Microbiology Quiz on Metabolism and Sterilization
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Questions and Answers

Which of the following correctly defines phototrophs?

  • Organisms that rely on inorganic molecules for energy
  • Organisms that obtain energy from organic compounds
  • Organisms that capture energy from sunlight (correct)
  • Organisms that use chemical reactions for energy

    • What type of heat sterilization is achieved through boiling water?

  • Dry heat
  • Chemical sterilization
  • Radiation
  • Moist heat (correct)

    • Which transport process involves movement against a concentration gradient?

  • Active transport (correct)
  • Facilitated diffusion
  • Osmosis
  • Simple diffusion

    • What type of microbe would most likely thrive in high salt environments?

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

    Which major drug target is affected by aminoglycosides?

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

    What is one of the effects of ultraviolet (UV) radiation on microbial cells?

    <p>Distorts DNA</p> Signup and view all the answers

    What indicates the lag phase in microbial growth?

    <p>Adaptation to the environment</p> Signup and view all the answers

    What is the primary role of enzymes in metabolic reactions?

    <p>Lower the activation energy</p> Signup and view all the answers

    What does drug inactivation in antibiotic resistance refer to?

    <p>Chemical alterations preventing drug function</p> Signup and view all the answers

    Which of the following is NOT a characteristic of an ideal antimicrobial drug?

    <p>Broad-spectrum activity</p> Signup and view all the answers

    In which metabolic pathway is oxygen the final electron acceptor?

    <p>Aerobic respiration</p> Signup and view all the answers

    What is the result of glycolysis when starting with one molecule of glucose?

    <p>2 pyruvate, 2 ATP, and 2 NADH</p> Signup and view all the answers

    Which term describes a reaction that releases energy?

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

    What is the primary end-product of lactic acid fermentation?

    <p>Lactic acid</p> Signup and view all the answers

    Which component of the lac operon serves as a repressor when glucose is present and lactose is absent?

    <p>Repressor protein</p> Signup and view all the answers

    During DNA replication, which model of replication suggests that old and new strands of DNA are mixed?

    <p>Dispersive model</p> Signup and view all the answers

    Which type of mutation leads to a change in the reading frame of the genetic code?

    <p>Deletion mutation</p> Signup and view all the answers

    What characterizes the trp operon when tryptophan is absent?

    <p>Inactive repressor allows transcription</p> Signup and view all the answers

    Which of the following processes involves the physical transfer of genetic material through a sex pilus?

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

    Which of the following factors does NOT influence the effectiveness of antimicrobial agents?

    <p>Color of the agent</p> Signup and view all the answers

    Which nucleic acid is characterized by the sugar ribose in its structure?

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

    Study Notes

    Nutritional Types

    • Phototrophs: obtain energy from light
    • Chemotrophs: obtain energy from chemicals
    • Autotrophs: obtain carbon from inorganic sources (ex: CO2)
    • Heterotrophs: obtain carbon from organic sources (ex: sugars, proteins)

    Transport Processes

    • Passive Transport: movement of substances across a membrane without requiring energy
      • Simple Diffusion: movement from high to low concentration
      • Facilitated Diffusion: movement with the help of membrane proteins
      • Osmosis: movement of water across a semipermeable membrane
        • Hypertonic Solution: higher solute concentration outside the cell causing water to move out
        • Hypotonic Solution: lower solute concentration outside the cell causing water to move in
        • Isotonic Solution: equal solute concentration inside and outside the cell, no net movement of water
    • Active Transport: movement of substances across a membrane requiring energy
      • Primary Active Transport: directly uses ATP to move substances
      • Secondary Active Transport: uses the energy of an electrochemical gradient to move substances
      • Group Translocation: chemically modifies the transported substance as it crosses the membrane
    • Bulk Transport: movement of large particles or fluids across a membrane
      • Endocytosis: imports substances into the cell
      • Exocytosis: exports substances out of the cell

