Microbiology Exam #2

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Microbiology Exam #2
2014-03-11 13:37:25

Microbiology Exam #2
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  1. Catabolism
    Provides energy & building blocks for anabolism
  2. Anabolism
    Uses energy & building blocks to build large molecules
  3. Enzyme
    • Biological catalyst
    • Specific for a chemical rxn; not used up in that rxn
  4. Factors That Affect Enzyme Activity
    • High temps & extreme pH denature proteins
    • Low temps = rxn rate decreases as molecules move too slowly
  5. Effect of Substrate Concentration On Enzyme Activity
    Enzyme activity increases as substrate concentration increases until saturated (all active sites are occupied)
  6. Competitive Inhibition
    Inhibitor binds to active site - competes with substrate
  7. Noncompetitive Inhibition
    Doesn't bind at active site but rather changes the shape of the active site so the substrate cannot bind
  8. Feedback Inhibition
    End product of metabolic pathway inhibit's enzyme's activity near the start of the pathway
  9. Redox Rxns
    Oxidation rxn (removal of electrons) paired with a reduction rxn (gain of electrons)
  10. Aerobic Respiration
    The final electron acceptor in the ETC is molecular oxygen

    • 3 Steps:
    • 1. Glycolysis
    • 2. Krebs Cycle
    • 3. Oxidative Phosphorylation
  11. Anaerobic Respiration
    • Final electron acceptor is not oxygen
    • Yields less energy than aerobic respiration because only part of the Krebs Cycle operates under anaerobic conditions
    • Ex:  fermintation
  12. Glycolysis
    • Oxidation of glucose into 2 pyruvic acid molecules with a net production of 2 ATP & 2 NADH
    • Occurs in the cytoplasm
  13. Krebs Cycle
    • 2 cycles for every molecule of glucose
    • Pyruvic acid is oxidized & decarboxylated (became Acetyl CoA) & brought into the mitochondria to begin the cycle
    • NAD+ is reduced to NADH & FAD is reduced to FADH2
    • Produces some ATP through phosphorylation
  14. Electron Transport Chain
    • Occurs in mitochondria
    • Carrier molecules go through redox rxns & electrons are passed through the chain
    • Carriers from glycolysis & Krebs Cycle donate electrons to ETC
    • The energy of the electrons are used to produce a lot of ATP by oxidative phosphorylation
  15. Fermentation
    • Releases energy from oxidation of organic molecules; does not require oxygen
    • Does not use Krebs Cycle or ETC
    • Uses an organic molecule as the final electron acceptor
  16. Generation Time Importance
    Time required for a cell to divide or a population to double
  17. Serial Dilutions
  18. Growth Phases
    • Lag Phase = Where cells prepare to divide; DNA replication, elongation, etc
    • Log Phase = Maximum growth rate; all cells are dividing
    • Stationary Phase = Equilibrium; growth rate = death rate
    • Death Phase = More cells dying than dividing; death rate > growth rate
  19. Physical Requirements For Growth
    • Temp
    • pH = ideal is 6.5 - 7.5
    • Osmotic Pressure = hypertonic environments, or an increase in salt or sugar, cause plasmolysis (H2O leaves cell)
  20. Chemical Requirements For Growth
    • Carbon = energy source
    • Nitrogen = in amino acids & proteins
    • Sulfur
    • Phosphorous = in DNA, RNA, ATP, & membranes
    • Trace Elements = usually as enzyme cofactors
  21. Direct Methods Of Measuring Microbial Growth
    • Plate Counts = bacteria is diluted & plated on agar
    • Filtration
    • Mos Probable Number = dilute until no more bacteria are found; count positive tubes; compare with a statistical table
    • Direct Microscopic Count
  22. Indirect Methods Of Measuring Microbial Growth
    • Turbidity
    • Metabolic Activity
    • Dry Weight
  23. Obligate Aerobes
    • Requires oxygen
    • Possess enzymes to combat toxic forms of oxygen
  24. Obligate Anaerobes
    • Lack enzymes
    • No growth in oxygen
  25. Facultative Anaerobes
    Have enzymes but can perform anaerobic respiration
  26. Aerotolerant
    Anaerobic respiration & one enzyme, so it tolerates oxygen
  27. Macroaerophile
    Aerobic but prefers lower levels of oxygen to decrease amount of toxic oxygen produced
  28. Organic Growth Factors
    • Organic compounds obtained from the environment
    • Vitamins, amino acids, purines, & pyrimidines
  29. Sterilization Vs. Sanitization
    Sterilization = removing all microbial life

