Carbohydrate Chemistry Overview
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Questions and Answers

What type of dextrin is categorized as straight unbranched and gives a blue color with iodine?

  • Achrodextrin
  • Amylo-dextrin (correct)
  • Erythrodextrin
  • Amylopectin
  • Which of the following is true about cellulose?

  • Its presence is important for stool bulk. (correct)
  • It is formed by α-1,4 glycosidic bonds.
  • It is digestible by humans.
  • It is a source of energy for humans.
  • What is a characteristic of agar in microbiology?

  • It is formed mainly from glucose.
  • It sets to a gel after cooling. (correct)
  • It is soluble in cold water.
  • It is digested by humans.
  • Which type of dextrin is colorless and similar to amylo-dextrin but smaller?

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

    What is the main function of inulin in the body?

    <p>To diagnose kidney function. (C)</p> Signup and view all the answers

    What kind of bonds link the repeated units of fructose in inulin?

    <p>β-1,2 glycosidic bonds (D)</p> Signup and view all the answers

    Which factor differentiates limit dextrin from other dextrins?

    <p>It remains after complete action of β-amylase on starch. (C)</p> Signup and view all the answers

    What similarity does dextrins have with starch?

    <p>Both form sticky, gummy masses when precipitated. (D)</p> Signup and view all the answers

    What distinguishes aldoses from ketoses?

    <p>The presence of a ketone or aldehyde group. (B)</p> Signup and view all the answers

    Which of the following substances are categorized as aldotrioses?

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

    What is the significance of erythrose in biological processes?

    <p>It serves as an intermediate in glucose oxidation. (B)</p> Signup and view all the answers

    What defines a pentose in terms of its carbon atom composition?

    <p>Contains 5 carbon atoms. (D)</p> Signup and view all the answers

    Which of the following is a characteristic of ribose?

    <p>It is a component of ATP and GTP. (A)</p> Signup and view all the answers

    Which of the following correctly identifies a ketohexose?

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

    What condition occurs when large amounts of arabinose are ingested?

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

    Which of the following statements about hexoses is true?

    <p>Glucose is the chief carbohydrate in mammals. (C)</p> Signup and view all the answers

    Which amino sugar is a component of chondroitin sulphate?

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

    What is the structure of muramic acid primarily composed of?

    <p>N-acetylglucosamine linked to a lactic acid residue (C)</p> Signup and view all the answers

    What is the significance of invert sugar in honey?

    <p>It consists of equimolar amounts of glucose and fructose. (C)</p> Signup and view all the answers

    How do amino sugars contribute to the function of certain antibiotics?

    <p>They are believed to be related to the antibiotic activity. (A)</p> Signup and view all the answers

    Which glycoside is known to contain an aglycone that is a steroid?

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

    What is the primary role of sucrase (invertase) in relation to sugars?

    <p>To hydrolyze sucrose into invert sugar. (A)</p> Signup and view all the answers

    What is the consequence of introducing sucrose parenterally?

    <p>It alters the osmotic condition of the blood. (D)</p> Signup and view all the answers

    Which amino sugar is specifically related to neuraminic acid?

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

    What is primarily responsible for the occurrence of diarrhea when disaccharides are not hydrolyzed in the gut?

    <p>Deficiency of the appropriate enzyme (D)</p> Signup and view all the answers

    Which of the following best describes homopolysaccharides?

    <p>Polymers of a single monosaccharide (C)</p> Signup and view all the answers

    Starch is composed of which two polymeric units of glucose?

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

    What is the process called that converts glucose into glycogen?

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

    During postmortem, at what pH does glycogenolysis cease due to lactic acid formation?

    <p>5.5 (C)</p> Signup and view all the answers

    Which monosaccharide is primarily synthesized in the mammary gland to produce lactose?

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

    Which of the following correctly defines dextrins?

    <p>Products of starch partially hydrolyzed (A)</p> Signup and view all the answers

    What type of sugar is formed if the remaining —OH group is on the left side during the cyclic reaction?

    <p>β-sugar (D)</p> Signup and view all the answers

    Where is glycogen primarily stored in higher animals?

    <p>In the liver and muscles (C)</p> Signup and view all the answers

    What distinguishes a sugar that has an asymmetric carbon atom?

    <p>It shows optical isomerism (B)</p> Signup and view all the answers

    What type of polysaccharide denotes carbohydrates with additional molecular groups, such as hexuronic acid?

