Lab1 - Carbohydrates Identification

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Questions and Answers

What color indicates a positive result in the Anthrone test for carbohydrates?

  • Blue-green (correct)
  • Red
  • Purple ring
  • Brown

Which test is specifically used to identify pentoses?

  • Bi al's test (correct)
  • Benedict's test
  • Seliwanoff test
  • Barfoed's test

Which of the following is the main reducing agent used in Fehling's test?

  • Coppersulfate
  • Sodium citrate
  • Cupric ion (correct)
  • Tartrate ion

How long does it typically take for ketohexoses to react in the Seliwanoff test?

<p>2 minutes (D)</p> Signup and view all the answers

What type of product is formed from the oxidation of galactose in the Mucic Acid test?

<p>Insoluble mucic acid (A)</p> Signup and view all the answers

Which test differentiates between aldohexoses and ketohexoses based on time of reaction?

<p>Seliwanoff test (A)</p> Signup and view all the answers

What indicates a positive result in the Barfoed's test?

<p>Formation of a red precipitate (B)</p> Signup and view all the answers

Which of the following carbohydrate types does the Molisch test identify?

<p>All carbohydrates (D)</p> Signup and view all the answers

What is the primary reagent used in the Benedict's test?

<p>Copper(II) sulfate (B)</p> Signup and view all the answers

Which of the following sugars is specifically identified by the Mucic Acid test?

<p>Galactose (B)</p> Signup and view all the answers

Which disaccharide is formed by the combination of glucose and galactose?

<p>Lactose (B)</p> Signup and view all the answers

What type of bond is characteristic of sugars like ribose and glucose?

<p>Covalent bond (D)</p> Signup and view all the answers

Which of the following reagents is used in the Fehling's test to identify reducing sugars?

<p>Copper(II) sulfate (C)</p> Signup and view all the answers

Which sugar is characterized as a ketone?

<p>Fructose (A)</p> Signup and view all the answers

During the Seliwanoff's test, which color indicates the presence of a ketose sugar?

<p>Purple (A)</p> Signup and view all the answers

What byproduct is formed during the mucic acid test when lactose is present?

<p>Galactose (B)</p> Signup and view all the answers

Which method can be used to identify pentoses in a sugar solution?

<p>Bial's test (B)</p> Signup and view all the answers

What characteristic change occurs in a reducing sugar during the Benedict's test?

<p>Color change to red (D)</p> Signup and view all the answers

What type of sugars are ribose and deoxyribose classified as?

<p>Monosaccharides (C)</p> Signup and view all the answers

Which sugar contains a double bond in its molecular structure?

<p>Fructose (D)</p> Signup and view all the answers

Which term correctly classifies gum based on its carbohydrate structure?

<p>Heteropolysaccharide (D)</p> Signup and view all the answers

Which of the following substances is classified as a polysaccharide?

<p>Inulin (B)</p> Signup and view all the answers

What reagent is known to oxidize reducing sugars?

<p>Tollen’s reagent (A)</p> Signup and view all the answers

Which test is predominantly employed to identify pentoses?

<p>Bial’s test (B)</p> Signup and view all the answers

What is the role of copper ions in the Benedict’s test?

<p>They reduce the sugars (A)</p> Signup and view all the answers

Which carbohydrate is an example of a monosaccharide?

<p>Galactose (D)</p> Signup and view all the answers

Which of the following compounds is considered a heteropolysaccharide?

<p>Xyloglucan (D)</p> Signup and view all the answers

What type of carbohydrate is maltose classified as?

<p>Disaccharide (B)</p> Signup and view all the answers

Which test can be used to identify reducing sugars aside from the Benedict's test?

<p>Fehling's solution (D)</p> Signup and view all the answers

Which of the following is NOT a reducing sugar?

<p>Sucrose (A)</p> Signup and view all the answers

Flashcards

Disaccharide

A carbohydrate formed by the combination of two monosaccharides.

Covalent Bond

A chemical bond formed by sharing electrons between atoms.

