Carbohydrates: Structure and Function

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Questions and Answers

What type of bond is formed when an aldose undergoes cyclization?

Covalent bond

Hemiacetal bond (correct)

Ether bond

Hemiketal bond

Which of the following compounds can form a hemiketal bond?

Ribose

Glucose

Fructose (correct)

Galactose

In the context of cyclization, what does the term 'intramolecular' refer to?

Reactions occurring within the same molecule (correct)

Reactions that involve free radicals

Reactions that occur in solution

Reactions between two different molecules

Which of the following represents the cyclized form of glucose?

Glucopyranose Signup and view all the answers

What characterizes the cyclization of a ketose compared to an aldose?

Ketoses form hemiketal bonds, while aldoses form hemiacetal bonds. Signup and view all the answers

Which of the following types of carbohydrates does NOT include glucose in its structure?

Fructose Signup and view all the answers

What type of bond is formed during the creation of disaccharides like maltose?

Glycosidic bond Signup and view all the answers

Which carbohydrate is characterized by both α(1 4) and α(1 6) glycosidic bonds?

Starch Signup and view all the answers

What is the primary product of the dehydration process that forms glycosidic bonds?

Water Signup and view all the answers

Which of the following disaccharides is composed of two glucose molecules linked by an α(1 4) bond?

Maltose Signup and view all the answers

Which type of bond is found in cellulose, distinguishing it from starch?

β(1 4) glycosidic bond Signup and view all the answers

Which carbohydrate serves as a storage form of glucose in animals?

Glycogen Signup and view all the answers

What distinguishes fructose from other monosaccharides discussed?

It is a ketone sugar unlike glucose, which is an aldose. Signup and view all the answers

Which sugar is classified as a reducing sugar and consists of two glucose units linked by a β(1-4) glycosidic bond?

Cellobiose Signup and view all the answers

What distinguishes sucrose from maltose in terms of glycosidic linkage?

Sucrose has an α(1-2) linkage. Signup and view all the answers

Which of the following foods are known to contain high amounts of glucose?

Barley and fruit Signup and view all the answers

What is the structural difference in the anomeric carbon of glucose between maltose and cellobiose?

Cellobiose has the OH pointing up at C1. Signup and view all the answers

Which sugar mentioned is a non-reducing sugar?

Sucrose Signup and view all the answers

Which statement is true about cellobiose?

It is formed from two glucose units. Signup and view all the answers

How is the structure of the β(1-4) glycosidic bond in cellobiose described?

It represents a zig-zag formation. Signup and view all the answers

What is the main cleavage product of starch?

Glucose Signup and view all the answers

What type of sugar is cellulose classified as?

Non-reducing sugar Signup and view all the answers

Which type of linkage is primarily found in glycogen?

α(1→4) linkages Signup and view all the answers

What structural feature of cellulose promotes hydrogen bonding?

Flipping of glucose units Signup and view all the answers

Cellulose is a major component of which plant structure?

Cell wall Signup and view all the answers

Glycogen is primarily stored in which type of animal tissue?

Muscle tissue Signup and view all the answers

What is the primary function of glycogen in animals?

Energy storage Signup and view all the answers

What is the primary structural similarity between glycogen and amylopectin?

Both are glucose polymers with branching Signup and view all the answers

In cellulose, every other glucose unit is flipped over due to which type of linkages?

β(1→4) linkages Signup and view all the answers

What type of polysaccharide is primarily used as an energy storage form in animals?

Glycogen Signup and view all the answers

What type of hydrogen bonds are formed in cellulose due to its structure?

Intra-chain and inter-chain hydrogen bonds Signup and view all the answers

Which sugar is the D-isomer when the OH on the bottom chiral center points to the right?

Glucose Signup and view all the answers

What is the primary structural difference between enantiomers?

They are mirror images of each other. Signup and view all the answers

What distinguishes epimers from other stereoisomers?

They differ in configuration about one chiral center. Signup and view all the answers

Which two sugars differ specifically at the C4 position?

D-glucose and D-galactose Signup and view all the answers

What type of ring structure do pentoses and hexoses form?

Pyranoses and furanoses Signup and view all the answers

Which sugar is considered an epimer of D-glucose?

D-mannose Signup and view all the answers

How many carbon atoms are present in a pyran structure?

6 Signup and view all the answers

What is the shape of the furanose structure?

Five-membered ring Signup and view all the answers

How many chiral centers does D-glucose have?

4 Signup and view all the answers

What is the formula for both D-glucose and D-fructose?

C6H12O6 Signup and view all the answers

What is the relationship between stereoisomers and the number of chiral carbons in a monosaccharide?

Stereoisomers equal $2n$, where n is the number of chiral carbons. Signup and view all the answers

Which molecular structure represents the carbonyl group in D-fructose?

