Carbohydrates and Their Types
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Questions and Answers

What is the result of oxidation of aldoses with Tollen's reagent?

  • Formation of alditols
  • Production of a silver mirror indicating the presence of an aldehyde group (correct)
  • Formation of sugar phosphates
  • Conversion into lactones

Which reaction involves the interconversion of α and β anomers?

  • Glycoside formation
  • Oxidation to sugar acids
  • Mutarotation (correct)
  • Osazone formation

What classifies sugar as reducing sugars?

  • Non-reducing for ketoses
  • Ability to oxidize with HNO3
  • Presence of an aldehyde group (correct)
  • Formation of lactones

What occurs during the exhaustive methylation of carbohydrate compounds?

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

Which statement about the formation of sugar acids is true?

<p>Sugar acids provide energy for organisms (D)</p> Signup and view all the answers

Which of the following is NOT formed from the oxidation of aldoses?

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

What defines a reducing sugar among monosaccharides?

<p>Presence of an aldehyde or a free ketone group (B)</p> Signup and view all the answers

What type of linkage is found in sucrose, the common table sugar?

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

What is the outcome of glycoside formation?

<p>Creation of acetal from an aldose (B)</p> Signup and view all the answers

What is the full name representation of lactose?

<p>β-D-galactopyranosyl-(1→4)-α-D-glucose (A)</p> Signup and view all the answers

What is the main function of carbohydrates in biological systems?

<p>To provide energy and act as metabolic intermediates (A)</p> Signup and view all the answers

Which of the following correctly describes monosaccharides?

<p>They are simple sugars with the general formula Cn(Hâ‚‚O)n (B)</p> Signup and view all the answers

Which of the following correctly describes the structure of maltose?

<p>α(1→4) glycosidic bond (D)</p> Signup and view all the answers

What structural difference exists between aldoses and ketoses?

<p>Aldoses have an aldehyde group at one end, while ketoses have a keto group usually at C2 (A)</p> Signup and view all the answers

What occurs when HCl gas is introduced to a solution of D-(+)-glucose in methanol?

<p>Formation of sugar sulfates (A)</p> Signup and view all the answers

What characterizes sulfate groups in sugar molecules?

<p>They render sugars negatively charged at physiological pH (A)</p> Signup and view all the answers

What do D and L configurations in sugars refer to?

<p>The configuration of the asymmetric C farthest from the aldehyde or keto group (B)</p> Signup and view all the answers

Which of the following is an example of homopolysaccharide?

<p>All of the above (D)</p> Signup and view all the answers

What kind of cyclic forms can fructose form during the cyclization of sugars?

<p>Both 6-member pyranose and 5-member furanose rings (C)</p> Signup and view all the answers

What type of polysaccharide consists of two or more different types of monosaccharides?

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

In the classification of carbohydrates, which of the following represents complex carbohydrates?

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

What type of carbohydrate is glucose considered to be?

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

Which term describes the acetal form of glucose?

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

Epimerism in carbohydrates occurs when:

<p>Two sugars differ only at one asymmetric carbon (D)</p> Signup and view all the answers

What type of ring structure does glucose form upon cyclization?

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

Which description accurately differentiates between the alpha and beta anomers of glucose?

<p>Alpha has OH group below the ring, beta has it above. (A)</p> Signup and view all the answers

Which of the following describes the mechanism of pyranose formation?

<p>The reaction involves the aldehyde at C1 and a distal OH. (B)</p> Signup and view all the answers

What is a unique characteristic of sugar alcohols?

<p>They lack an aldehyde or ketone. (D)</p> Signup and view all the answers

What change occurs in sugar acids compared to regular sugars?

<p>They are oxidized to a carboxylic acid. (A)</p> Signup and view all the answers

What is a defining feature of amino sugars?

<p>An amino group substitutes for a hydroxyl group. (C)</p> Signup and view all the answers

What role does sialic acid play in glycoproteins?

<p>It imparts a negative charge due to its carboxyl group. (A)</p> Signup and view all the answers

Which configuration do pyranose sugars commonly assume?

<p>Chair or boat configuration (C)</p> Signup and view all the answers

What is the primary component of bacterial cell walls that provides mechanical support?

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

What characterizes glycosaminoglycans (GAGs)?

<p>They have disaccharide repeating units. (D)</p> Signup and view all the answers

Which of the following is a major component of proteoglycans?

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

Which type of sugar is typically linked to glycoproteins at the asparagine side chain?

<p>N-acetylglucosamine (B)</p> Signup and view all the answers

What inhibits the cross-linking of peptidoglycan in bacterial cell walls?

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

What percentage of carbohydrates by weight can be found in proteoglycans?

<p>Up to 95% (D)</p> Signup and view all the answers

Which of the following groups is characteristic of glycosaminoglycans?

<p>Negatively charged carboxylate or sulfate groups (C)</p> Signup and view all the answers

How are glycoproteins differentiated from other glycoproteins?

<p>By the arrangement of their sugar side chains (A)</p> Signup and view all the answers

What is the primary role of glycosaminoglycans (GAGs) within the extracellular matrix?

