Secondary Metabolites in Plants
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Questions and Answers

What type of tannins consists of one or more sugars bonded to phenolic acid molecules?

  • Terpenoids
  • Condensed tannins
  • Saponins
  • Hydrolysable tannins (correct)

    • Sesquiterpenes are composed of two isoprene units.

    False

    What are the two types of cardiac glycosides mentioned?

    Cardenolides and bufadienolides

    Saponins are glycosides of ______ that are amphipathic.

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

    Match the following terpenoid types to their respective characteristics:

    <p>Monoterpenes = Widespread in essential oils Sesquiterpenes = Toxic and allergenic Diterpenes = Common in latex and resins Triterpenes = Medicinally important</p> Signup and view all the answers

    Which of the following compounds has a bitter taste and is astringent?

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

    Condensed tannins consist solely of sugars.

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

    What is the primary biological activity associated with monoterpenes?

    <p>Aromatic and antimicrobial</p> Signup and view all the answers

    Which of the following groups of secondary metabolites includes compounds that are known for their antibacterial and antifungal activity?

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

    All alkaloids are acidic in nature.

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

    What primary biological activity is associated with flavonoids?

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

    Phenolics are characterized by the presence of an aromatic ring plus one or more __________ substituents.

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

    Match the type of flavonoid with its characteristic:

    <p>Flavones = Type of flavonoid often found in flowers Flavonols = Antioxidant properties Flavanones = Found in citrus fruits Chalcones = Intermediate in flavonoid biosynthesis</p> Signup and view all the answers

    Which secondary metabolite group consists of compounds formed by linking isoprene units?

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

    Name the sulfur-containing compound that releases strong smelling volatile substances.

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

    Tannins are known to bind to proteins.

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

    Which type of compounds are known for their antioxidant properties and are examples of tetraterpenes?

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

    All terpenes have the same impact on membrane stability.

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

    What may happen if Na+, K+, or Ca++ channels are affected by terpenes?

    <p>Disturbances in signal transduction</p> Signup and view all the answers

    Terpenes can lead to cell death through uncontrolled efflux of ______.

    <p>ions and metabolites</p> Signup and view all the answers

    Match the following terpenes with their potential effect or property:

    <p>Geranial = Membrane activity and protein interaction Camphor = Potential narcotic effects Eucalyptol = Anti-inflammatory effects Harpagoside = Cytotoxic potential</p> Signup and view all the answers

    Which of the following statements is true regarding glycosides of triterpenes?

    <p>They are stored in vacuoles in an inactive form.</p> Signup and view all the answers

    Saponins can complex cholesterol in biomembranes.

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

    What effect do steroids, triterpenes, and saponins have due to their structural resemblance to endogenous hormones?

    <p>Anti-inflammatory effect</p> Signup and view all the answers

    Study Notes

    Major Groups of Secondary Metabolites

    • Plant secondary metabolites are divided into four major groups: Phenolics, Terpenoids, Sulfur compounds, Alkaloids and other nitrogen compounds.
    • Phenolics: Characterized by an aromatic ring with one or more hydroxyl substituents.
    • Terpenoids and steroids: Formed by the linking together of a number of five carbon isoprene units.
    • Alkaloids and other nitrogen containing compounds: All alkaloids are basic, nitrogen-containing substances with a nitrogen atom as part of a ring system.
    • Sulfur containing compounds: Enzymatically release strong smelling volatile sulfur compounds.

    Phenolics

    • Phenolics are widely distributed in plants and come in different chemical classes: Phenols, Flavonoids, Quinones, Tannins, and Lignins.
    • Flavonoids: Water-soluble pigments, contribute to a range of medicinal properties including strengthening vasculature, anti-inflammatory, anti-oxidant, anti-allergic, antibacterial and antiviral effects.
    • Quinones: Oxidized with –O in place of –OH, have antibacterial and antifungal activity.
    • Tannins: Polyphenolic macromolecules, bitter taste, and astringent, complex with proteins.
      • Hydrolysable tannins: Consists of one or more sugars bonded to phenolic acid molecules.
      • Condensed tannins: Made up of two or more flavonoid units.
    • Tannins have antiseptic effects due to their ability to complex with proteins and are often used to treat diarrhea.
    • Lignins: Indigestible to animals.

    Terpenoids

    • Terpenoids are classified into several distinct groups, including Monoterpenes, Sesquiterpenes, Sesquiterpene lactones, Diterpenes, Triterpenes, and Steroids.
    • Monoterpenes: Two isoprene units linked together, including essential oils.
    • Sesquiterpenes: Three isoprene units, examples include Helenalin.
    • Triterpenes: Approximately 30C, many are important in medicine.
    • Steroids: Biogenetically derived from C30 precursors, with modifications to the number of isoprene units, all have a common steroid skeleton.
    • Terpenes (mono, sesqui, di, and tri) have a number of similar biological activities.
      • Highly hydrophobic, readily interact with membranes.
      • Increase membrane fluidity leading to ion and metabolite efflux.
      • Can cause membrane protein conformational changes, affecting signal transduction.
      • Common functional groups:
        • Aldehydes: Form covalent bonds with protein amino groups.
        • Terminal exocyclic methylene groups: Couple to protein SH groups.
        • Inner oxides or peroxides: Chemically reactive and can bind to proteins.
    • Terpenes can have antimicrobial and cytotoxic effects against a wide range of organisms, but also toxicity at higher doses.

    Saponins

    • Saponins are glycosides of triterpenes with amphipathic properties.
    • Widely distributed in the plant kingdom, used as precursors in human hormone synthesis due to their structural similarity to human steroids.
    • Cardiac glycosides are steroidal glycosides with potent effects on the heart, with two types: cardenolides and bufadienolides.

    Other Terpenoids

    • Tetraterpenes: Large 40C, highly lipophilic compounds with antioxidant properties.
    • Polyterpenes: Very large molecules, common in latex.
    • Iridoids: Specific class of monoterpenes with the iridane skeleton.

    Glycosides of Triterpenes and Saponins

    • Water soluble and stored in an inactive form in the vacuole.
    • Converted to an active form exhibiting membrane activity when the plant is attacked.
    • Monodesmosidic saponins: Complex cholesterol in biomembranes, bind to glycoproteins and glycolipids.
    • Can cause membrane tension and leakage, contributing to their use in overcoming external infections.
    • Internal use at low doses due to toxicity.

    Steroids, Triterpenes, and Saponins

    • Resemble endogenous hormones.
    • Possess anti-inflammatory effects due to a corticomimetic effect.

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    Plants, Pharmaceuticals and Medicine PDF

    Description

    Explore the major groups of plant secondary metabolites including phenolics, terpenoids, sulfur compounds, and alkaloids. Each group has unique characteristics and medicinal properties that are vital in plant biology. This quiz will test your understanding of these essential compounds and their classifications.

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