A keto group Signup and view all the answers

What is the total number of stereoisomers for D-glucose?

16 Signup and view all the answers

Which of the following best describes a chiral carbon atom?

A carbon connected to four different groups Signup and view all the answers

What is the common characteristic of stereoisomers?

They have the same molecular formula but different structural configurations. Signup and view all the answers

Study Notes

Carbohydrates: Types, Structure, Function, and Metabolism

Carbohydrates have the basic composition (CH₂O)ₙ
They are classified into four types: monosaccharides, disaccharides, oligosaccharides, and polysaccharides
Monosaccharides: Simple sugars with multiple hydroxyl (-OH) groups. They can be aldoses (aldehyde group) or ketoses (ketone group). Examples include glucose, fructose, galactose, and ribose. Their classification is based on the number of carbon atoms (e.g., triose, pentose, hexose)
Disaccharides: Two monosaccharides covalently linked by a glycosidic bond. Examples include sucrose, lactose, and maltose.
Oligosaccharides: A few (3-10) monosaccharides covalently linked by glycosidic bonds.
Polysaccharides: Polymers consisting of chains of more than 10 monosaccharides covalently linked by glycosidic bonds. Examples include starch (amylose and amylopectin), cellulose, and glycogen.

Sugar Nomenclature

The suffix "-ose" designates a carbohydrate
Prefixes like "tri," "tetra," "penta," and "hexa" indicate the number of carbon atoms in the monosaccharide.
Monosaccharides are named as aldoses or ketoses, depending on whether they have an aldehyde or a ketone group, respectively.

Monosaccharides: Aldoses and Ketoses

Aldoses have an aldehyde group, usually at C1
Ketoses have a ketone group, typically at C2

Stereoisomers (Isomers)

Stereoisomers: Monosaccharides with the same chemical formula but different spatial arrangements of atoms.
Chiral carbons are asymmetric carbon atoms attached to four different atoms or groups.
The number of stereoisomers for a monosaccharide is 2ⁿ, where n is the number of chiral carbons.

D and L Isomers

D and L isomers are stereoisomers relating to the asymmetric carbon atom farthest from the aldehyde or ketone group.
Most naturally occurring sugars are D isomers.

Epimers

Epimers are stereoisomers that differ only in the configuration about one chiral centre
Examples include D-mannose and D-galactose, which are epimers of D-glucose.

Cyclic Forms of Sugars

Haworth projections: Used to represent the cyclic forms of monosaccharides.
Fischer projections: Used to represent the open-chain forms of monosaccharides.
Anomers: Cyclized monosaccharides differing only at the anomeric carbon (C1 for aldoses, C2 for ketoses). Occur as alpha (α) and beta (β) forms. Mutarotation is the interconversion between these forms in solution.

Chair Configuration

The chair configuration represents the actual shape of the pyranose ring.

Monosaccharides: Glucose, Fructose

Glucose is an aldohexose; a six-carbon sugar with an aldehyde group
Fructose is a ketohexose; a six-carbon sugar with a ketone group

Disaccharides: Maltose, Sucrose, Lactose, Cellobiose

Maltose: Two glucose molecules linked by an α(1→4) glycosidic bond
Sucrose: Glucose and fructose linked by an α(1→2) glycosidic bond, a nonreducing sugar
Lactose: Galactose and glucose linked by a β(1→4) glycosidic bond, a reducing sugar
Cellobiose: Two glucose units linked by a β(1-4) glycosidic bond

Polysaccharides: Starch, Cellulose, Glycogen

Starch: Plants store glucose as amylose or amylopectin
Amylose: Linear glucose polymer with α(1→4) linkages
Amylopectin: Branched glucose polymer with α(1→4) and α(1→6) linkages
Cellulose: Linear glucose polymer with β(1→4) linkages, major constituent of plant cell walls
Glycogen: Animals store glucose as glycogen; highly branched glucose polymer with α(1→4) and α(1→6) linkages.

Digestion of Carbohydrates

Complex carbohydrates are broken down into simpler sugars via enzymatic hydrolysis.
Enzymes like amylase (saliva and pancreas), sucrase, lactase, and maltase break down disaccharides and polysaccharides into monosaccharides.

Glyco-conjugates

Glycolipids: Carbohydrates and lipids
Glycoproteins: Carbohydrates and proteins

Functions of Carbohydrates in Biological Systems

Energy source/storage
Cellular signaling and adhesion
Structural components (e.g., cellulose, chitin)

Diabetes mellitus
Lactose intolerance
Fructose intolerance
Galactosemia
Glycogen storage disease

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Description

Explore the fascinating world of carbohydrates, including their types, structures, and functions in metabolism. Dive into monosaccharides, disaccharides, oligosaccharides, and polysaccharides, and learn how they play a crucial role in biological processes. This quiz will enhance your understanding of carbohydrate nomenclature and classification.