Biochemistry: Saccharides Chemistry & Function Quiz
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Questions and Answers

Which of the following is a function of saccharides/carbohydrates?

  • Source of energy (correct)
  • Production of vitamins
  • Memory storage
  • Hormone regulation

    • Monosaccharides can exist only in cyclic form.

    False

    What suffix is used for saccharides?

    ose

    Monosaccharides containing an aldehyde group are classified as __________.

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

    Match the type of saccharide with their examples:

    <p>Monosaccharides = Glucose Disaccharides = Sucrose Oligosaccharides = Raffinose Polysaccharides = Starch</p> Signup and view all the answers

    Which configuration of monosaccharides has the hydroxyl group to the right of the last stereocenter carbon?

    <p>D configuration</p> Signup and view all the answers

    All ketoses are classified as reducing sugars.

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

    What are the two forms of pentoses and hexoses?

    <p>Cyclic and non-cyclic</p> Signup and view all the answers

    What is formed when two monosaccharides join together?

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

    Ketoses cannot reduce Cu2+.

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

    What are enantiomers?

    <p>Mirror images of one another that are non-superimposable.</p> Signup and view all the answers

    The anomeric carbon of an aldose is at ___ atom.

    <p>C1</p> Signup and view all the answers

    Match the types of isomers with their definitions:

    <p>Isomers = Same molecular formula, different structures Stereoisomers = Same order of atoms but different spatial arrangement Anomers = Isomers differing at the anomeric carbon Optical isomers = Enantiomers that differ in light rotation</p> Signup and view all the answers

    Which statement about optical isomers is true?

    <p>One enantiomer rotates light clockwise while the other rotates it counterclockwise.</p> Signup and view all the answers

    Lactose can be absorbed directly into the bloodstream without any modification.

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

    What is the role of lactase in infants?

    <p>It catalyzes the hydrolysis of lactose into glucose and galactose.</p> Signup and view all the answers

    What type of bond joins monosaccharides together in oligosaccharides?

    <p>O-glycosidic bond</p> Signup and view all the answers

    Glycosides can test positive with Benedict’s reagent.

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

    What is the main characteristic of a hemiacetal compared to an acetal?

    <p>A hemiacetal can act as a reducing agent, while an acetal cannot.</p> Signup and view all the answers

    The polysaccharide composed of one type of sugar monomer is called a _________.

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

    Match the sugar derivatives with their descriptions:

    <p>Sugar alcohols = Class of polyols with sweetening power Amino sugars = Sugars with an amino group Sugar phosphates = Sugars with added phosphate groups Glycosides = Formed from sugar and aglycone</p> Signup and view all the answers

    Which polysaccharide is known for being a polymer of glucose?

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

    Lactose intolerance is related to the inability to digest polysaccharides.

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

    What is an example of a heteropolysaccharide?

    <p>Hyaluronic acid or chondroitin sulfate</p> Signup and view all the answers

    Which of the following statements about glycogen is true?

    <p>It functions as the primary carbohydrate storage molecule in animal cells.</p> Signup and view all the answers

    Cellulose is composed of glucose units linked by α(1,4) glycosidic bonds.

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

    What is the main function of starch in plant cells?

    <p>Energy reservoir</p> Signup and view all the answers

    Glycosaminoglycans are a type of ______ that provide extracellular support for organisms.

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

    Match the following polysaccharides with their primary function:

    <p>Glycogen = Carbohydrate storage in animals Starch = Energy reservoir in plants Cellulose = Structural component of plant cell walls Glycosaminoglycans = Extracellular support for organisms</p> Signup and view all the answers

    What type of bond links the glucose units in cellulose?

    <p>β(1,4) glycosidic bonds</p> Signup and view all the answers

    Amylose is a branched form of starch.

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

    What distinguishes amylopectin from amylose?

    <p>It has branch points and is a branched polymer.</p> Signup and view all the answers

    Study Notes

    Saccharides Chemistry & Function

    • Saccharides, also known as carbohydrates, are molecular compounds primarily composed of carbon (C), hydrogen (H), and oxygen (O) atoms, with a ratio of (CH₂O)ₙ.
    • Saccharides are formed during photosynthesis.
    • The suffix "-ose" typically indicates a saccharide.

    Saccharides/Carbohydrates

    • Saccharides are molecular compounds consisting of carbon (C), hydrogen (H), and oxygen (O).
    • The ratio of elements is typically (CH₂O)ₙ.
    • Formed during photosynthesis.
    • "-ose" is a common suffix used for saccharides.

    Functions of Saccharides

    • Source of energy for the body (e.g., glucose).
    • Energy storage in plants (e.g., starch).
    • Structural components in plants and insects (e.g., cellulose and chitin).
    • Components of other molecules (e.g., DNA, RNA, glycolipids, glycoproteins, ATP).
    • Precursors in the production of other biomolecules (e.g., amino acids, lipids).

    Classification of Saccharides

    • Monosaccharides: simple sugars.
    • Disaccharides: two monosaccharides joined together.
    • Oligosaccharides: three to ten monosaccharides joined together.
    • Polysaccharides: many monosaccharides joined together.

