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Questions and Answers

What is the chemical formula for D-Glucose?

  • C6H10O5
  • C5H10O5
  • C7H14O7
  • C6H12O6 (correct)

Which of the following statements is true regarding hexoses?

  • They always exist as aldohexoses.
  • They contain 5 carbon atoms.
  • They have the molecular formula C6H12O6. (correct)
  • They consist of 4 hydrogen atoms.

Which monosaccharide is known as blood sugar in the body?

  • D-Glucose (correct)
  • Galactose
  • Mannose
  • D-Fructose

What is the main dietary source of Galactose?

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

What is the significance of D-Fructose in nutrition?

<p>It is the sweetest carbohydrate. (A)</p> Signup and view all the answers

What condition is caused by the inability to convert galactose to glucose?

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

How are disaccharides structurally formed?

<p>From two monosaccharides bonded together. (A)</p> Signup and view all the answers

Which of the following is NOT a nutritional hexose?

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

What is the primary function of carbohydrates in the body?

<p>Supply energy needs (A)</p> Signup and view all the answers

How are carbohydrates classified based on the number of sugar units?

<p>Monosaccharides, disaccharides, oligosaccharides, and polysaccharides (D)</p> Signup and view all the answers

Which type of carbohydrate cannot be hydrolyzed into simpler forms?

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

Which of the following is an example of a pentose monosaccharide?

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

What type of bond links monosaccharides together in disaccharides?

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

Which statement about aldoses and ketoses is correct?

<p>Aldoses contain an aldehyde group, while ketoses contain a ketone group. (B)</p> Signup and view all the answers

What type of bond links the monosaccharides in disaccharides?

<p>O-glycosidic bond (B)</p> Signup and view all the answers

Which of the following disaccharides is exclusively found in the milk of mammals?

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

What is the general formula for carbohydrates in terms of carbon, hydrogen, and oxygen?

<p>C_nH_{2n}O_n (A)</p> Signup and view all the answers

Which enzyme specifically cleaves sucrose into glucose and fructose?

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

Which monosaccharide is an example of a triose?

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

Which statement regarding maltose is true?

<p>It is a disaccharide also known as malt sugar. (C)</p> Signup and view all the answers

How is lactose hydrolyzed in humans?

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

Which of the following correctly describes oligosaccharides?

<p>They are composed of 3 to 10 sugar units. (A)</p> Signup and view all the answers

What percentage of total carbohydrates does lactose contribute to a typical diet?

<p>10% (A)</p> Signup and view all the answers

Which of the following statements about ribose and deoxyribose is correct?

<p>Both are structural elements of nucleic acids. (A)</p> Signup and view all the answers

Flashcards

Carbohydrate

A large group of organic compounds composed of carbon, hydrogen, and oxygen. They are the primary source of energy for the body and often have a hydrogen to oxygen ratio of 1:2:1

Monosaccharide

A simple sugar that cannot be broken down into smaller sugar molecules. They serve as the building blocks for larger carbohydrates.

Disaccharide

A sugar molecule made up of two monosaccharides linked together by a glycosidic bond.

Polysaccharide

A complex carbohydrate made up of many monosaccharide units linked together by glycosidic bonds.

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Glycosidic Linkage

The chemical bond that connects two monosaccharides together in a disaccharide or polysaccharide.

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Aldose

A monosaccharide with an aldehyde functional group at the end of its carbon chain.

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Ketose

A monosaccharide with a ketone functional group within its carbon chain.

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D and L Isomers

Two enantiomers of monosaccharides that differ in their spatial arrangement around a chiral carbon. D-isomers are found in nature.

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D-Glucose

An aldohexose found in fruits, corn syrup, and honey. It's the primary blood sugar and a building block for larger carbohydrates.

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D-Fructose

A ketohexose, the sweetest carbohydrate, found in fruits and honey. It's part of sucrose.

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Galactose

Not found alone, mostly in lactose (milk sugar). It's crucial for infant development.

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Why are disaccharides called 'di'saccharides?

Because they are composed of two monosaccharide units.

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What is the main dietary carbohydrate for infants?

Lactose, often referred to as 'milk sugar,' is the primary carbohydrate source for infants.

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Lactose intolerance

A condition where the body has difficulty digesting lactose due to a deficiency of the lactase enzyme.

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Sucrose

A disaccharide consisting of glucose and fructose, commonly found in table sugar.

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What is the common enzyme that breaks down sucrose?

Sucrase, also known as invertase, breaks down sucrose into glucose and fructose.

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Oligosaccharide

A carbohydrate composed of 3 to 10 linked monosaccharides.

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Ribose and Deoxyribose

These are pentose sugars that are crucial components of nucleic acids like DNA and RNA.

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Study Notes

Carbohydrates: Chemistry Overview

  • Carbohydrates (CHO) are the primary energy source in the diet, comprising 48% of caloric needs.
  • The hydrogen to oxygen ratio in most CHOs is 1:2:1.
  • CHOs are a group of organic compounds.

Carbohydrate Functions

  • Supply energy for bodily functions, Glucose is the primary fuel for cells.
  • Serve as energy storage (e.g., starch, glycogen).
  • Component of glycolipids and glycoproteins, crucial for membrane structure and functions like cell growth, adhesion, and fertilization.
  • Involved in the synthesis of fatty acids and amino acids, as well as the complete oxidation of fats.
  • Ribose sugar is a component of RNA.

Carbohydrate Classification

  • Classified based on the number of sugar units.
  • Monosaccharides: Single sugar units, not hydrolyzable into simpler carbohydrates.
    • Triose: 3 carbon atoms (e.g., glyceraldehyde, dihydroxyacetone).
    • Pentose: 5 carbon atoms (e.g., ribose, ribulose).
    • Hexose: 6 carbon atoms (e.g., glucose, fructose).
  • Disaccharides: Two monosaccharides linked together. Bonds are called glycosidic linkages.
  • Oligosaccharides: 3 to 10 monosaccharides linked together.
  • Polysaccharides: Polymers of monosaccharides.

Monosaccharides: Aldoses and Ketoses

  • Aldoses: Contain an aldehyde group.
  • Ketoses: Contain a ketone group.

Hexoses

  • Contain 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms (C6H12O6).
  • Can exist in either aldo or keto forms.
  • Nutritionally important hexoses include glucose, galactose, mannose, and fructose.

Examples of Common Monosaccharides

  • Glucose: Found in fruits, corn syrup, and honey; also known as blood sugar (70-120 mg/dL in the blood); a major component of di- and polysaccharides
  • Fructose: The sweetest carbohydrate; found in fruit juices and honey; a component of sucrose.
  • Galactose: Not a naturally occurring monosaccharide; part of lactose (milk sugar).

Examples of Disaccharides

  • Maltose: Composed of two glucose molecules; formed during starch digestion.
  • Lactose: Composed of glucose and galactose; the primary sugar in milk.
  • Sucrose: Composed of glucose and fructose; commonly obtained from sugarcane and sugar beets.

Important Note on Galactosemia

  • Infants with galactosemia lack the enzyme to convert galactose to glucose, resulting in toxicity, mental retardation, and liver damage. Treatment involves removing milk and lactose from the diet.

Oligosaccharides—Important Pentoses

  • Ribose and deoxyribose are structural components of nucleic acids and coenzymes (e.g., ATP, NAD).

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