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

    Which monosaccharide is commonly found in seminal fluid and provides energy for sperm?

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

    Which cyclic form corresponds to a 5-carbon ring structure?

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

    Which of the following carbohydrates is formed from glucose in the liver?

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

    A compound that can rotate plane polarized light either to the right or to the left exhibits what property?

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

    Which monosaccharide does NOT occur freely in nature?

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

    Which type of isomerism pertains to compounds with the same molecular formula but different functional groups?

    <p>Aldose-Ketose isomerism (C)</p> Signup and view all the answers

    What distinguishes an anomer from regular stereoisomers?

    <p>It specifically involves the position of the hydroxyl group at an anomeric carbon in ring structures. (B)</p> Signup and view all the answers

    Which monosaccharide is known to be dextrorotatory and is often referred to as dextrose?

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

    Which of the following statements about epimers is correct?

    <p>They are isomers differing in the position of the hydroxyl group at only one asymmetric carbon. (D)</p> Signup and view all the answers

    How many asymmetric carbon atoms are present in fructose?

    <p>3 (D)</p> Signup and view all the answers

    Which sugar is considered a deoxy sugar and is a component of nucleic acids?

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

    Which of the following molecules is an enantiomer of glyceraldehyde?

    <p>L-glyceraldehyde (C)</p> Signup and view all the answers

    Alpha and beta forms of glucose are examples of what type of isomers?

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

    Flashcards

    What are trioses?

    Monosaccharides with three carbon atoms.

    What is an aldotriose?

    A triose with an aldehyde group.

    What is a ketotriose?

    A triose with a ketone group.

    What are tetroses?

    Monosaccharides with four carbon atoms.

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    What is an aldotetrose?

    A tetrose with an aldehyde group.

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    What is a ketotetrose?

    A tetrose with a ketone group.

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    What are pentoses?

    Monosaccharides with five carbon atoms.

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    What is an aldopentose?

    A pentose with an aldehyde group.

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    Enantiomers

    A molecule that can exist in two forms that are mirror images of each other.

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    Glyceraldehyde

    The simplest carbohydrate with one asymmetric carbon, resulting in two optically active forms.

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    Anomeric Carbon

    The asymmetric carbon atom that arises from the carbonyl group in aldoses (C1) and ketoses (C2).

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    Anomers

    Isomers formed due to the change in position of the hydroxyl group attached to the anomeric carbon. Examples include α and β glucose, and α and β fructose.

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    Aldose-Ketose Isomerism

    Isomers with the same molecular formula but differing in their functional group. For example, glucose (aldehyde) and fructose (ketone).

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    Epimers

    Isomers that differ at only one specific asymmetric carbon atom. Examples include glucose and mannose (at carbon 2), and glucose and galactose (at carbon 4).

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    Deoxy Sugars

    Sugars where a hydroxyl group is replaced by a hydrogen atom, meaning one oxygen atom is missing. Examples include deoxyribose (found in DNA) and 6-deoxy-L-galactose (found in glycoproteins).

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    Dextrorotatory

    A substance that rotates plane-polarized light to the right.

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    Amino Sugars

    Sugars containing an amino group (NH2) in their structure.

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    Glucosamine

    An amino sugar that is a key component of heparin and hyaluronic acid.

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    Galactosamine

    An amino sugar that forms part of chondroitin sulfate, a vital component of cartilage.

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    Mannosamine

    An amino sugar commonly found in neuraminic and sialic acids.

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    Muramic Acid

    A derivative of glucosamine, found in the cell walls of most bacteria, providing structural support.

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    Glycosides

    Compounds formed when a carbohydrate and a non-carbohydrate component are linked together by an acetal linkage.

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    Invert Sugar

    A sugar that contains equal parts glucose and fructose. Found in honey.

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    Sucrase (Invertase)

    The enzyme that hydrolyzes sucrose into glucose and fructose, producing invert sugar.

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    Glucose: Primary Energy Source

    The primary energy source for all cells in the body, used directly by erythrocytes (red blood cells) and brain cells.

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    Glucose Metabolism in the Liver

    In the liver, glucose is converted into other carbohydrates like glycogen for energy storage and galactose for different bodily functions.

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    Fructose: The Fruit Sugar

    A simple sugar found in fruits, honey, and semen. It is converted into glucose in the liver, providing energy for sperm cells primarily.

