Biology Chapter 9: Biomolecules
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Questions and Answers

What type of compounds are found in living organisms?

organic compounds

Which elements are found in both non-living matter and living tissues?

  • Oxygen and Sodium
  • Calcium and Magnesium
  • Carbon and Hydrogen (correct)
  • Nitrogen and Sulphur

    • All elements present in a sample of earth’s crust are also present in a sample of living tissue.

    True

    ___________ compounds are generally water insoluble.

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

    Match the following organic compounds with their classification:

    <p>Amino acids = Proteinaceous Fatty acids = Lipids Nucleosides = Nucleic acids</p> Signup and view all the answers

    What is the tertiary structure of a protein?

    <p>The long protein chain folded upon itself like a hollow woolen ball.</p> Signup and view all the answers

    What is the quaternary structure of a protein?

    <p>The arrangement of multiple polypeptides or subunits with respect to each other.</p> Signup and view all the answers

    What type of molecules are almost all enzymes?

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

    Enzymes isolated from thermophilic organisms are stable at high temperatures.

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

    What are compounds other than primary metabolites called?

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

    What is the most abundant chemical in living organisms?

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

    Lipids are strictly considered macromolecules.

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

    Proteins are linear chains of __________ linked by peptide bonds.

    <p>amino acids</p> Signup and view all the answers

    Match the following nucleotide components:

    <p>Heterocyclic compound = Nitrogenous bases (adenine, guanine, uracil, cytosine, thymine) Monosaccharide = Ribose or 2' deoxyribose Phosphoric acid = Phosphate</p> Signup and view all the answers

    What is the term for the temperature and pH at which an enzyme shows its highest activity?

    <p>Optimum temperature and pH</p> Signup and view all the answers

    What is the term used for the maximum velocity of an enzymatic reaction?

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

    What is the term for inhibition where the inhibitor closely resembles the substrate and competes for the substrate-binding site?

    <p>Competitive inhibition</p> Signup and view all the answers

    Enzymes are composed of one or several ______ chains.

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

    Match the enzyme classification with the type of reactions they catalyze:

    <p>Oxidoreductases/dehydrogenases = Oxidoreduction reactions between substrates Transferases = Transfer of a group between substrates Hydrolases = Hydrolysis of various bonds Lyases = Removal of groups from substrates leaving double bonds Isomerases = Catalysis of inter-conversion of isomers Ligases = Joining together of compounds</p> Signup and view all the answers

    Study Notes

    Biomolecules

    • Biomolecules are chemical compounds found in living organisms.
    • They can be classified into two categories: micromolecules (biomolecules) and macromolecules (biomacromolecules).
    • Micromolecules have molecular weights less than 1,000 daltons, while macromolecules have molecular weights above 10,000 daltons.

    Chemical Composition of Living Tissues

    • Water is the most abundant chemical in living organisms, making up 70-90% of the total cellular mass.
    • Proteins make up 10-15% of the total cellular mass.
    • Carbohydrates make up 3% of the total cellular mass.
    • Lipids make up 2% of the total cellular mass.
    • Nucleic acids make up 5-7% of the total cellular mass.
    • Ions make up 1% of the total cellular mass.

    Primary and Secondary Metabolites

    • Primary metabolites are biomolecules that have identifiable functions and play known roles in normal physiological processes.
    • Examples of primary metabolites include amino acids, sugars, and fatty acids.
    • Secondary metabolites are biomolecules that do not have identifiable functions and roles in normal physiological processes.
    • Examples of secondary metabolites include alkaloids, flavonoids, and antibiotics.

    Biomacromolecules

    • Biomacromolecules are large molecules that are found in the acid-insoluble fraction of living tissues.
    • They include proteins, nucleic acids, polysaccharides, and lipids.
    • Lipids are not strictly macromolecules, but are present in the acid-insoluble fraction due to their arrangement in structures like cell membranes.

    Proteins

    • Proteins are polypeptides, which are linear chains of amino acids linked by peptide bonds.
    • There are 20 types of amino acids, making proteins heteropolymers.
    • Proteins carry out many functions in living organisms, including:
      • Transporting nutrients across cell membranes
      • Fighting infectious organisms
      • Acting as hormones
      • Acting as enzymes
      • Sensory reception

    Polysaccharides

    • Polysaccharides are long chains of sugars.

    • They are found in the acid-insoluble fraction of living tissues.

    • Examples of polysaccharides include:

      • Cellulose (a homopolymer of glucose)
      • Starch (a variant of cellulose found in plant tissues)
      • Glycogen (a variant of starch found in animal tissues)
      • Inulin (a polymer of fructose)

    • Polysaccharides can have branches and can form helical secondary structures.

