Biochemistry Chapter: Disaccharides and Fermentation

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Questions and Answers

What color indicates the presence of reducing sugars in a sample solution?

Bright yellow

Colorless

Mahogany red (correct)

Deep blue

Which interaction is represented by the formation of osazones?

Reducing sugars with phenylhydrazine (correct)

Amino acids with phenylhydrazine

Reducing sugars with iodine

Non-reducing sugars with glucose

Which of the following osazones is formed from fructose?

Phenylglucosazone

Phenylfructosazone (correct)

Phenylmaltosazone

Phenyllactosazone

What color do starches produce when reacted with iodine solution?

Deep blue-black Signup and view all the answers

Which of the following sugars does not show color when tested with iodine?

Glucose Signup and view all the answers

Which sugars are produced from the hydrolysis of starch?

D-glucose and dextrins Signup and view all the answers

What is the major product of sugar fermentation by yeast?

Ethanol Signup and view all the answers

Regarding osazones, which characteristic best distinguishes reducing disaccharides from monosaccharides?

Crystallization time and shape Signup and view all the answers

Which of the following tests is used to indicate the presence of reducing sugars?

Benedict's Test Signup and view all the answers

What is the expected product of the hydrolysis of sucrose?

Fructose and Glucose Signup and view all the answers

Which principle explains the solubility behavior of lipids in different solvents?

Like Dissolves Like Principle Signup and view all the answers

What is tested by the acrolein test?

Presence of Glycerol Signup and view all the answers

Which compound is formed during the fermentation of glucose?

Ethanol and Carbon Dioxide Signup and view all the answers

In Barfoed's test, which type of sugar reacts more rapidly?

Monosaccharides Signup and view all the answers

What result indicates the presence of lipids in the grease-spot test?

Translucent Stain on Paper Signup and view all the answers

What component does hydrolysis of lactose yield?

Galactose and Glucose Signup and view all the answers

What is the primary indication of a positive Molish test?

Formation of violet ring Signup and view all the answers

Which of the following is a characteristic of reducing sugars when tested with Benedict's solution?

They cause a brick red precipitate Signup and view all the answers

Which carbohydrate tested does NOT show a positive result in Benedict's test?

Sucrose Signup and view all the answers

During the Molish test, what role does alpha-naphtol play in the reaction?

It acts as a dehydrating agent Signup and view all the answers

How does the structure of a reducing sugar differ from that of a ketone in the context of Benedict's test?

Reducing sugars have an aldehyde group, whereas ketones do not Signup and view all the answers

Which of the following carbohydrate types will not give a positive result in the Barfoed's test?

Non-reducing disaccharides Signup and view all the answers

What causes the brick red precipitate in Benedict's test?

Reduction of copper(II) ions Signup and view all the answers

What is the primary use of Benedict's solution in the context of carbohydrate testing?

Detecting reducing sugars Signup and view all the answers

Study Notes

Disaccharides and Fermentation

Disaccharides, like sucrose and lactose, need to be broken down into monosaccharides before fermentation can occur.
This breakdown happens through hydrolysis, where a water molecule is added to the disaccharide.
Sucrose hydrolysis produces glucose and fructose.
Lactose hydrolysis produces glucose and galactose.
Enzymes sucrase and lactase act as catalysts for sucrose and lactose hydrolysis, respectively.

Monosaccharide Fermentation

Monosaccharides like glucose, fructose, and galactose all have the molecular formula C6H12O6.
These monosaccharides ferment using yeast to produce ethanol and carbon dioxide.

Solubility Test

Oil is miscible in chloroform but immiscible in ethanol and water.
This follows the principle of "like dissolves like," where substances with similar polarities are more likely to mix.

Grease-Spot Test

Water is absorbed by paper, while oil forms a translucent spot.

Acrolein Test

Indicates the presence of glycerol, a component of fats and oils.
Glycerol is dehydrated to form acrolein (acrylic aldehyde) with a characteristic burned copra odor when heated with KHSO4 (catalyst).

Sterol Test

Sterols are hydroxyl derivatives of steroids (cyclopentanoperhydrophenanthrene).

Molish Test

Detects carbohydrates by forming a violet ring when an acidic solution reacts with carbohydrates.
This color is due to the interaction of the aldehyde with alpha-naphthol.
Glucose, maltose, and starch all test positive for this reaction.

Benedict's Test

Detects reducing sugars like glucose, fructose, and maltose.
It uses copper(II) sulfate (CuSO4) which is reduced to red copper(I) oxide (Cu2O) by aldehydes, oxidizing them to carboxylic acids.
The copper(I) oxide forms a brick red precipitate.
Glucose, fructose, and galactose all test positive for this reaction.

Osazone Formation

When a reducing sugar is heated with phenylhydrazine, a yellow precipitate called osazones is formed.
Osazones are used to compare the structures of sugars due to their unique crystalline forms.
The osazones of monosaccharides (glucose & fructose) form quickly and have similar needle-shaped crystals under the microscope.
Disaccharides (maltose & lactose) form osazones more slowly and have distinct crystal shapes under the microscope.

Hydrolysis of Starch and Glycogen

Iodine test for polysaccharides: iodine dissolved in an aqueous solution of potassium iodide (IKI) reacts with starch producing a deep blue-black color.
Starch and glycogen both react with IKI to produce blue-black color.
The degree of blue-black color is also dependent on the length of the chains of the polysaccharide molecules.

Fermentation of Sugars

Sugar fermentation using yeast results in the production of ethanol and carbon dioxide.
The fermentation of sucrose produces 4 molecules of ethanol and 4 molecules of carbon dioxide.
Lactose is also C12H22O11 but the atoms are arranged differently.

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Description

Explore the fascinating world of disaccharides and their role in fermentation. This quiz covers the breakdown of disaccharides like sucrose and lactose, the fermentation process of monosaccharides, and tests for solubility. Gain a deeper understanding of essential biochemical processes!