Carbohydrates and Simple Sugars

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Questions and Answers

What are the two sugars that compose sucrose?

Glucose and galactose

Lactose and glucose

Glucose and fructose (correct)

Fructose and maltose

Which glycosidic bond is found in lactose?

β-1,4 glycosidic bond (correct)

γ-1,6 glycosidic bond

α-1,4 glycosidic bond

α-1,2 glycosidic bond

Where are O-linked sugars added in the cell?

Golgi apparatus (correct)

Cytoplasm

Nucleus

Endoplasmic reticulum

What is the typical range of sugar residues in oligosaccharides?

3 to 9 residues Signup and view all the answers

Which of the following polysaccharides is known for its structural role in plants?

Cellulose Signup and view all the answers

Which statement about N-linked sugars is correct?

They are attached starting in the endoplasmic reticulum. Signup and view all the answers

How many glucose molecules are linked in maltose?

Two Signup and view all the answers

What is the primary function of oligosaccharides in cells?

Cellular identity Signup and view all the answers

Which polysaccharide is characterized by α-1,4 glycosidic links and is a component of starch?

Amylose Signup and view all the answers

What is the primary structural component of cellulose?

Unbranched homopolysaccharide Signup and view all the answers

Which of the following describes the branching structure of glycogen compared to amylopectin?

Branches after every 8-12 residues Signup and view all the answers

Which statement best describes proteoglycans?

They are formed by polysaccharide compounds linked to proteins with extensive chemical modification of sugars. Signup and view all the answers

Which of these sugar types is NOT a monomer found in hemicellulose?

Glucose Signup and view all the answers

What type of sugar is D-Fructose classified as?

Ketose Signup and view all the answers

What is the primary difference between D-Glucose and L-Glucose?

The configuration at one or more asymmetric carbons Signup and view all the answers

Which of the following describes diastereomers?

Isomers that have the same chemical type and size, but are non-mirror images Signup and view all the answers

What new asymmetric center formed during sugar cyclization is known as?

Anomeric carbon Signup and view all the answers

Which of the following sugars is classified as an aldohexose?

D-Galactose Signup and view all the answers

Which statement correctly defines a reducing sugar?

A sugar that has an open-chain form with an aldehyde group Signup and view all the answers

What is the primary characteristic of epimers?

They are non-mirror image diastereomers differing at one specific carbon Signup and view all the answers

Which sugar is a trioses type?

D-Glyceraldehyde Signup and view all the answers

Which of the following statements is true regarding ketoses?

Some ketoses can tautomerize to form an aldehyde group in solution Signup and view all the answers

Which configuration describes the arrangement of the hydroxyl groups in D-Glucose?

D-configuration Signup and view all the answers

Study Notes

Carbohydrates

Carbohydrates are compounds with the general formula Cx(H₂O)x.
They are also called saccharides.
Monosaccharides are simple sugars, including glucose, fructose, ribose, galactose, and glyceraldehyde.
Glucose and fructose have the formula C₆H₁₂O₆.
Ribose has the formula C₅H₁₀O₅.
Glyceraldehyde has the formula C₃H₆O₃.
Aldehydes are aldoses; ketones are ketoses.
Monosaccharides are classified by the number of carbons (triose, tetrose, pentose, hexose, heptose, and so on).
Common sugars include glucose, fructose, galactose, and their derivatives.
Different sizes of monosaccharides are detailed in image representations.

Common Sugars

Glucose is an aldose.
Fructose is a ketose.
Glucose and fructose are both hexoses (6 carbons).
Glucose chemical structure is shown.
Fructose chemical structure is shown.

Simple Sugars

Different types of simple sugars are detailed in image representations.
Simple sugars, including D-ribose, D-glucose, D-fructose, D-galactose, and D-mannose, are shown.

Carbonyl on the End - D-Aldoses

D-Glyceraldehyde is a 3-carbon aldose.
D-Erythrose and D-Threose are 4-carbon aldoses, with images to illustrate their structure.

D-Aldoses

D-Ribose, D-Arabinose, D-Xylose, and D-Lyxose are 5 carbon aldoses (pentoses), with image representations.
D-Allose, D-Altrose, D-Glucose, D-Mannose, D-Gulose, D-Idose, D-Galactose, and D-Talose are 6-carbon aldoses (hexoses), with image representations.

Carbonyl Inner-Carbon D-Ketoses

Dihydroxyacetone is a 3-carbon ketose.
D-Erythrulose is a 4-carbon ketose.

