Carbohydrates and Their Functions
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Questions and Answers

What carbohydrate is formed by the hydrolysis of sucrose?

  • Maltose
  • Fructose and galactose
  • Lactose
  • Two molecules of glucose (correct)

Which of the following statements about oligosaccharides is accurate?

  • They are exclusively involved in energy storage.
  • They contain 2-10 monosaccharide units. (correct)
  • They consist of 1-2 monosaccharide units.
  • They are only linked to proteins.

Lactose intolerance is primarily due to a deficiency in which enzyme?

  • Lactase (correct)
  • Amylase
  • Cellulase
  • Sucrase

What is the main storage form of carbohydrates in plants?

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

Polysaccharides can be classified into which of the following categories?

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

What are glycolipids and glycoproteins primarily composed of?

<p>Carbohydrates linked to lipids or proteins (A)</p> Signup and view all the answers

Which of the following best describes the linkage in sucrose?

<p>Both anomeric carbons are involved (D)</p> Signup and view all the answers

Which symptom is NOT commonly associated with lactose intolerance?

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

What role do oligosaccharides play on the cell surface?

<p>Assisting in cell recognition and adhesion (A)</p> Signup and view all the answers

What distinguishes homopolysaccharides from heteropolysaccharides?

<p>Their composition of monosaccharide types (D)</p> Signup and view all the answers

Which disaccharide is formed from galactose and glucose through a β1,4 galactosidic linkage?

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

What enzyme is responsible for hydrolyzing maltose into D-glucose?

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

Which polysaccharide is predominantly hydrolyzed by amylase during starch digestion?

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

Which linkage is present in the formation of sucrose?

<p>α 1,2 glucosidic linkage (B)</p> Signup and view all the answers

Which of the following disaccharides is classified as a reducing sugar?

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

Which disaccharide is commonly referred to as table sugar?

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

What type of polysaccharide is primarily used for energy storage in plants?

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

What is the main component of cell walls in plants, which is a type of polysaccharide?

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

Which of the following is a characteristic feature of non-reducing disaccharides?

<p>Does not reduce Benedict's reagent (D)</p> Signup and view all the answers

What distinguishes oligosaccharides from disaccharides?

<p>Oligosaccharides contain three to ten monosaccharide units. (A)</p> Signup and view all the answers

What is the primary function of glycogen in the liver?

<p>Maintain blood glucose levels (C)</p> Signup and view all the answers

Which of the following correctly describes cellulose?

<p>Non-hydrolysable by amylase (A)</p> Signup and view all the answers

Which polysaccharide is primarily found in skeletal muscles and the liver?

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

What type of linkages are found in cellulose?

<p>β1,4-glucosidic linkages (A)</p> Signup and view all the answers

What is the main role of glycosaminoglycans (GAGs)?

<p>Formation of the extracellular matrix (B)</p> Signup and view all the answers

Which source primarily provides starch in the diet?

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

How does the presence of cellulose in the diet benefit digestion?

<p>Increases food bulk and stimulates intestinal contractions (D)</p> Signup and view all the answers

Heteropolysaccharides are defined as polysaccharides formed of:

<p>Multiple types of monosaccharide units (A)</p> Signup and view all the answers

What type of carbohydrate is primarily stored for energy in muscles?

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

Which enzyme is responsible for hydrolyzing starch in the digestive system?

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

Which carbohydrate, when hydrolyzed, results in galactose units?

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

What type of polysaccharide is primarily stored in animal tissues?

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

Which of the following is not classified as a homopolysaccharide?

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

Which compound consists of more than 10 sugar units?

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

Which of the following choices represents a reducing disaccharide?

<p>Both A and C (B)</p> Signup and view all the answers

What is the primary structural role of cellulose in plants?

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

Which of the following is characteristic of non-reducing sugars?

<p>They cannot act as reducing agents. (A)</p> Signup and view all the answers

Which carbohydrate serves as a significant energy source in plants?

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

Which statement is true regarding disaccharides?

<p>Disaccharides consist of two sugar units. (C)</p> Signup and view all the answers

Flashcards

Disaccharide

Two monosaccharides linked by a glycosidic bond.

Reducing disaccharide

A type of disaccharide that can act as a reducing agent due to a free anomeric carbon.