    Environmental Factors

    • Temperature:
      • Psychrotrophs: grow best at low temperatures (0-20°C)
      • Mesophiles: grow best at moderate temperatures (20-40°C)
    • pH:
      • Acidophiles: thrive in acidic environments (pH 1-5.5)
      • Neutrophiles: prefer neutral environments (pH 5.5-8)
      • Alkaliphiles: grow best in alkaline environments (pH 8.5-11.5)
    • Osmotic Pressure:
      • Halophiles: require high salt concentrations for growth
        • Obligate Halophiles: require high salt concentrations (ex: Halobacterium)
        • Facultative Halophiles: can tolerate high salt concentrations, but don't require them (ex: Staphylococcus)
    • Oxygen:
      • Obligate Aerobes: require oxygen for growth
      • Obligate Anaerobes: cannot grow in the presence of oxygen
      • Microaerophiles: require low oxygen concentrations
      • Aerotolerant Anaerobes: can tolerate oxygen, but don't require it
      • Facultative Anaerobes: can grow with or without oxygen

    Microbial Growth

    • Binary Fission: a single cell divides to form two identical daughter cells
    • Growth Curve Phases:
      • Lag Phase: cells are adapting to their environment
      • Exponential (Log) Phase: rapid cell division
      • Stationary Phase: growth rate slows as resources become limited
      • Death Phase: cells begin to die off
    • Generation Time: the time required for a population to double in size

    Metabolism

    • Anabolism: building larger molecules from smaller ones (endergonic: requires energy)
      • Condensation/Dehydration Reactions: release water molecules
    • Catabolism: breaking down larger molecules into smaller ones (exergonic: releases energy)
      • Hydrolytic/Degradation Reactions: use water to break bonds

    Enzymes

    • Biological catalysts that increase the rate of reactions
    • Characteristics:
      • Lower activation energy
      • Specific to their substrates
      • Can be reused
    • Simple Enzyme: consists only of protein
    • Holoenzyme: consists of a protein (apoenzyme) and a non-protein component (cofactor)
      • Cofactors:
        • Metal Ions: ex: Mg2+, Fe2+
        • Coenzymes: organic molecules, often derived from vitamins, ex: NAD+, FAD
    • Active Site: region on an enzyme where the substrate binds

    Factors that Influence Enzyme Activity

    • Temperature: optimal temperature where the enzyme works best
    • pH: optimal pH range for enzyme function
    • Substrate Concentration: increasing substrate concentration increases enzyme activity until saturation is reached
    • Inhibitors and Activators:
      • Competitive Inhibitors: bind to the active site and block substrate access
      • Noncompetitive Inhibitors: bind to a different site on the enzyme, altering its shape and reducing activity
      • Allosteric Inhibitors/Activators: bind to a regulatory site and affect enzyme activity
    • Feedback Inhibition: the end product of a metabolic pathway inhibits an enzyme early in the pathway, regulating the pathway's activity

    Cell Energetics

    • Endergonic Reactions: require energy input
    • Exergonic Reactions: release energy
    • ATP (Adenosine Triphosphate): the universal energy currency of cells

    Oxidation and Reduction

    • OIL RIG: Oxidation Is Loss of electrons, Reduction Is Gain of electrons
    • Electron Carriers: molecules that accept and donate electrons, ex:
      • NAD+/NADH: nicotinamide adenine dinucleotide
      • FAD/FADH2: flavin adenine dinucleotide