    • Starch can hold I2 molecules in its helical portion, giving it a blue color.### Biomolecules

    • Biomolecules are the building blocks of life, and they are classified into four main categories: carbohydrates, proteins, nucleic acids, and lipids.

    Carbohydrates

    • Cellulose is a complex polysaccharide found in plant cell walls.
    • Chitin is a complex polysaccharide found in the exoskeletons of arthropods.
    • Glycogen is a complex polysaccharide composed of glucose molecules, and its structure is illustrated in Figure 9.2.

    Nucleic Acids

    • Nucleic acids are polynucleotides composed of three chemically distinct components: a heterocyclic compound, a monosaccharide, and a phosphoric acid or phosphate.
    • The heterocyclic compounds in nucleic acids are the nitrogenous bases: adenine, guanine, uracil, cytosine, and thymine.
    • The sugar found in polynucleotides is either ribose (a monosaccharide pentose) or 2’ deoxyribose.
    • Deoxyribonucleic acid (DNA) contains deoxyribose, while ribonucleic acid (RNA) contains ribose.

    Proteins

    • Proteins are heteropolymers containing strings of amino acids.
    • The structure of proteins can be described at four levels: primary, secondary, tertiary, and quaternary.
    • The primary structure of a protein refers to the sequence of amino acids.
    • The secondary structure of a protein refers to the arrangement of amino acids in a helix or sheet.
    • The tertiary structure of a protein refers to the three-dimensional arrangement of the polypeptide chain.
    • The quaternary structure of a protein refers to the arrangement of multiple polypeptide chains (subunits) in a protein.

    Enzymes

    • Enzymes are proteins that catalyze specific chemical reactions.
    • Enzymes have a primary structure, secondary structure, tertiary structure, and quaternary structure.
    • The active site of an enzyme is a crevice or pocket that binds the substrate.
    • Enzymes speed up chemical reactions by reducing the activation energy required.
    • Enzymes are highly specific, and their activity is affected by temperature, pH, substrate concentration, and inhibitors.

    Chemical Reactions

    • Chemical reactions involve the breaking and forming of chemical bonds.
    • The rate of a chemical reaction is the amount of product formed per unit time.
    • Enzymes increase the rate of chemical reactions by catalyzing them.

    Metabolic Pathways

    • A metabolic pathway is a series of enzyme-catalyzed reactions that convert a substrate into a product.
    • Metabolic pathways can lead to different end products depending on the conditions.

    Enzyme Action

    • The enzyme-substrate complex (ES) is formed when the substrate binds to the active site of the enzyme.
    • The ES complex is short-lived and dissociates into the product and the unchanged enzyme.
    • The catalytic cycle of an enzyme involves the binding of the substrate, the formation of the ES complex, and the release of the product.

    Factors Affecting Enzyme Activity

    • Enzyme activity is affected by temperature, pH, substrate concentration, and inhibitors.
    • Each enzyme has an optimal temperature and pH at which it shows maximum activity.
    • Enzyme activity is inhibited by competitive inhibitors, which bind to the active site and prevent the substrate from binding.

    Classification and Nomenclature of Enzymes

    • Enzymes are classified into six classes based on the type of reactions they catalyze.

    • Each enzyme is given a unique four-digit number to identify it.### Enzymes Classification

    • Transferases: catalyze the transfer of a group (G) between two substrates (S and S')

    • Hydrolases: catalyze the hydrolysis of various bonds (ester, ether, peptide, glycosidic, C-C, C-halide, or P-N)

    • Lyases: catalyze the removal of groups from substrates, leaving double bonds

    • Isomerases: catalyze the inter-conversion of optical, geometric, or positional isomers

    • Ligases: catalyze the linking of two compounds, forming bonds (C-O, C-S, C-N, P-O, etc.)

    Co-factors

    • Enzymes are composed of polypeptide chains, but may require non-protein constituents (co-factors) to be catalytically active
    • Co-factors are bound to the apoenzyme (protein portion of the enzyme)
    • Three types of co-factors: prosthetic groups, co-enzymes, and metal ions

    Prosthetic Groups

    • Organic compounds tightly bound to the apoenzyme
    • Example: haem in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide

    Co-enzymes

    • Organic compounds with transient association with the apoenzyme
    • Serve as co-factors in multiple enzyme-catalyzed reactions
    • Often contain vitamins (e.g., NAD and NADP contain niacin)

    Metal Ions

    • Form coordination bonds with side chains at the active site and with the substrate
    • Example: zinc is a co-factor for the proteolytic enzyme carboxypeptidase

    Importance of Co-factors

    • Catalytic activity is lost when the co-factor is removed from the enzyme
    • Co-factors play a crucial role in the catalytic activity of the enzyme

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