Non-reducing disaccharide

A type of disaccharide that cannot act as a reducing agent because the anomeric carbons of both monosaccharides are involved in the glycosidic bond.

Lactose

A disaccharide formed by the union of galactose and glucose via a β1,4 glycosidic linkage.

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Lactase

Lactose is broken down into glucose and galactose by this enzyme.

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Maltose

A disaccharide formed by two glucose molecules linked by an α1,4 glycosidic bond.

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Maltase

Maltose is broken down into two glucose molecules by this enzyme.

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Sucrose

A disaccharide composed of glucose and fructose linked by an α1,2 glycosidic bond.

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Oligosaccharide

Oligosaccharides are short chains of 2-10 monosaccharide units linked by glycosidic bonds.

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Polysaccharide

Polysaccharides are large polymers composed of many monosaccharide units linked together by glycosidic bonds.

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Homopolysaccharide

Polysaccharides made up of only one type of monosaccharide unit, like starch.

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Heteropolysaccharide

Polysaccharides made up of different types of monosaccharides, like hyaluronic acid.

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Starch

A type of homopolysaccharide that serves as the primary energy storage carbohydrate in plants.

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Glycogen

A homopolysaccharide that is the primary energy storage carbohydrate in animals.

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Cellulose

A homopolysaccharide that is a major structural component of plant cell walls.

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Glycosaminoglycans (GAGs)

A class of heteropolysaccharides known for their structural and lubricative properties.

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Lactose intolerance

A condition resulting from the inability to digest lactose, caused by insufficient lactase enzyme.

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What is starch?

Starch is a complex carbohydrate made up of many glucose units linked together. It's the main storage form of carbohydrates in plants.

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How is starch broken down?

The amylase enzyme breaks down starch into simpler sugars, like glucose, during digestion.

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What is glycogen and where is it stored?

Glycogen is the way our bodies store carbohydrates, similar to how plants use starch. It's primarily found in muscles and the liver.

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What is the role of liver glycogen?

Liver glycogen helps maintain a stable blood sugar level. When blood sugar is low, the liver releases glucose from glycogen.

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What is the role of muscle glycogen?

Muscle glycogen serves as a direct energy source for muscle contractions. Muscles use glycogen to fuel their activity.

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What is cellulose?

Cellulose is a long, straight chain of glucose molecules that forms the structural component of plant cell walls. It's what makes plants strong and rigid.

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Why can't our bodies digest cellulose?

Unlike starch, cellulose can't be broken down by the amylase enzyme in our bodies because of the type of bond between its glucose units.

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Why is cellulose important for our health?

Cellulose in our diet helps keep our digestive system healthy. It adds bulk to food, making it easier to move through the intestines and preventing constipation.

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What are heteropolysaccharides?

Heteropolysaccharides are complex carbohydrates made up of different types of sugar molecules. They are important for various functions in the body.

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What are Glycosaminoglycans (GAGs)?

Glycosaminoglycans (GAGs) are a type of heteropolysaccharide found in the extracellular matrix (ECM). They are long chains of sugar molecules that help provide structure and support to tissues.

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What disaccharide yields galactose upon hydrolysis?

Lactose, a disaccharide, breaks down into glucose and galactose upon hydrolysis.

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Which polysaccharide is the animal carbohydrate storage form?

Glycogen is the primary storage form of glucose in animals, acting as an energy reserve.

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Which of the following is NOT a homopolysaccharide?

GAGs (Glycosaminoglycans) are heteropolysaccharides, meaning they are composed of multiple different sugar monomers.

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Name two reducing disaccharides.

Reducing disaccharides have a free anomeric carbon, allowing them to act as reducing agents. Examples include lactose and maltose.

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Name two homopolysaccharides.

Homopolysaccharides are long chains composed of only one type of sugar monomer. Examples include starch, glycogen, and cellulose.