    Monosaccharides

    • The simplest carbohydrates, often called simple sugars.
    • General molecular formula (CH₂O)ₙ, where n = 3, 4, 5, or 6.
    • Triose (n=3), e.g., glyceraldehyde
    • Pentoses (n=5), e.g., ribose, deoxyribose
    • Hexoses (n=6), e.g., fructose, glucose, galactose

    D versus L Configuration

    • D configuration: the hydroxyl group on the chiral carbon furthest from the carbonyl group is on the right side in a Fischer projection.
    • L configuration: the hydroxyl group on the chiral carbon furthest from the carbonyl group is on the left side in a Fischer projection.
    • D or L is often used as a prefix when naming a carbohydrate.

    Cyclic Forms of Monosaccharides

    • Pentoses and hexoses can exist in two forms: cyclic (closed chain) and non-cyclic (open chain).
    • The cyclic form can be either a five-membered ring (furanose) or a six-membered ring (pyranose).
    • The open chain form of monosaccharides is illustrated with Fischer projections.
    • A Haworth projection represents the cyclic form of a monosaccharide.

    Aldoses and Ketoses

    • Aldoses: monosaccharides containing an aldehyde group.
    • Ketoses: monosaccharides containing a ketone group.
    • Ketoses must tautomerize to aldoses to act as a reducing sugar.

    Keto-enol Tautomerism

    • Monosaccharides exist in equilibrium between cyclic hemiacetal and open chain forms.
    • Tautomerism: a molecule that readily interconverts with each other by the movement of a hydrogen atom.
    • In the open chain form, the aldehyde function is oxidized by Cu²⁺.

    Isomers

    • Isomers: compounds with the same molecular formula but different chemical structures.
    • Stereoisomers: compounds that have the same molecular formula but different spatial arrangement of atoms.
    • Geometric isomers: stereoisomers that differ in the arrangement of groups around a double bond, such as in cis-trans isomers.

    Anomers

    • Anomers: isomers differing at the anomeric carbon atom (C-1 for aldoses, C-2 for ketoses).
    • α & β Anomers differ at the position of the OH group at C-1.
    • α anomer: OH group is on the opposite side of C-6 in a Haworth projection.
    • β anomer: OH group is on the same side as C-6 in a Haworth projection.

    Optical Isomers (Enantiomers)

    • Enantiomers: pairs of molecules that are mirror images of each other, but are non-superimposable.
    • Dextrorotatory: rotates plane polarized light clockwise.
    • Levorotatory: rotates plane polarized light counterclockwise.
    • A molecule that is non-superimposable on its mirror image is chiral.

    Chiral Carbon

    • A chiral carbon atom has four different atoms or groups bonded to it.
    • Most biological molecules contain at least one chiral carbon.

    Properties of Enantiomers

    • Identical chemical properties (e.g., boiling point, melting point, solubility)
    • Different biological activities (e.g., enzymes may only recognize one isomer)

    Example of the importance of optical isomers in Drug Design

    • Many drugs are optically active, meaning only one enantiomer (e.g., (-)-thalidomide) has the beneficial effect, while the other enantiomer can be harmful (e.g., (+)-thalidomide)

    Disaccharides

    • Formed by joining two monosaccharides via an O-glycosidic bond
    • Examples: maltose, cellobiose, lactose, sucrose

    Oligosaccharides

    • Molecules of 3-10 monosaccharides linked together.
    • Examples: raffinose, stachyose

    Sugar Derivatives

    • Organic compounds including sugar alcohols (e.g., sorbitol, mannitol).
    • Often used as sweeteners, but with varying sweetness compared to monosaccharides.
    • Also includes amino sugars (e.g., glucosamine, galactosamine).
    • Amino sugars have an amino group (-NH₂) substituted for a hydroxyl group (-OH) on the sugar molecule.

    Sugar Phosphates

    • Sugars with phosphate groups attached.
    • Important in biological energy transfer and storage.
    • Building blocks for DNA and RNA.

    Glycosides

    • Formed when a sugar molecule reacts with another molecule (non-sugar molecule).
    • Acetals do not undergo oxidation, and only hemiacetals are reducing agents.

    Nucleosides

    • A sugar (pentose) linked to a nitrogenous base (aglycone)
    • Adenosine is an example

    Polysaccharides

    • Long chains of monosaccharides linked through glycosidic bonds.
    • Classified as homopolysaccharides (one type of monomer) or heteropolysaccharides (more than one type of monomer).

    Examples of Homopolysaccharides

    • Glycogen: major carbohydrate storage molecule in animal cells.
    • Starch: major carbohydrate storage molecule in plants, present in two forms: amylose and amylopectin,.
    • Cellulose: structural component of plant cell walls, providing support and protection.

    Examples of Heteropolysaccharides

    • Glycosaminoglycans (GAGs)
    • Murein (or peptidoglycan): major component of bacterial cell walls

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    Saccharide Chemistry & Function PDF

    Description

    Test your knowledge on saccharides and carbohydrates with this quiz. Questions cover the structure, classification, and functions of monosaccharides, as well as the concepts of optical isomers and glycosidic bonds. Enhance your understanding of essential biochemical components.

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