D-Ketoses

D-Ribulose, D-Psicose, D-Fructose, D-Xylulose, D-Sorbose, and D-Tagatose (with image representations of their structures).

Asymmetric Carbons

Glyceraldehydes have asymmetric carbons. The carbons with multiple different groups attached are asymmetric.
L-Glyceraldehyde and D-Glyceraldehyde are mirror images.

Multiple Asymmetric Centers

Glucose has multiple asymmetric carbons.
D-Glucose is one configuration around the asymmetric carbon.

Enantiomers

Enantiomers are mirror images of each other.
D-Glucose and L-Glucose are enantiomers.

Diastereomers

Diastereomers have the same chemical type and size, but are not mirror images.
D-Glucose and D-Gulose are diastereomers.

Epimers

Epimers are diastereomers that differ in configuration at only one carbon.
D-Glucose and D-Galactose are epimers.

Cyclization of Sugars

Cyclization of sugars creates a hemiacetal or hemiketal.
New asymmetric carbon is formed- the anomeric carbon.
α-D-Fructofuranose and α-D-Fructopyranose are image examples of cyclic forms of fructose.
Illustrated are examples of α- and β-furanose and pyranose forms of glucose and fructose.

Common Furanoses

Fructose and Ribose are examples of common furanoses. β-D-Fructofuranose and β-D-Ribofuranose image representations.

Oxidation of Sugars-Reducing Sugars

All monosaccharides and some disaccharides (lactose, maltose) are reducing sugars.
A reducing sugar has an open-chain form with an aldehyde or can tautomerize in solution forming an aldehyde.

Basis of Fehling's Reaction - Glucose is Reducing

Glucose, in its open-chain form, is a reducing sugar. A reaction with a copper (II) reagent (Cu²⁺) to a copper(I) (Cu⁺) precipitate.

Glucose Family, Amino Sugars, Deoxy Sugars, Acidic Sugars

Detailed presentation of structural formulas.
Various sugars, their structures, and different modified forms represented visually.

Disaccharides

Sucrose (glucose + fructose), Lactose (glucose + galactose), and Maltose (glucose + glucose) are examples of disaccharides.

Formation of Glycosidic Bonds-Polysaccharides

Polysaccharides are formed by glycosidic bonds.
α-1,4 glycosidic links and Maltose formation are image representations.

Disaccharides-Lactose and Maltose

Lactose (galactose + glucose) and Maltose (glucose + glucose) are examples of disaccharides.
The glycosidic bonds, are shown as image representations.

Oligosaccharides

Oligosaccharides play roles in cellular identity.
Typically composed of 3-9 monosaccharide units and are often attached to biopolymers (proteins, lipids).

Oligosaccharides attached to Proteins

O-linked sugars are added in the Golgi apparatus.
N-linked sugars synthesis starts in the endoplasmic reticulum and is completed in the Golgi apparatus.

Polysaccharides (glycans)

Cellulose, glycogen, amylose, amylopectin, and chitin are types of polysaccharides.
Polysaccharides have various functions including energy storage, structural strength, and lubrication.
Structural formulas for polysaccharide molecules are displayed.

Homopolysaccharides and Heteropolysaccharides

Homopolysaccharides have one type of monomer (e.g., amylose).
Heteropolysaccharides have more than one type of monomer (e.g., hemicellulose).
These categories are illustrated with image representations.

Polysaccharides-Sugar Polymers

Amylose, a component of starch, is an unbranched homopolysaccharide. Structural formulas are displayed.
Cellulose is an unbranched homopolysaccharide. Structural formulas are displayed.

Structure of Amylopectin and Glycogen

Amylopectin and glycogen are branched homopolysaccharides.
Branch points are explained with diagrams.
Glycogen has branch points every 8-12 residues; amylopectin branches every 30–50 residues are explained by diagrams.

Hemicellulose, Chitin

Hemicellulose is a branched heteropolysaccharide. Its monomers are shown.
Chitin is structurally similar to cellulose but with an acetylamine group.

Glycosaminoglycans (mucopolysaccharides)

Examples include keratan sulfate, heparin, hyaluronic acid, and chondroitin sulfate.
These are repeating disaccharide units with negatively charged residues.

Proteoglycans

Proteoglycans are polysaccharides linked to proteins. They have larger sugar components.

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Description

Explore the world of carbohydrates in this quiz, focusing on their structures and types. Learn about monosaccharides, including glucose and fructose, and their classifications such as aldoses and ketoses. Test your knowledge of the different types and formulas of simple sugars.