Carbohydrate Chemistry Quiz

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Questions and Answers

What type of glycosidic linkage is found in the linear polymer of β-D-fructose units?

β(2,1) linkage (correct)
β-1,4 glycosidic linkage
α-1,4 glycosidic linkage
α(2,1) linkage

Human digestion can fully metabolize the polysaccharides formed from β-glucose units.

False (B)

What is a primary use of dietary fibers in the human body?

preventing constipation

Incomplete hydrolysis of dietary fibers results in the production of ______.

cellobiose Signup and view all the answers

Match the following polysaccharides/disaccharides with their properties or uses:

Cellulose = Cannot be digested by humans Cellobiose = Produced from partial hydrolysis of cellulose Inulin = Dietary fiber with medical uses Sucrose = Common table sugar that can be digested Signup and view all the answers

Which of the following enzymes can hydrolyze sucrose?

Invertase (B) Signup and view all the answers

Sucrose is a reducing sugar.

False (B) Signup and view all the answers

What two monosaccharides make up sucrose?

Glucose and Fructose Signup and view all the answers

Raffinose is a trisaccharide made of galactose, glucose, and ______.

Fructose Signup and view all the answers

Which polysaccharide is primarily made up of glucose units?

Starch (B) Signup and view all the answers

Match the following polysaccharides to their descriptions:

Sucrose = A non-reducing disaccharide Raffinose = A trisaccharide composed of three different monosaccharides Inulin = A fructosan Glycogen = A storage form of glucose in animals Signup and view all the answers

Heteropolysaccharides are formed from two or more different monosaccharides.

True (A) Signup and view all the answers

What is the primary result of hydrolyzing cellulose?

Glucose units Signup and view all the answers

What is produced when the aldehyde group of glucose is oxidized with a mild oxidizing agent?

Gluconic acid (A) Signup and view all the answers

Galacturonic acid is derived from glucose through the oxidation of the last -CH2OH group.

False (B) Signup and view all the answers

What type of linkage connects the glucose units in maltose?

α, 1-4 glycosidic linkage Signup and view all the answers

The oxidation of both the aldehyde group and the last -CH2OH group results in the formation of __________ acid.

saccharic Signup and view all the answers

Match the following sugar acids with their correct source or oxidation type:

Gluconic acid = From glucose by oxidizing aldehyde group Galacturonic acid = From galactose by oxidizing -CH2OH group Mucic acid = From galactose by strong oxidizing agent Aldaric acid = From glucose via oxidation of both aldehyde and last -CH2OH groups Signup and view all the answers

Which of the following is NOT a reducing disaccharide?

Sucrose (C) Signup and view all the answers

Cellobiose consists of two α-glucose units linked together.

False (B) Signup and view all the answers

What is a characteristic feature of reducing sugars?

Free aldehyde or ketone group Signup and view all the answers

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Study Notes

Sugars

Sucrose is naturally dextro-rotatory but hydrolyzes to a levo-rotatory mixture of glucose and fructose.
Sucrose is also known as invert sugar.
Sucrose is formed from α-glucose and β-fructose by α,1-β,2 glycosidic linkage.
Sucrose occurs in most fruits and vegetables.

Oligosaccharides

Trisaccharides contain 3 monosaccharide units.
Tetrasaccharides contain 4 monosaccharide units.
Raffinose is a trisaccharide composed of galactose, glucose, and fructose.
Stachyose is a tetrasaccharide composed of 2 galactose molecules, glucose, and fructose.

Polysaccharides

Polysaccharides are polymers of more than 10 monosaccharide residues united by glycosidic linkages.
Homopolysaccharides (homogenous) yield the same type of monosaccharide units on hydrolysis.
Heteropolysaccharides (heterogenous) are made of two or more different monosaccharides.

Homogenous Polysaccharides

Pentosans: Yield pentose units on hydrolysis.
- Found mainly in vegetable gums like arabinose.
Hexosans
- Glucosan: Yield only glucose units on hydrolysis.
  - Examples include starch, dextrins, cellulose.
  - Starch and dextrins are storage forms found in tubers and roots.
  - Cellulose is a linear polymer of β-glucose units linked by β-1,4 glycosidic linkages.
  - Cellulose cannot be digested by humans.
- Fructosan: Yield only fructose units on hydrolysis.
  - Example is Inulin.
  - Inulin is a linear polymer of β-D-fructose units linked by β(2,1) linkages.
  - Inulin cannot be digested by humans.
- Dextran
  - Found in cherry gum.
Medical uses:
- Dextran: Used as a blood plasma expander.
- Inulin: Used as a dietary fiber and to measure Glomerular filtration rate (GFR).

Derivatives of Monosaccharides

Sugar Acids:
- Aldonic Acids: Have a COOH group formed by oxidizing the aldehyde group.
  - Examples are gluconic acid and glyceric acid.
  - L-ascorbic acid (vitamin C) is an aldonic acid.
- Uronic Acids: COOH group formed by oxidizing the last -CH2OH group.
  - Examples are glucuronic acid (from glucose) and galacturonic acid (from galactose).
- Aldaric Acids: Have COOH groups formed by oxidizing both the aldehyde group and the last -CH2OH group.
  - Examples are glucaric (or saccharic) acid from glucose and mucic acid from galactose.

Disaccharides

Reducing Disaccharides: Contain a free aldehyde group, forming an osazone.
- Maltose: Composed of two α-glucose units linked by α,1-4 glycosidic linkage.
- Lactose: Composed of glucose and β-galactose linked by β,1-4 glycosidic linkage.
- Cellobiose: Composed of two β-glucose units linked by β,1-4 glycosidic linkage, found in cellulose.
Non-reducing Disaccharides: Do not have a free aldehyde group.
- Sucrose:
  - It results from the careful hydrolysis of cellulose.
  - Not fermented by yeast.
Disaccharides further classified into two types:
- Reducing disaccharides
- non-reducing disaccharides.
- Reducing disaccharides contain free aldehyde groups and forms osazones.
- Non-reducing disaccharides do not contain free aldehyde groups, and not capable of forming osazones.