Monosaccharide

A simple sugar that cannot be broken down into smaller sugars.

Tollen's test

A chemical test used to identify aldehydes.

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Benedict's test

A chemical test for reducing sugars.

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Lactose

A disaccharide composed of glucose and galactose.

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Fructose

A monosaccharide, a simple sugar.

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Galactose

A monosaccharide, a simple sugar.

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Seliwanoff's test

A test for the presence of fructose.

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Bials test

A test for pentoses and furfural.

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Homopolysaccharide

A polysaccharide composed of only one type of monosaccharide.

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Heteropolysaccharide

A polysaccharide composed of more than one type of monosaccharide.

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Polysaccharide

A large carbohydrate molecule made up of many monosaccharides.

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Reducing sugar

A sugar that can reduce other substances.

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Benedict's reagent

A chemical reagent used to test for reducing sugars.

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Bial's test

A chemical test used to identify pentoses (5-carbon sugars).

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Mucic test

A test used to identify glucuronic acid.

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Inulin

A polysaccharide used as a test for polysaccharides.

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Monosaccharide

The simplest form of carbohydrate.

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Tollen's reagent

A chemical reagent used to test for aldehydes and reducing sugars.

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Molisch Test

A test to identify carbohydrates (sugars). It detects the presence of a furfural derivative formed from the sugars with sulfuric acid.

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Anthrone Test

A test used for identifying carbohydrates. It produces a blue-green color.

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Barfoed's Test

A test that distinguishes monosaccharides, specifically checking for reducing properties. it specifically tests for MONOSACCHARIDES, taking less time than the test for disaccharides.

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Seliwanoff's test

Identifies ketohexoses. This test helps in detecting the presence of ketose sugars specifically. It's faster for ketohexoses than for aldohexoses, showing red.

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Bial's Test

Identifies pentoses (5-carbon sugars). It produces a specific color change, a hint.

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Benedict's Test

Identifies reducing sugars in a solution; it determines if there's a reducing sugar present.

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Fehling's Test

Another test for reducing sugars. It leverages copper ions to detect reducing sugars.

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Mucic Acid Test

A test specifically for galactose, using nitric acid as an oxidizing agent.

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Reducing Sugar

A carbohydrate that can donate electrons to an oxidizing agent (copper ion for example); thus, the oxidizing agent is reduced.

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Carbohydrate Identification

The process of using various tests (e.g., Molisch, Benedict's, Seliwanoff's) to determine the specific type of carbohydrate present in a sample.

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Study Notes

Carbohydrate Identification

  • Carbohydrates are primarily energy sources, composed of carbon, hydrogen, and oxygen.
  • Historically, they were considered hydrates of carbon (Hâ‚‚O).
  • Classified as polyhydroxyaldehydes or polyhydroxyketones.
  • Three main classes studied: monosaccharides, oligosaccharides (disaccharides), and polysaccharides.

Monosaccharides

  • Crystalline, water-soluble compounds.
  • Simple sugars; one carbonyl group and multiple hydroxyl groups.
  • Common hexoses include glucose, fructose, and galactose; pentoses include arabinose and xylose.
  • Aliphatic aldehydes or ketones.

Oligosaccharides (Disaccharides)

  • Relatively low molecular weight polymers (2-20 monosaccharide units).
  • Covalently bonded through glycosidic linkages.
  • Examples include sucrose, lactose, and maltose.

Polysaccharides

  • High molecular weight polymers (more than 20 monosaccharide units).
  • Examples include glycogen (animal storage), starch (plant storage), cellulose (fiber), and inulin (fructose storage).
  • Homopolysaccharides: Contain only one type of monosaccharide (e.g., starch, cellulose, glycogen).
  • Heteropolysaccharides: Contain more than one type of monosaccharide (e.g., pectin, hemicellulose, gums).

Carbohydrate Nomenclature

  • Saccharide names end in -ose (e.g., glucose, fructose).
  • Names indicate the functional group (aldo- for aldehyde, keto- for ketone) and the number of carbons (e.g., aldohexose, ketohexose).

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