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    Galactose: Milk Sugar

    Produced by the mammary glands to form lactose, the sugar in milk. It's also found in agar, glycosaminoglycans, and glycolipids.

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    Mannose: A Glycoprotein Component

    Does not exist freely in nature and contributes to the structure of many glycoproteins.

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    Cyclic Sugars: Furanose and Pyranose

    A cyclic form (ring shape) of a sugar molecule, formed when the carbonyl group (C=O) reacts with an alcohol (-OH) group.

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    Alpha (α) and Beta (β) Sugars

    The position of the remaining hydroxyl group (-OH) determines whether a sugar is alpha (α) or beta (β).

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    Asymmetric Carbon in Sugars

    A carbon atom linked to four different groups or atoms, leading to optical activity and isomerism in sugars.

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    What are polysaccharides?

    Polysaccharides are complex carbohydrates composed of many monosaccharide units linked together.

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    What are homopolysaccharides?

    Homopolysaccharides are polysaccharides made up of only one type of monosaccharide.

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    What are heteropolysaccharides?

    Heteropolysaccharides are polysaccharides made up of different types of monosaccharides or other groups like hexuronic acid.

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    What is starch?

    Starch is a homopolysaccharide made of glucose units, serving as a primary energy storage in plants.

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    What are amylose and amylopectin?

    Amylose and amylopectin are the two types of glucose polymers that make up starch, differing in their structure and properties.

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    What is glycogen?

    Glycogen is the main energy storage polysaccharide in animals, similar in structure to amylopectin.

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    What are glycogenesis and glycogenolysis?

    Glycogenesis is the process of converting glucose into glycogen for storage, while glycogenolysis is the breakdown of glycogen back into glucose for energy.

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    What are dextrins?

    Dextrins are smaller, partially broken-down products of starch formed by hydrolysis.

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    Dextrins

    Dextrins are a type of polysaccharide made up of smaller, fragmented units of starch. They form sticky, gummy masses and are used in various applications, including food, adhesives, and medicines.

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    Types of Dextrins: Amylodextrin, Erythrodextrin, Achrodextrin

    The three types of dextrins are categorized based on their structure and how they interact with iodine. Amylodextrins are straight and resemble starch, Erythrodextrins are branched, and Achrodextrins are smaller and unbranched versions of amylodextrins.

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    Limit Dextrin

    A well-defined dextrin formed when starch is broken down by β-Amylase. No further action can be observed after β-Amylase has finished working on it.

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    Cellulose

    Cellulose is a long, straight chain of glucose units linked together by β 1-4 glycosidic bonds. It is undigestible by humans due to the absence of an enzyme that can break down the β-linkage.

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    Agar

    A homopolysaccharide composed of repeated units of sulphated galactose. It is found in seaweed and has various uses in medicine and microbiology.

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    Inulin

    A homopolysaccharide made up of repeating fructose units linked by β1-2 bonds. It is found in plants like artichokes and onions. It's used in medical tests to assess kidney function and fluid volume.

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    Study Notes

    Carbohydrate Chemistry

    • Carbohydrates are defined chemically as aldehyde or ketone derivatives of higher polyhydric alcohols, or compounds that yield these derivatives upon hydrolysis.
    • Carbohydrates are a primary energy source.
    • Carbohydrates are components of compound lipids and conjugated proteins.
    • Degradation products of carbohydrates act as catalysts.
    • Some carbohydrate derivatives serve as drugs (e.g., cardiac glycosides, antibiotics).
    • Lactose is the primary milk sugar in lactating mammary glands.
    • Degradation products are used in synthesizing other substances (e.g., fatty acids, cholesterol, amino acids).
    • Carbohydrates are components of mucopolysaccharides, which form the ground substance of mesenchymal tissues.
    • Inherited deficiencies in carbohydrate metabolism enzymes can cause diseases (e.g., galactosemia, glycogen storage diseases, lactose intolerance).
    • Disruptions in glucose metabolism are linked to diabetes mellitus.

    Carbohydrate Classification

    • Carbohydrates are categorized into four major groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
    • Monosaccharides contain one sugar unit, and cannot be further hydrolyzed.
      • Subdivided based on the number of carbon atoms (e.g., trioses, tetroses, pentoses, hexoses).
      • Further subdivided into aldoses (aldehyde group) and ketoses (ketone group).
      • Examples include: - Triose: Glyceraldehyde, Dihydroxyacetone - Tetroses: Erythrose, Erythrulose - Pentoses: Ribose, arabinose, lyxose, xylose - Hexoses: Glucose, mannose, galactose, fructose
    • Disaccharides contain two sugar units.
    • Oligosaccharides contain 3–10 sugar units.
    • Polysaccharides contain more than 10 sugar units.

