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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?
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.
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Match the following organic compounds with their classification:
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What is the tertiary structure of a protein?
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What is the quaternary structure of a protein?
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What type of molecules are almost all enzymes?
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Enzymes isolated from thermophilic organisms are stable at high temperatures.
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What are compounds other than primary metabolites called?
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What is the most abundant chemical in living organisms?
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Lipids are strictly considered macromolecules.
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Proteins are linear chains of __________ linked by peptide bonds.
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Match the following nucleotide components:
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What is the term for the temperature and pH at which an enzyme shows its highest activity?
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What is the term used for the maximum velocity of an enzymatic reaction?
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What is the term for inhibition where the inhibitor closely resembles the substrate and competes for the substrate-binding site?
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Enzymes are composed of one or several ______ chains.
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Match the enzyme classification with the type of reactions they catalyze:
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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
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Polysaccharides are long chains of sugars.
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They are found in the acid-insoluble fraction of living tissues.
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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)
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Polysaccharides can have branches and can form helical secondary structures.
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Starch can hold I2 molecules in its helical portion, giving it a blue color.### Biomolecules
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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
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Enzymes are classified into six classes based on the type of reactions they catalyze.
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Each enzyme is given a unique four-digit number to identify it.### Enzymes Classification
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Transferases: catalyze the transfer of a group (G) between two substrates (S and S')
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Hydrolases: catalyze the hydrolysis of various bonds (ester, ether, peptide, glycosidic, C-C, C-halide, or P-N)
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Lyases: catalyze the removal of groups from substrates, leaving double bonds
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Isomerases: catalyze the inter-conversion of optical, geometric, or positional isomers
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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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Description
Learn about the chemical composition and diversity of living organisms, including primary and secondary biomolecules.