    Sanitization = lowering microbial counts on things to prevent disease transmission
  30. Sepsis
    Refers to microbial contamination
  31. Asepsis
    Absence of significant contamination
  32. Commercial Sterilization
    Killing C. botulinum endospores in cans
  33. Disinfection
    Reducing or inhibiting growth of non-living surfaces
  34. Antisepsis
    Reducing or inhibiting microbes on living tissues
  35. Bacteriocidal Vs. Bacteriostasis
    Bacteriocidal = kills microbes

    Bacteriostasis = inhibits growth but does not kill microbes
  36. Factors Influencing Effectiveness of Antimicrobial Treatment
    • # of Microbes
    • Environment
    • Time of Exposure
    • Microbial Characteristics
  37. Physical Methods Of Microbial Control
    • Heat
    • Moist Heat Sterilization = autoclave
    • Pasteurization
    • Dry Heat Sterilization
    • Filtration
    • Low Temp
    • High Pressure
    • Dessication = prevents metabolism
    • Osmotic Pressure
    • Radiation
  38. Chemical Methods Of Microbial Control
    • Depends on - concentration of disinfectant, organic matter, pH, & time
    • Use-Dilution Test
    • Phenols & Phenolics
    • Halogens
    • Alcohols
    • Heavy Metal
    • Surfactants
  39. Most Resistant To Least Resistant Microbes
    • Prions
    • Endospores of Bacteria
    • Mycobacteria
    • Cysts of Protozoa
    • Vegetative Protozoa
    • Gram-Neg Bacteria
    • Fungi & Fungal Spores
    • Viruses w/o Envelopes
    • Gram-Pos Bacteria
    • Viruses w/ Lipid Envelopes
  40. DNA Base Pairing & Structure
    • Adenine, Thymine, Cytosine, & Guanine are bases in DNA; A pairs with T & C pairs with G
    • Double helix associated with proteins
    • Backbone is deoxyribose phosphate
    • Strands are held together by H bonds between AT & CG
    • Strands are antiparallel - 5' & 3' end
  41. DNA Synthesis
    • 1. Enzymes unwind the parental double helix
    • 2. Proteins stabilize the unwound parental DNA
    • 3. The leading strand is synthesized continuously by DNA polymerase
    • 4. The lagging strand is synthesized discontinuously.  RNA polymerase synthesizes a short RNA primer, which is then extended by DNA polymerase
    • 5. DNA polymerase digests RNA primer & replaces it with DNA
    • 6. DNA ligase joins the discontinuous fragments of the lagging strand
  42. DNA Gyrase
    Relaxes supercoiled DNA
  43. Helicase
    Unwinds (unzips) DNA
  44. DNA Polymerase
    Adds nucleotides to leading & lagging strands to synthesize new DNA
  45. RNA Polymerase
    Makes short RNA primer for Okazaki fragments
  46. DNA Ligase
    Joins Okazaki fragments together of lagging strand
  47. Transcription
    • DNA is transcribed to make RNA
    • Begins when RNA polymerase binds to the promotor sequence
    • Proceeds in the 5' to 3' direction
    • Stops when it reaches the terminator sequence
    • 1. Initiation = binding of RNA polymerase to the promotor sequence
    • 2. