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MBB 321 Lecture 5: Lecture 5 - Monosaccharides

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burgundyferret646

7 Oct 2015

School

Simon Fraser University

Department

Molec Biol & Biochem

Course

Professor

Ingrid Northwood

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Document Summary

Carbohydrates: polyhydroxy aldehydes or ketones that are the most abundant form of organic matter on earth. There are three major classes of carbohydrates: monosaccharides, disaccharides, and polysaccharides. Monosaccharides: also known as simple sugars, consist of a single polyhydroxy aldehyde or ketone unit, with the. A monosaccharide can be either a polyhydroxy-aldehyde known as an aldose (contains carbonyl group at the end. Of the carbon chain), or a polyhydroxy-ketone known as a ketose (contains carbonyl group within the carbon. Aldoses and ketoses lack an asymmetric center at the top and bottom carbons, and all ketoses contain a carbonyl. Group within the carbon chain and therefore lack an additional asymmetric center and thus have half the number of stereoisomers. Centers in the ketose form: hexoses: a six carbon monosaccharide which contains 4 chiral centers in the aldose form and 3 chiral. General rule: a molecule with n chiral centers will have 2n stereoisomers: monosaccharide stereochemistry.

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Related Questions

Biochemistry. All the answers please

21- Which of these statements is false? A.The Benedict's test allows us to detect the presence of reducing sugars B. The Benedict's test allows us to detect the presence of sugars with a free aldehyde or ketone C. All monosaccharides are reducing sugars because they all have a free reactive carbonyl group. D. All disaccharides have exposed carbonyl groups and are also reducing sugars. E. Sucrose and starches are non-reducing sugars and will not react with Benedict's solution. 22-Select the incorrect statement below about Fehling's test A. Fehling's test is specifically a test for carbohydrates, thus explaining its extensive use itn carbohydrate chemistry B. A positive Fehling's test result is indicated by the formation of a brick red precipitate. C. Fehling's test takes advantage of the ready reactivity of aldehydes by using the weak oxidizing agent cupric ion (Cu2+) in alkaline solution D. In addition to the copper ion, Fehling's solution contains tartrate ion as a complexing agent in the form of copper(II) D-tartrate to keep the copper ion in solution. E. Fehling's reagent is commonly used for reducing sugars but is not specific for aldehydes. F Glucose is a reducing sugar that reacts with Fehling's reagent to form an orange to red precipitate. 23 Select the incorrect statement below about Benedict's test A. Benedict's test can be used to determine the presence of glucose in urine. B. The amount of cuprous oxide formed in Benedict's test is proportional to the amount of reducing sugar present in the urine. C. In Benedict's test, low to moderate levels of reducing sugar turn the solution green; solutions with high glucose levels turn Benedict's yellow or brick red D. Tests using the enzyme glucose oxidase are more specific for glucose than the Benedict's or Fehling's test. E. none of the above 24. Select the incorrect statement below A. Sugars that contain aldehyde groups that are oxidised to carboxylic acids are classified as reducing sugars B. Reducing sugars reduce the Cu2+ in Benedict's solution to Cut which forms as a red precipitate, copper (I) oxide. C. Any sugar that contains a hemi-acetal will be a reducing sugar D. Glycosides are acetals and therefore reducing sugars. E Because the acetals of monosaccharides can undergo mutarotation or oxidation, this means that acetals are nonreducing sugars. F. Fructose (though a ketone) is also a reducing sugar because in the open-chain form, a rearrangement between the hydroxyl group on carbon 1 and the ketone group provides an aldehyde group that can be oxidized. 25. Select the best answer from those below. A. Clinitest is an implementation of the 'Benedict test for reducing sugars. B. Clinitest measures the reducing end concentration of all reducing sugars by comparison with a color charts. C. Clinitest percentage readings are referenced to glucose so that a 1% reducing sugar glucose equivalent corresponds with a 1 gram glucose per 100ml of water concentration. D. All the above are correct