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Study Notes

Course Information

  • Academic Year: 2024-2025
  • Year: 1
  • Semester: 1
  • Module: Human Body Function (HBF) 102

Carbohydrate Chemistry II

  • Lecturer: Dr. Sara Sayed Kadry Abdallah
  • Department: Medical Biochemistry & molecular biology, faculty of medicine, Cairo university

Objectives

  • Define and Classify disaccharides
  • Recognize the significance of different types of disaccharides
  • Define and recognize the significance of oligosaccharides
  • Correlate knowledge to a clinical situation
  • Identify the different types of Polysaccharides
  • Recognize the functional significance of the different types of Polysaccharides
  • List the properties and functions of monosaccharides, disaccharides, and polysaccharides

Introduction - Disaccharides

  • Definition: Two monosaccharide units joined by a glycosidic linkage
  • Classification:
    • Reducing disaccharides (lactose, maltose)
    • Non-reducing disaccharides (sucrose)

Introduction - Lactose

  • Lactose is also called milk sugar
  • Formed from galactose and glucose linked by a β1,4-galactosidic linkage
  • Hydrolyzed by lactase enzyme or by acids into D-glucose and D-galactose

Introduction - Maltose

  • Maltose is called malt sugar
  • Formed from two glucose molecules linked by an α1,4-glucosidic linkage
  • Product of starch digestion by amylase
  • Hydrolyzed by maltase enzyme or by acids into two D-glucose molecules

Introduction - Sucrose

  • Sucrose is also called table sugar
  • Found in sugar cane, beets, and some fruits
  • Formed from glucose and fructose linked by an α1,2-glucosidic linkage
  • Both anomeric carbons are involved in the linkage, thus it is non-reducing
  • Hydrolyzed by sucrase enzyme into 2 molecules of glucose

Introduction - Oligosaccharides

  • Definition: Carbohydrates containing two or more monosaccharides (2-10 units)
  • Significance: Linked to lipids or proteins (forming glycolipids and glycoproteins) on cell surfaces; involved in cell recognition and adhesion

Introduction - Clinical Correlation - Lactose Intolerance

  • Lactose intolerance occurs when the small intestine does not produce enough lactase (an enzyme that digests lactose)
  • Symptoms: abdominal pain, diarrhea, and flatulence
  • Infants with lactose intolerance require lactose-free milk

Introduction - Polysaccharides

  • Definition: Carbohydrates composed of more than 10 monosaccharide units linked by glycosidic bonds
  • Classification:
    • Homopolysaccharides (starch, glycogen, cellulose)
    • Heteropolysaccharides (GAGs)

Introduction - Homopolysaccharides - Starch

  • Starch is a homopolysaccharide composed of glucose units linked by glycosidic bonds
  • Chief storage form of carbohydrates in plants
  • Found in cereals, tubers (potatoes, sweet potatoes), and legumes
  • Hydrolyzed by amylase in the digestive system

Introduction - Homopolysaccharides - Glycogen

  • Glycogen is the storage form of carbohydrates in animals
  • Found primarily in skeletal muscle and liver
  • Liver glycogen maintains blood glucose levels
  • Muscle glycogen provides energy for contracting muscle

Introduction - Homopolysaccharides - Cellulose

  • Cellulose forms the principal part of plant cell walls
  • Long, non-branched chain of β-glucose units linked by β1,4-glucosidic linkages
  • Not digestible by human amylase
  • Provides bulk in the diet, stimulating intestinal contractions and preventing constipation

Introduction - Heteropolysaccharides- Glycosaminoglycans (GAGs)

  • Polysaccharides formed from more than one type of monosaccharide
  • GAGs are long, unbranched chains of repeating disaccharide units, typically containing an amino sugar and a uronic acid
  • Located in the extracellular matrix (ECM) and associated with other extracellular proteins

Interactive Questions

  • (Question 1): The correct answer is Lactose
  • (Question 2): The correct answer is Glycogen
  • (Question 3): The correct answer is GAGs

Summary

  • Carbohydrates are classified into monosaccharides, disaccharides, and polysaccharides
  • Disaccharides are formed from two sugar units
  • Disaccharides are classified as reducing or non-reducing
  • Polysaccharides are formed from more than 10 sugar units
  • Important homopolysaccharides are starch, glycogen, and cellulose

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Description

Test your knowledge on carbohydrates with this quiz covering their hydrolysis, storage, and functional roles in biology. Explore questions about oligosaccharides, polysaccharides, and lactose intolerance, among other topics. Ideal for students studying biochemistry or nutrition.

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