    Monosaccharides

    • Monosaccharides (also called simple sugars or glycoses) cannot be further hydrolyzed into simpler forms.
    • They can be further classified according to the number of carbon atoms (trioses, tetroses, pentoses, hexoses, etc) and by the presence of an aldehyde or ketone group (aldoses or ketoses).
    • Specific monosaccharides, such as ribose, have important roles in the structure of nucleic acids (RNA and DNA), ATP, GTP, and coenzymes NAD and FAD.
    • Arabinose is found in fruits. Ingesting large quantities can cause arabinose to appear in urine.
    • Lyxose is a human heart muscle constituent.
    • The classification of monosaccharides are based on the number of carbon atoms.
    • Hexoses are six-carbon monosaccharides including Glucose, mannose, galactose and fructose. Glucose is the major energy source in mammals and fetus.

    Cyclic Structures of Monosaccharides

    • Monosaccharides exist primarily in cyclic forms produced by the reaction between the carbonyl group and an alcohol group.
    • Furanose structures have a four-membered ring.
    • Pyranose structures have a five-membered ring.
    • Different arrangements around the hemiacetal or hemiketal carbons(α or β) produce anomers.
    • α and β designations are made based on the position of the hydroxyl group attached to the anomeric carbon in the ring structure.
    • Asymmetric carbons exist in the monosaccharides and this gives rise to the optical activity and isomers.

    Properties of Monosaccharides

    • Optical activity - Monosaccharides can rotate polarized light either to the left (levo) or right (dextro).
    • Optical isomerism - Several forms of the same monosaccharide can be mirror images (e.g., D- and L- forms of glyceraldehyde).

    Important Monosaccharides and Derivatives

    • Deoxy sugars- One or more oxygen atoms have been replaced with hydrogen. Example: Deoxyribose (a component of DNA)
    • Amino sugars: Monosaccharides containing an amino group (-NH2) . Example: Glucosamine, Galactosamine, Mannosamine.
    • Neuraminic acid (or Sialic acids)- A derivative of an amino sugar containing an acidic group and linked to other components. The presence of N-acetyl group makes them stable.
    • Glycosides: Contains a carbohydrate and a non-carbohydrate residue linked. Example: Cardiac glycosides like Digitalis (used in heart conditions).

    Disaccharides

    • Disaccharides contain two monosaccharide units linked together by a glycosidic bond.
    • Common Disaccharides: Maltose, Isomaltose, Trehalose, Lactose and Sucrose
    • Invert sugar is a mixture of glucose and fructose synthesized by the hydrolysis of sucrose in the presence of sucrase enzyme.

    Polysaccharides

    • Polysaccharides are polymers of monosaccharides.
    • Homopolysaccharides contain only one type of monosaccharide unit. Examples include: Starch, Glycogen, Cellulose, Agar, Inulin.
    • Heteropolysaccharides contain more than one type of monosaccharide unit; examples include: Mucopolysaccharides.

    Starch

    • Starch is a storage carbohydrate in plants, composed of amylose and amylopectin.
    • Amylose is a linear polymer of glucose units.
    • Amylopectin is a branched polymer of glucose units.
    • Starch can be broken down into dextrins through partial hydrolysis by acids or enzymes..

    Glycogen

    • Glycogen is the storage form of carbohydrates in animals, similar to starch in structure but more branched.

    Dextrins

    • Dextrins are products of starch partial hydrolysis, and have lower molecular weights.
    • Various types of dextrins exist, based on the degree of hydrolysis.

    Cellulose

    • Cellulose is a structural carbohydrate in plants, composed of long chains of glucose units linked by β(1 → 4) glycosidic bonds.
    • It is indigestible by humans due to the lack of enzymes to break down the β-linkages.

    Agar

    • Agar is a homopolysaccharide derived from seaweed.
    • It is used as a laxative and in microbiology for culturing bacteria.

    Inulin

    • Composed of fructose units linked by β(2 → 1) bonds.
    • Used in diagnostic tests of glomerular filtration rate (GFR).

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