<p>To regulate the movement of molecules and cells (C)</p> Signup and view all the answers

Which of the following best describes the structure of aggrecan?

<p>A polymeric complex with multiple GAG chains (D)</p> Signup and view all the answers

What happens when a foreign antigen is introduced to a person who does not naturally have it?

<p>The immune system recognizes it as foreign and responds (B)</p> Signup and view all the answers

Which statement accurately describes the function of proteoglycans in the extracellular matrix?

<p>They associate with fibrous proteins to maintain matrix integrity (C)</p> Signup and view all the answers

What factor influences the selective sieving ability of GAG gels?

<p>The pore sizes and charge densities of the gels (B)</p> Signup and view all the answers

Flashcards

Carbohydrates

Organic compounds containing carbon, hydrogen, and oxygen, with a general formula Cn(H2O)n, often serving as energy sources or structural components.

Monosaccharides

Simple sugars, the fundamental building blocks of carbohydrates.

Aldoses

Monosaccharides containing an aldehyde group at one end.

Ketoses

Monosaccharides containing a ketone group, usually at carbon 2.

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Stereoisomerism (D vs L)

Different spatial arrangements of atoms arranged in mirror image form in sugars. D and L designations are based on the configuration around the chiral carbon.

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Epimers

Sugars differing in configuration at only one asymmetric carbon atom.

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Cyclization of Sugars

Formation of ring structures (pyranose or furanose) from linear monosaccharides through intramolecular reactions.

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Hemiacetal/Hemiketal Formation

Reactions forming ring structures by connecting an aldehyde or ketone group with a hydroxyl group on another carbon.

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Haworth Projection

A two-dimensional representation of cyclic sugars, depicting the ring structure as almost flat.

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Pyranose Ring

A six-membered ring formed by the intramolecular reaction of an aldehyde or ketone group with a hydroxyl group on another carbon.

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Chair and Boat Conformations

Pyranose sugars can exist in two major conformations due to the tetrahedral nature of carbon bonds: chair and boat.

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Sugar Alcohol

A sugar derivative where the carbonyl group (aldehyde or ketone) is reduced to a hydroxyl group.

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Sugar Acid

A sugar derivative formed by oxidizing the aldehyde group at C1 or the hydroxyl group at C6 to a carboxylic acid.

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Deoxy Sugar

A sugar derivative where a hydroxyl group is replaced by a hydrogen atom.

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Sialic Acid

A negatively charged sugar derivative, often found as a terminal residue in oligosaccharide chains of glycoproteins.

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What are disaccharides?

Disaccharides are carbohydrates composed of two monosaccharides linked by a glycosidic bond.

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What is a glycosidic bond?

A glycosidic bond is a covalent bond formed between the anomeric carbon of a sugar and a hydroxyl group of another molecule, like another sugar.

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Sucrose

Sucrose is a disaccharide composed of glucose and fructose linked by an α(1→2) glycosidic bond.

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Lactose

Lactose is a disaccharide composed of galactose and glucose linked by a β(1→4) glycosidic bond.

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Homopoly vs Heteropoly

Homopoly: Polysaccharides composed of only one type of monosaccharide. Heteropoly: Polysaccharides composed of more than one type of monosaccharide.

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Why are polysaccharides important?

Polysaccharides play vital roles in energy storage and maintaining structural integrity in organisms.

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Mutarotation

The interconversion of α and β anomers of a sugar in an aqueous solution. This happens because the open-chain form of the sugar is in equilibrium with the cyclic forms, allowing the anomeric carbon to change configuration.

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Oxidation to Sugar Acids

Sugars can be oxidized (gain oxygen) to form different types of acids. Oxidation happens at the carbonyl (CHO) group or hydroxyl (OH) groups of sugars.

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Aldonic Acid

A sugar acid formed when the carbonyl (CHO) group of an aldose is oxidized to a carboxyl (COOH) group.

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Uronic Acid

A sugar acid formed when a hydroxyl (OH) group on the sixth carbon (C6) of a hexose is oxidized to a carboxyl (COOH) group.

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Aldaric Acid

A sugar acid formed when both the carbonyl group (CHO) and the hydroxyl group (OH) on the sixth carbon (C6) of an aldose are oxidized to carboxyl groups (COOH).

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Reducing Sugar

A sugar that can reduce other compounds (like Tollen's reagent) because it has a free carbonyl group (CHO) that can be oxidized.

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Osazone Formation

A reaction of an aldose with phenylhydrazine that produces an osazone. This reaction forms a characteristic crystalline derivative that can be used to identify the sugar.

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Peptidoglycan

A unique polymer that forms bacterial cell walls, preventing them from bursting due to internal osmotic pressure. It's made up of linear polysaccharide chains cross-linked by short peptides.

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Penicillin's Action

Penicillin inhibits the cross-linking enzyme (transpeptidase) in peptidoglycan synthesis, preventing the formation of a strong bacterial cell wall, ultimately killing bacteria.

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What are Glycosaminoglycans?

