Carbohydrates Quiz: Structure and Functions
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What is the primary role of carbohydrates in the body?

  • Source of energy (correct)
  • Building blocks of proteins
  • Storage of genetic information
  • Structural components of cell membranes

    • Which type of carbohydrate is glucose categorized as?

  • Monosaccharide (correct)
  • Pentose
  • Polysaccharide
  • Disaccharide

    • Galactose can be converted into which other sugar in the liver?

  • Fructose
  • Mannose
  • Sucrose
  • Glucose (correct)

    • Which monosaccharide is known as the sweetest sugar?

    <p>Fructose</p> Signup and view all the answers

    What is the primary characteristic of substances containing an asymmetric carbon atom?

    <p>Optical isomerism</p> Signup and view all the answers

    What is glyceraldehyde commonly referred to as?

    <p>Reference sugar</p> Signup and view all the answers

    Which of the following carbohydrates cannot be synthesized in the liver?

    <p>Lactose</p> Signup and view all the answers

    Which carbohydrate is produced from the hydrolysis of starch?

    <p>Glucose</p> Signup and view all the answers

    What term is used to describe a substance that rotates plane polarized light to the left?

    <p>Levorotatory</p> Signup and view all the answers

    How many asymmetric carbon atoms are present in glucose?

    <p>4</p> Signup and view all the answers

    Which type of isomerism describes substances with the same molecular formula but different structures due to atom arrangement?

    <p>Structural isomerism</p> Signup and view all the answers

    What is the formula to calculate the number of stereoisomers based on asymmetric carbon atoms?

    <p>$2^n$</p> Signup and view all the answers

    Which of the following substances is classified as a levorotatory sugar?

    <p>Fructose</p> Signup and view all the answers

    Which type of isomerism compares compounds like glucopyranose and glucofuranose?

    <p>Ring isomerism</p> Signup and view all the answers

    In D and L isomerism, where is the OH group located in the D form?

    <p>To the right of the sub-terminal carbon</p> Signup and view all the answers

    Which of the following is NOT a type of stereo-isomerism?

    <p>Ring isomerism</p> Signup and view all the answers

    What type of sugar is formed from the linkage of the anomeric carbons of glucose and fructose?

    <p>Non-reducing sugar</p> Signup and view all the answers

    What happens to the optical rotation of glucose and fructose when they are hydrolyzed?

    <p>It becomes levorotatory</p> Signup and view all the answers

    Which enzyme is also referred to as invertase?

    <p>Sucrase</p> Signup and view all the answers

    Which feature is NOT characteristic of the sugar formed from glucose and fructose linkage?

    <p>It is mutarotating</p> Signup and view all the answers

    What type of linkage is present in trehalose?

    <p>α-1,1-glucosidic linkage</p> Signup and view all the answers

    What type of glycosidic linkage is present in sucrose?

    <p>Alpha 1-2 linkage</p> Signup and view all the answers

    What two monosaccharides make up sucrose?

    <p>α Glucose and β Fructose</p> Signup and view all the answers

    Which of the following is classified as a non-reducing sugar?

    <p>Sucrose</p> Signup and view all the answers

    What is the glycosidic linkage present in lactose?

    <p>Beta 1-4 linkage</p> Signup and view all the answers

    What glycosidic linkage is found in maltose?

    <p>Alpha 1-4 linkage</p> Signup and view all the answers

    What are the products of hydrolysis of maltose?

    <p>Glucose only</p> Signup and view all the answers

    Hydrolysis of lactose results in which of the following?

    <p>Glucose and Galactose</p> Signup and view all the answers

    What type of polysaccharide yields only one type of monosaccharide upon hydrolysis?

    <p>Homopolysaccharides</p> Signup and view all the answers

    Which type of protein is characterized by having an axial ratio greater than 10?

    <p>Fibrous proteins</p> Signup and view all the answers

    Which characteristic is true about proteins of high biological value?

    <p>They contain all 10 essential amino acids in balanced amounts.</p> Signup and view all the answers

    What distinguishes derived proteins from simple and conjugated proteins?

    <p>They are created from hydrolysis of other proteins.</p> Signup and view all the answers

    What type of proteins are most plant proteins categorized as?

    <p>Proteins of low biological value</p> Signup and view all the answers

    Which of the following examples is classified as a globular protein?

    <p>Albumin</p> Signup and view all the answers

    Which protein is deficient in tryptophan and cysteine?

    <p>Collagen</p> Signup and view all the answers

    How are albumins and globulins differentiated based on their solubility?

    <p>Both are soluble but differ in salt solutions.</p> Signup and view all the answers

    Which protein class is prone to being soluble and motile?

    <p>Globular proteins</p> Signup and view all the answers

    Which sugar is formed from β-galactose and β-glucose linked by a 1,4-glucosidic linkage?

