In patients with discrepancies between the results, the combined test was repeated and a gene test for lactose non-persistence was added. The diagnosis of LM was based on an evaluation of all tests. The following tests were compared: Increase in H2, CH4, H2+CH4 and H2+CH4x2 in expired air, increase in s-glucose, and symptoms. The agreement was calculated and the diagnostic properties described. Sixty patients were included, seven (12%) had LM. The agreement (kappa-values) between the methods varied fro Continue reading >>
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What Test Could Be Use To Differentiate Lactose And Glucose?
What test could be used to differentiate between sucrose and maltose? What test could be used to differentiate between sucrose and maltose? Would you like to merge this question into it? already exists as an alternate of this question. Would you like to make it the primary and merge this question into it? Benedict's test - from a clear blue solution to a cloudy rust/brown solution. Maltose and Lactose are "Reducing Sugar's" in solution with Benedict's Reagent, while sucrose is not. Sucrose is made by the glosidic linkage between glucose and fructose whereas maltose is made by the glycosidic linkage between two glucose molecules. the first figure is maltose and second is sucrose(courtesy google images) (MORE) What test could be use to differentiate lactose and glucose? take solution of substance in one test tube; in another test tube take acetic acid, water and phenyl hydrazine in 1:2:1 ratio. mix the solution of both test tubes and heat at water bath. if precipitates form immediately--> its glucose; if precipitates form after long heating--> its lactose. (MORE) Maltose will give a positive Benedict's Test (Orange colour) while, Sucrose will give a negative Benedict's Test (Aqua colour) Chemical test used to differentiate between cellulose and starch? Starch tests positive with Iodine (blue black) as due to the helical shape of amylose (a constituent of starch) it can form poly-iodide with iodine to give a positive result. Cellulose has straight chains that are joined by cross links and H bonds to form bundles, resulting in a negative result with iodine. (MORE) Continue reading >>
Fehling's Test For Reducing Sugars
In this test the presence of aldehydes but not ketones is detectedby reduction of the deep blue solution of copper(II) to a red precipitateof insoluble copper oxide. The test is commonly used for reducing sugars but isknown to be NOT specific for aldehydes. For example, fructose gives a positive testwith Fehling's solution as does acetoin. Fehling's "A" uses 7 g CuSO4.5H2Odissolved in distilled water containing 2 drops of dilutesulfuric acid. Fehling's "B" uses 35g of potassium tartrate and 12g of NaOH in100 ml of distilled water. These two solutions should be stoppered and stored until needed. Mix 15 ml of solution-"A" with 15 ml of solution-"B" Add 2 ml of this mixture to an empty test tube. Add 3 drops of the compound to be tested to the tube. A positive test is indicated by a green suspension and a redprecipitate. The test is sensitive enough that even 1 mg of glucose will produce the characteristic red colour of the compound. The structure of copper(II) D-tartrate has been determined to be: C.K. Prout, J.R. Carruthers and F.J.C. Rossotti J. Chem. Soc. A, 3336, 1971. A variation of this is called Benedict's solution. This makes use of a single solution of copper(II) citrate which doesnot deteriorate as quickly on standing. It is prepared by taking 8.7 g of crystallised sodium citrate and5 g anhydrous sodium carbonate in about 35 cm3 of water. It may be necessary to filter. To this is added 0.87 g of crystallised copper(II) sulfate in 5 cm3 of water and the mixture made up to 50 cm3 of water. The resulting solution should be clear, otherwise filter it. The test again is to observe the reduction of the blue copper(II)solution to the red cuprous oxide. Use 5 cm3 of Benedict'ssolution and 0.4 cm3 of a 2 per cent solution of the carbohydrate.Boil for 2 minutes and allow Continue reading >>
These are complex, carbon-containing molecules associated with living organisms. Most also contain hydrogen and oxygen. There are five major types: carbohydrates, lipids, proteins, nucleic acids, and vitamins. We covered the first three types in lab. A review of our carbohydrate test data is provided on this page. Click the molecule types above to link to the associated review material. Benedict's Reagent: A Test for Reducing Sugars Carbohydrates are divided into two groups based on the complexity of their structure. Simple carbohydrates can form either a single ring structure (monosaccharides) or a double ring structure (disaccharides -- formed when a pair of monosaccharides bond). Simple carbohydrates include familiar sugars such the monosaccharides glucose (the basic fuel of cells) and fructose (found in fruits). Common disaccharides include sucrose (table sugar) and lactose (the sugar in milk). Complex carbohydrates (polysaccharides) are chains of many bonded simple carbohydrates, and are often used for energy storage. These include starch, cellulose, and glycogen. One test for the presence of many simple carbohydrates is to use Benedict's reagent. It turns from turquoise to yellow or orange when it reacts with reducing sugars. These are simple carbohydrates with unbound aldehyde or ketone groups. In lab, we used Benedict's reagent to test for one particular reducing sugar: glucose. Benedict's reagent starts out aqua-blue. As it is heated in the presence of reducing sugars, it turns yellow to orange. The "hotter" the final color of the reagent, the higher the concentration of reducing sugar. In general, blue to blue-green or yellow-green is negative, yellowish to bright yellow is a moderate positive, and bright orange is a very strong positive. (See below). 2: Bene Continue reading >>
"Benedict's" redirects here. For other uses, see Benedict (disambiguation). Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent named after American chemist Stanley Rossiter Benedict. It is a complex mixture of sodium carbonate, sodium citrate and copper(II) sulfate pentahydrate. It is often used in place of Fehling's solution to detect the presence of reducing sugars. The presence of other reducing substances also gives a positive reaction. Such tests that use this reagent are called the Benedict's tests. A positive test with Benedict's reagent is shown by a color change from clear blue to a brick-red precipitate. Generally, Benedict's test detects the presence of aldehydes and alpha-hydroxy-ketones, also by hemiacetal, including those that occur in certain ketoses. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha-hydroxy-ketone, and gives a positive test because it is converted to the aldoses glucose and mannose by the base in the reagent. The principle of Benedict's test is that when reducing sugars are heated in the presence of an alkali they are converted to powerful reducing species known as enediols. Enediols reduce the cupric compounds (Cu2+) present in the Benedict's reagent to cuprous compounds (Cu+) which are precipitated as insoluble red copper(I) oxide(Cu2O). The color of the obtained precipitate gives an idea about the quantity of sugar present in the solution, hence the test is semi-quantitative. A greenish precipitate indicates about 0.5 g% concentration; yellow precipitate indicates 1 g% concentration; orange indicates 1.5 g% and red indicates 2 g% or higher concentration. Benedict's test To test for the presence of monosaccharides and reducing d Continue reading >>
Fehling Test | Chemdemos
Fehling's reagent, a blue colored basic solution of bistartratocuprate(II) complex, is added to three different aqueous sugar solutions immersed in beakers of warm water. A brick-red precipitate forms in the solutions containing glucose and fructose. There is no reaction in the test tube containing sucrose solution. This demo is appropriate for use in an organic chemistry or biochemistry course when the reactions of carbohydrates are being studied. The fructose reaction could also be used earlier in an organic chemistry course as an illustration of a reaction that proceeds via a pathway that relies upon keto-enol tautomerism. This demo can easily be scaled up for visibility if video projection is unavailable in the classroom. One day of lead time is required for this project. Fehling's solutionis used as a chemical test used to differentiate between water-soluble aldehyde and ketone functional groups , and as a test for monosaccharides. The test was developed by German chemist Hermann von Fehling in 1849. [1 ] Fehling's solution is always prepared fresh in the laboratory. It is made initially as two separate solutions, known as Fehling's A and Fehling's B. Fehling's A is a blue aqueous solution of copper(II) sulfate pentahydrate crystals, while Fehling's B is a clear solution of aqueous potassium sodium tartrate (also known as Rochelle salt) and a strong alkali (commonly sodium hydroxide ). Equal volumes of the two mixtures are mixed together to get the final Fehling's solution, which is a deep blue colour. In this final mixture, aqueous tartrate ions from the dissolved Rochelle salt chelate to Cu2+(aq) ions from the dissolved copper sulfate crystals, as bidentate ligands giving the bistartratocuprate(II) complex as shown in the accompanying illustration. Fehling's can Continue reading >>
Sugars: The Difference Between Fructose, Glucose And Sucrose
29/06/2016 7:43 AM AEST | Updated 15/07/2016 12:56 PM AEST Sugars: The Difference Between Fructose, Glucose And Sucrose We're not just confused, we're also misinformed. "Fructose is the worst for you." "No way, sucrose is the devil." "I don't eat any sugar." Sugar is confusing. While some people only use certain types of sugars, others dismiss them completely. But is this necessary, or even grounded? To help settle the confusion, we spoke to Alan Barclay -- accredited practising dietitian, spokesperson for the Dietitians Association of Australia and Chief Scientific Officer at the Glycemic Index Foundation . "All the sugars are used as a source of fuel, but there are subtle differences in the way they are digested and absorbed," Barclay said. "In foods in Australia, the most common sugars are monosaccharides (glucose, fructose and galactose), but mostly these are occurring as disaccharides (which are sucrose, lactose and maltose)." Monosaccharides and disaccharides are two kinds of simple sugars, which are a form of carbohydrate. Oligosaccharides and polysaccharides, on the other hand, contain more sugar combinations and are known as complex carbohydrates -- for example, whole grain breads, brown rice and sweet potatoes. Monosaccharides require the least effort by the body to break down, meaning they are available for energy more quickly than disaccharides. "Monosaccharides don't require any digestion and can be absorbed into the mouth," Barclay said. "The problem there is they can cause dental caries which is one of the primary reasons why we need to be careful of how much added sugar we're consuming." Glucose -- the body's main source of energy and is found in fruit such as pasta, whole grain bread, legumes and a range of vegetables. Fructose -- this 'fruit sugar' fo Continue reading >>
Qualitative And Quantitative Tests For Carbohydrates
Qualitative and Quantitative Tests for Carbohydrates Read this article to learn about the qualitative and quantitative tests for carbohydrates. One of the most important constituents in our food is glucose which we usually obtain in the form of starch from plant sources. In our body glucose is readily utilized or is stored as glycogen. The metabolic processes in our body are mainly centred on glucose, which is a member of a large class of organic compounds called carbohydrates. These are generally referred to as sugars. Carbohydrates contain C, H and O atoms. Usually, H and O are present in the ratio of 2:1, just as in water; hence the name carbohydrates are in use. Carbohydrates in general have either an aldehyde group (as in glucose) or a keto group (as in fructose). Those containing an aldehyde group (as in glucose) are called as aldoses and those containing keto groups are called ketoses. They may also be referred to on the basis of the number of carbon atoms contained in them; for example, both glucose and fructose are hexoses as they have six carbon atoms in them. Ribose and deoxyribose are pentoses because they have five carbon atoms. Both of them are, however, aldoses. Similarly, arabinose is an aldopentose. They are also trioses, tetroses, heptoses, etc. Some carbohydrates are formed by the combination of two sugars for instance; the common sugar sucrose contains both glucose and fructose. Therefore, sucrose is referred to as a disaccharide, whereas glucose and fructose are monosaccharides. There are many disaccharides like sucrose, e.g., maltose (glucose + glucose), lactose (galactose + glucose) and so on. Most of the tests of the carbohydrates are based on their reducing properties (due to the presence of reducing aldehyde or ketone groups). Fehlings test, b Continue reading >>