Repeating disaccharide units, made up of an amino sugar (glucosamine or galactosamine) and a negatively charged carboxylate or sulfate group, often attached to proteins to form proteoglycans, found in animal cells.

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Proteoglycans

Large molecules that are essentially 'protein cores' with covalently attached glycosaminoglycans (GAGs). These are found in animal cells and contribute to structural support and cell signaling.

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Glycoproteins

Proteins with covalently linked oligosaccharide chains. These sugars are attached to either the amino group of asparagine (N-linkage) or the hydroxyl group of serine/threonine (O-linkage).

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Difference between Glycoproteins and Proteoglycans

Glycoproteins have a smaller percentage of carbohydrate compared to proteoglycans. They are differentiated by the nature, quantity, and arrangement of their sugar side chains.

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Linkage in Proteoglycans

The GAG chain in a proteoglycan is linked to its protein core through a specific carbohydrate linkage. This unique connection is crucial for the structure and function of proteoglycans.

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Proteoglycan Functions

Proteoglycans are large, complex molecules that form gels in the extracellular matrix (ECM). These gels act as filters, controlling the movement of molecules and cells based on size and charge. They also bind to fibrous proteins, like collagen, to maintain ECM structure.

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What are GAGs?

GAGs are long, unbranched polysaccharide chains that are negatively charged. They are a key component of proteoglycans and form the gel-like structure in the ECM.

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Aggrecan

A major proteoglycan found in cartilage, it has a large molecular weight (millions of Daltons) and can bind over 100 GAG chains.

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Decorin

A smaller proteoglycan secreted by fibroblasts, it has only one GAG chain and interacts with collagen fibers.

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Blood Group Antigens

Carbohydrates on the surface of red blood cells act as antigens, determining blood group types (e.g., A, B, O). These antigens trigger an immune response if a person receives blood from a different blood group.

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Study Notes

Carbohydrates

  • Carbohydrates are compounds containing carbon, hydrogen, and oxygen. They have the general formula Cn(H2O)n.
  • They are major components of life, making up most organic matter.
  • Functions include energy storage, metabolic intermediates, and structural framework of RNA and DNA (in certain organisms).
  • Classified into simple and complex carbohydrates.

Monosaccharides

  • Simplest carbohydrates
  • Have aldehyde or ketone groups with multiple hydroxyl groups.
  • Examples include glucose, fructose, and galactose.
  • Classified into aldoses (aldehyde group) and ketoses (ketone group).
  • Stereoisomers (D and L forms): D & L designation depends on the chirality around the carbon furthest from the aldehyde or ketone.
  • Epimers are stereoisomers that differ at only one chiral carbon.
  • Nomenclature based on number of carbons (triose, tetrose, pentose, hexose) and the presence of aldehyde or ketone group.

Disaccharides and Polysaccharides

  • Disaccharides are formed by combining two monosaccharides via a glycosidic bond.
  • Examples include sucrose (glucose + fructose), lactose (galactose + glucose), and maltose (glucose + glucose).
  • Polysaccharides are formed by linking many monosaccharides through glycosidic bonds.
  • Examples include starch (amylose and amylopectin), glycogen, and cellulose.

Cyclization of Sugars

  • Monosaccharides can cyclize to form ring structures (hemiacetals or hemiketals).
  • This is crucial for their stability and function.
  • Anomers are different ring forms distinguished by the position of the hydroxyl group on the anomeric carbon.

Sugar Derivatives

  • Sugar alcohols lack an aldehyde or ketone and are formed by reduction reactions.
  • Sugar acids are formed by oxidation reactions.
  • Deoxysugars are formed by removal of one or more hydroxyl groups.
  • Amino sugars are characterized by the presence of an amino group.

Reactions of Monosaccharides

  • Mutarotation involves the interconversion of α and β anomers in solution.
  • Oxidation reactions produce sugar acids.
  • Reduction reactions form sugar alcohols.
  • Osazone formation is a characteristic reaction for glucose.

Disaccharides

  • Disaccharides are formed by linking two monosaccharides through glycosidic bonds.
  • Examples include sucrose, lactose, and maltose.
  • Glycosidic bonds connect the anomeric carbon of one monosaccharide to another.

Polysaccharides

  • Polysaccharides are long chains of monosaccharides linked by glycosidic bonds.
  • Examples include starch, glycogen, and cellulose.
  • Starch and glycogen are storage forms of glucose; cellulose provides structural support.

Others

  • Glycoproteins and proteoglycans are proteins with attached carbohydrates.
  • Structural and functional roles in cells and organisms.
  • Include peptidoglycan, a component of bacterial cell walls, and glycosaminoglycans (GAGs), components of ECM and proteoglycans, playing a crucial role in structural integrity and cell signaling.
  • Blood group antigens are oligosaccharides found on cell surfaces, determining blood type and playing a role in immune responses.

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Description

This quiz covers the fundamentals of carbohydrates, including their structure, function, and classification into monosaccharides, disaccharides, and polysaccharides. You'll also learn about specific examples and the importance of carbohydrates in biological systems.

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