    <p>Lactose</p> Signup and view all the answers

    What is a key benefit of lactose as a sweetener for infants?

    <p>It prevents constipation in infants.</p> Signup and view all the answers

    Which of the following sugars is a reducing disaccharide?

    <p>Maltose</p> Signup and view all the answers

    What type of linkage is present in cellobiose?

    <p>β-1,4-linkage</p> Signup and view all the answers

    Which sugar is primarily known as table sugar and is formed from α-glucose and β-fructose?

    <p>Sucrose</p> Signup and view all the answers

    Which property of lactose makes it suitable for baby feeding compared to other sugars?

    <p>It is non-fermentable and does not produce gas.</p> Signup and view all the answers

    What advantage does unabsorbed lactose provide for infants?

    <p>It serves as food for intestinal bacteria.</p> Signup and view all the answers

    Which of the following sugars is non-fermentable and does not cause colic in infants?

    <p>Lactose</p> Signup and view all the answers

    Study Notes

    Biochemistry of Carbohydrates

    • Carbohydrates are substances containing carbon, hydrogen, and oxygen.
    • They are aldehyde (CHO) or ketone (C=O) derivatives of polyhydric alcohols (with more than one OH group) or compounds that yield these derivatives on hydrolysis.

    Importance of Carbohydrates

    • Chief source of energy.
    • Important structural components in animal and plant cells.
    • Important part of nucleic acids, free nucleotides, and coenzymes.
    • Major antigens (e.g., blood group substances) are carbohydrates.
    • Have a biological role as parts of hormones, their receptors, and enzymes.

    Classification of Carbohydrates

    • Monosaccharides: Contain one sugar unit (cannot be hydrolyzed).
    • Disaccharides: Contain two sugar units.
    • Oligosaccharides: Contain 3-10 sugar units.
    • Polysaccharides: Contain more than 10 sugar units.

    Monosaccharides

    • The simplest units of carbohydrates containing one sugar unit.
    • General formula: Cn(H2O)n
    • Naming:
      • Based on functional groups: Aldoses (aldehyde group -CHO) and Ketoses (ketone group -C=O).
      • Based on the number of carbon atoms: Trioses (3C), Tetroses (4C), Pentoses (5C), Hexoses (6C).
        • Aldotrioses/Ketotrioses, Aldotetroses/Ketotetroses, Aldopentoses/Ketopentoses, Aldohexoses/Ketohexoses

    Classification of Monosaccharides

    • Trioses:

      • Aldotrioses: Glyceraldehyde ("glycerose").
      • Ketotrioses: Dihydroxyacetone.

    • Tetroses:

      • Aldotetroses and ketotetroses. (e.g., Erythrose, Erythrulose)

    • Pentoses:

      • Aldopentoses (e.g., Ribose, arabinose, xylose, lyxose).
      • Ketopentoses (e.g., Ribulose, xylulose).
        • Important functions of pentoses:
          • Component of nucleic acids (RNA and DNA).
          • Component of ATP, GTP.
          • Component of coenzymes NAD, NADP, and FAD.

    • Hexoses:

      • Aldohexoses: glucose, mannose, galactose.
      • Ketohexose: fructose.
        • Important functions of glucose:
          • Most important carbohydrate sugar; "grape sugar."
          • Main sugar in blood.
          • Major energy source.
          • Converted to glycogen, galactose, etc.
        • Important functions of galactose:
          • Converted to glucose in the liver.
          • Major component of lactose. -Important functions of fructose:
          • "Fruit/semen sugar."
          • Sweetest sugar.
          • Part of honey and fruits. -Important functions of mannose -Part of glycoproteins and sialic acid -Found in plant mannans

    Ring (Cyclic) Structure of Sugars

    • Due to reaction between C=O (carbonyl) of an aldehyde group in aldoses or of a ketone group in ketoses with an alcoholic hydroxyl group.
    • Furanose: 4-carbon ring.
    • Pyranose: 5-carbon ring.

    Optical Activity

    • Ability of a substance to rotate plane-polarized light.
    • Dextrorotatory (d or +): rotates light to the right.
    • Levorotatory (l or -): rotates light to the left.
    • Glucose is dextrorotatory, some use the name dextrose.
    • Fructose is levorotatory, sometimes called levulose.

    Optical Isomerism

    • Ability of a substance to exist in more than one form (isomer).
    • Structural isomerism involves different atoms or groups' arrangement into different patterns.
    • Stereoisomerism involves the spatial configuration (arrangement) of atoms or groups in space.

    Structural Isomerism

    • Different arrangement of atoms and groups forming the molecule (e.g., ring vs. straight chain).

    Stereoisomerism

    • D- and L- isomerism (enantiomers): Differ in distribution of H and OH.
    • Anomers: Stereoisomers differing in arrangement around anomeric carbon after cyclization
    • Epimers: Stereoisomers differing in arrangement around a single non-anomeric carbon.