    Pathways of Bioenergetics

    • 1. Aerobic Respiration:*
    • Glycolysis:
      • Breaks down glucose into pyruvate
      • Occurs in the cytoplasm
      • Produces 2 ATP and 2 NADH
      • Summary: Glucose → 2 Pyruvate + 2 ATP + 2 NADH
    • Pyruvate Oxidation:
      • Converts pyruvate into acetyl-CoA
      • Occurs in the mitochondrial matrix (in eukaryotes) or cytoplasm (in prokaryotes)
      • Produces 2 NADH
      • Summary: 2 Pyruvate → 2 Acetyl-CoA + 2 NADH
    • Krebs Cycle (Citric Acid Cycle):
      • Oxidizes acetyl-CoA to carbon dioxide
      • Occurs in the mitochondrial matrix (in eukaryotes) or cytoplasm (in prokaryotes)
      • Produces 2 ATP, 6 NADH, and 2 FADH2
      • Summary: 2 Acetyl-CoA → 2 ATP + 6 NADH + 2 FADH2
    • Electron Transport Chain (ETC):
      • A series of electron carriers that transfer electrons
      • Occurs in the inner mitochondrial membrane (in eukaryotes) or the plasma membrane (in prokaryotes)
      • Protons (H+) are pumped across the membrane, creating a proton gradient
    • ATP Synthase:
      • Uses the proton gradient to generate ATP
    • Final Electron Acceptor: Oxygen
    • ATP yield: 38 ATP per glucose
    • Overall Summary: Glucose + 6 O2 + 38 ADP + 38 Pi → 6 CO2 + 6 H2O + 38 ATP
    • 2. Anaerobic Respiration:*
    • Similar to aerobic respiration, but uses a final electron acceptor other than oxygen (ex: sulfate, nitrate)
    • ATP yield varies depending on the final electron acceptor
    • 3. Fermentation:*
    • Uses glycolysis to produce ATP
    • Does not require oxygen
    • Final electron acceptor is an organic molecule (ex: pyruvate, acetaldehyde)
    • Produces various end products (ex: lactic acid, ethanol, gases, acids)
    • ATP yield: 2 ATP per glucose

    Genomes

    • Prokaryotes: single, circular chromosome; located in the nucleoid region
    • Eukaryotes: multiple, linear chromosomes contained within the nucleus
    • Viruses: genome can be composed of DNA or RNA, single or double-stranded

    DNA vs. RNA

    • Nucleic Acids: complex organic molecules that store and transmit genetic information
    • Differences:
      • Sugar: DNA - deoxyribose, RNA - ribose
      • Nitrogenous Bases:
        • DNA - adenine (A), guanine (G), cytosine (C), thymine (T)
        • RNA - adenine (A), guanine (G), cytosine (C), uracil (U)
      • Structure: DNA - double helix, RNA - single-stranded
    • Nucleotide: consists of a sugar, phosphate group, and a nitrogenous base
    • Nucleoside: consists of a sugar and a nitrogenous base

    DNA Structure

    • Characteristics:
      • Double helix
      • Antiparallel strands (5' to 3' and 3' to 5')
      • Bases paired by hydrogen bonds: A-T (2 bonds) and C-G (3 bonds)

    The Flow of Genetic Information

    • Central Dogma: DNA → RNA → Protein
      • Gene: a segment of DNA that codes for a specific protein
      • Transcription: DNA is copied into RNA
      • Messenger RNA (mRNA): carries the genetic code from DNA to the ribosomes
      • Translation: mRNA is translated into protein
    • Ribosomes: site of protein synthesis

    DNA Replication

    • Characteristics:
      • Semiconservative Model: each new DNA molecule contains one original strand and one new strand
      • DNA Polymerase: enzyme that synthesizes new DNA strands
    • Steps:
      • Initiation: DNA is unwound and primers are attached
      • Elongation: new DNA strands are synthesized
      • Termination: replication is completed

    Transcription

    • Gene: a segment of DNA that codes for a specific protein
    • Characteristics:
      • RNA Polymerase: enzyme that synthesizes RNA
      • Steps:
        • Initiation: RNA polymerase binds to the promoter region of the gene
        • Elongation: RNA is synthesized
        • Termination: RNA polymerase reaches a termination signal

    Translation

    • Codons: three-nucleotide sequences in mRNA that code for specific amino acids
      • Sense Codons: code for amino acids
      • Nonsense Codons (Stop Codons): signal the end of translation
    • Involves:
      • mRNA: carries the genetic code from DNA to the ribosomes
      • tRNA: brings specific amino acids to the ribosomes
      • rRNA: component of ribosomes
    • Genetic Code: the set of rules that dictates which codons correspond to which amino acids

    Operons

    • Inducible Operons: genes are expressed only when needed
      • Lac Operon: involved in the metabolism of lactose
        • Promoter: region where RNA polymerase binds
        • Operator: region where the repressor protein binds
        • Structural Genes: code for proteins involved in lactose metabolism
        • Inducer: (ex: allolactose) binds to the repressor, preventing it from binding to the operator, allowing transcription
    • Repressible Operons: genes are normally expressed unless repressed
      • Trp Operon: involved in the synthesis of tryptophan
        • Corepressor: (ex: tryptophan) binds to the repressor, activating it, preventing the repressor from binding to the operator, preventing transcription

    Mutations

    • Changes in the DNA sequence
    • Types:
      • Substitution (Point Mutation): one base is replaced with another
        • Silent Mutation: no change in amino acid sequence
        • Missense Mutation: change in amino acid sequence
        • Nonsense Mutation: results in a stop codon, leading to a truncated protein
      • Frameshift Mutation: insertion or deletion of one or more bases, shifting the reading frame of the gene
        • Insertion: addition of a base
        • Deletion: removal of a base

    Horizontal Gene Transfer

    • Transfer of genetic material between existing cells
    • Types:
      • Conjugation: transfer of genetic material through direct contact between cells
        • Sex Pilus: structure that connects donor and recipient cells
        • F+ Cell: contains the F factor (fertility factor)
        • F- Cell: lacks the F factor
        • Hfr Cell: F factor is integrated into the bacterial chromosome
      • Transformation: uptake of naked DNA from the environment
        • Griffith's Experiment: experiment that demonstrated bacterial transformation
        • S Strain: virulent (smooth)
        • R Strain: non-virulent (rough)
      • Transduction: transfer of genetic material through bacteriophages (viruses that infect bacteria)

    Decontamination

    • Removal or reduction of microbes
    • Inanimate Objects (Fomites):
      • Sanitization: reduces microbial populations to safe levels
      • Disinfection: eliminates most pathogens
      • Sterilization: eliminates all microbes
    • Living Tissue:
      • Degermation: reduces microbes on living tissue
      • Asepsis: techniques that prevent contamination of a sterile field

    Relative Susceptibilities of Microbes to Antimicrobial Agents

    • Prions: Most resistant
    • Endospores: Highly resistant
    • Naked Viruses: Less resistant
    • Hardy Vegetative Bacteria: Resistant
    • Enveloped Viruses: Less resistant
    • Vegetative Bacteria: More susceptible

    Factors that Influence the Killing Rate by Antimicrobial Agents

    • Length of Exposure: longer exposure = greater effectiveness
    • Number of Microbes/Microbial Load: higher load = more difficult to eliminate
    • Nature of Microbes: some microbes are more resistant than others
    • Mode of Action:
      • Microbicidal: kills microbes
      • Microbistatic: inhibits microbial growth
    • Concentration of Agent: higher concentration = greater effectiveness
    • Temperature of Environment: higher temperature = greater effectiveness
    • Presence of Interfering Material: substances like blood, mucus, and feces can interfere with the effectiveness of antimicrobial agents

    Heat

    • Moist Heat: more effective than dry heat
      • Pasteurization: heating at 72°C for 15 seconds to kill pathogens in milk
      • Boiling Water: heating at 100°C for 10 minutes to kill most vegetative cells
      • Autoclave: heating at 121°C under pressure to sterilize
    • Dry Heat: requires longer exposure times
      • Dry Oven: heating at 160-170°C for 2 hours to sterilize
      • Incineration: burning to ash to sterilize

    Radiation

    • Ionizing Radiation: sterilizes by damaging DNA
      • X-rays and Gamma Rays: highly penetrating
    • Non-ionizing Radiation: disinfects by damaging DNA
      • Ultraviolet (UV) Rays: poorly penetrating, mainly for surface disinfection

    Chemicals

    • Antimicrobial Agents: chemicals that kill or inhibit microbial growth
    • Targets:
      • Cell Wall: interfere with cell wall synthesis (ex: penicillins)
      • Plasma Membrane: disrupt the membrane (ex: polymyxins)
      • Nucleic Acid Synthesis: interfere with DNA or RNA synthesis (ex: fluoroquinolones)
      • Protein Synthesis: interfere with protein synthesis (ex: aminoglycosides, tetracyclines)
      • Protein Function: denature proteins (ex: heavy metals)

    Chemotherapy

    • Use of chemicals to treat disease
    • Antimicrobial Drug: a chemical that kills or inhibits microbial growth
      • Antibiotic: an antimicrobial drug produced by a microbe (ex: penicillin)
        • Natural: produced by microbes
        • Synthetic: made in the laboratory
        • Semisynthetic: modified natural antibiotics
    • Narrow Spectrum: effective against a limited range of microbes
    • Broad Spectrum: effective against a wide range of microbes

    Major Drug Targets

    • Cell Wall: ex: penicillins, cephalosporins
    • Plasma Membrane: ex: polymyxins
    • Nucleic Acids: ex: fluoroquinolones, rifamycins
    • Ribosomes: ex: aminoglycosides, tetracyclines, macrolides
    • Metabolic Pathways: ex: sulfonamides, trimethoprim

    Major Antibacterial Drugs

    • Cell Wall Synthesis Inhibitors:
      • Penicillins: block transpeptidation, the final step in peptidoglycan synthesis
      • Miscellaneous: vancomycin, bacitracin
    • Plasma Membrane Disruptors:
      • Polypeptides: disrupt membrane integrity (ex: polymyxins)
    • Nucleic Acid Synthesis Inhibitors:
      • Fluoroquinolones: interfere with DNA gyrase, an enzyme involved in DNA supercoiling
      • Rifamycins: inhibit RNA polymerase, blocking transcription
    • Protein Synthesis Inhibitors:
      • Aminoglycosides: bind to the 30S ribosomal subunit, causing misreading of mRNA
      • Tetracyclines: bind to the 30S ribosomal subunit, blocking tRNA binding
      • Macrolides: bind to the 50S ribosomal subunit, blocking peptide bond formation
    • Folic Acid Synthesis Inhibitors:
      • Sulfamethoxazole: inhibits dihydropteroate synthase, an enzyme involved in folic acid synthesis
      • Trimethoprim: inhibits dihydrofolate reductase, an enzyme involved in folic acid synthesis

    Acquisition of Drug Resistance

    • Mechanism:
      • Gene Transfer:
        • Conjugation: transfer of resistance genes through plasmids
        • Transformation: uptake of resistance genes from the environment
        • Transduction: transfer of resistance genes by bacteriophages
      • Gene Mutations: mutations in genes involved in drug binding or metabolism
    • Consequences:
      • Drug Inactivation: enzymes break down the drug
      • Decreased Permeability: the drug cannot enter the cell
      • Activation of Drug Pumps: the drug is pumped out of the cell
      • Change in Drug Binding Site: the drug cannot bind to its target
      • Use of Alternative Metabolic Pathway: the cell bypasses the pathway blocked by the drug

    Interactions Between Drug and Host

    • Organ Toxicity: some drugs can damage organs (ex: liver, kidneys)
    • Allergic Responses: the immune system can react to the drug
    • Alteration of Microbiota: drugs can kill beneficial bacteria, leading to opportunistic infections

    The Process of Selecting an Antimicrobial Drug

    • 1. Identifying the Microbe: cultures are obtained and identified
    • 2. Testing for Drug Susceptibility:
      • Kirby-Bauer Test: a disk diffusion test
      • Minimum Inhibitory Concentration (MIC): the lowest concentration of a drug that inhibits growth
    • 3. Patient Factors: age, health status, allergies, and other medications are considered.

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    Description

    Test your knowledge on essential microbiological concepts including phototrophs, heat sterilization, and microbial growth phases. This quiz also covers metabolic pathways, antibiotic resistance, and the lac operon. Perfect for students studying microbiology or related fields!

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