    Sugar Derivatives

    • Sugar acids (e.g., gluconic, glucuronic, saccharic acids).
    • Sugar alcohols (e.g., sorbitol).
    • Deoxy sugars (e.g., deoxyribose).
    • Amino sugars (e.g., glucosamine, galactosamine).

    Disaccharides

    • Maltose, isomaltose, cellobiose, lactose, sucrose, trehalose.

    • Reducing disaccharide: Maltose, Isomaltose, Cellobiose, and Lactose.

    • Non-reducing disaccharide: Sucrose & Trehalose

    • Important properties of reducing disaccharides include acting as a reducing agent, and forming osazone crystals.

    Polysaccharides

    • Contain more than 10 monosaccharide units, and yield monosaccharides upon acid hydrolysis.
    • Classified into homopolysaccharides (one type of monosaccharide) and heteropolysaccharides (more than one type of monosaccharide).
      • Homopolysaccharides include:
        • Glucosans: Starch, Dextrins, Dextran, Glycogen, Cellulose.
        • Fructosans: Inulin.
        • Galactosans: Agar-agar.
        • N-acetyl-glucosan: Chitin.

    Heteropolysaccharides

    • Contain different sugar units.
    • Include glycosaminoglycans (mucopolysaccharides).
      • Criteria for glycosaminoglycans: repeating disaccharide units w/ acidic sugar - amino sugar.
      • Often contain sulfate groups.
      • Unbranched.
      • Mostly extracellular (except heparin).
      • Components of connective tissue (bone, elastin and collagen). -Act as lubricants and cushions
        • Classification into sulfur free & containing (e.g., hyaluronic acid, chondroitin, keratan sulfate, heparin, and heparan sulfate).

    Conjugated Carbohydrates

    • Simple protein + non-protein group (prosthetic group)
      • Glycoproteins, Glycolipids, and Proteoglycans.

    Derived Carbohydrates

    • Result of protein denaturing or hydrolysis -Primary & Secondary

    Biochemistry of Proteins

    • Objectives
      • Amino acids
      • Peptides
      • Protein.
      • Methods of precipitation of proteins
      • Separation techniques for proteins and amino acids

    Amino acids

    • Structural units of proteins.
    • Obtained from proteins by hydrolysis.
    • General formula:
      • α (alpha) carbon
      • Amino group (-NH2)
      • Carboxyl group (-COOH)
      • Hydrogen atom (H)
      • Side Chain/Radical group (R)
    • About 300 amino acids exist in nature, but only 20 polymerize to form proteins in mammals.
    • All amino acids in mammals are L-amino acids. D-amino acids are found in bacteria.
    • Amino acids are optically active (except glycine).
    • Amino acids are amphoteric (react as both an acid and a base).

    Classification of Amino Acids

    • Chemical Classifications based on R group Properties

      • Neutral
      • Acidic
      • Basic
      • Special amino acids

    • Nutritional Classifications based on essential/non-essential needs

      • Essential
      • Non essential
      • Semi-essential

    • Metabolic classifications based on ability to be catabolized

      • Ketogenic & Glucogenic

    Peptides

    • Formed from linking amino acids via peptide bonds.
    • Dipeptide (2 amino acids).
    • Tripeptide (3 amino acids)
    • Oligopeptide (3-10 amino acids).
    • Polypeptide (10-50 amino acids).
    • Glutathione (tripeptide):
      • Glutamyl-cysteinyl-glycine
      • Functions in detoxification, maintaining redox balance, and amino acid transport.

    Proteins

    • Polymers formed predominantly by amino acids linked via peptide bonds.
    • Molecular weight usually greater than 50 amino acids.
    • Can contain other atoms/ions in addition to N, C, H, O (e.g., S, P, metals).

    Methods of Precipitation of Proteins

    • At the isoelectric point (proteins have neutral net charge).
    • By various concentrations of salt solutions (salting out).
    • By heavy metals (protein denaturation).
    • By alkaloid reagents (protein denaturation).
    • By alcohol precipitation (protein denaturation).
    • By heat coagulation (protein denaturation).

    Separation techniques for proteins and amino acids

    • Electrophoresis: Movement of charged molecules in an electric field.
    • Chromatography: Separation based on different properties.
    • Precipitation: Removal by precipitation with various agents.
    • Ultracentrifugation: Separation by density.
    • Dialysis: Separation by size/weight through a semi-permeable membrane.
    • Precipitation by antibodies: Utilizing the specificity of antibodies to precipitate particular protein.

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    Test your knowledge on carbohydrates with this quiz, which covers their roles in the body, types, and unique characteristics. Questions range from the structure of glucose to isomerism and sugar classifications. Perfect for students of biology and nutrition!

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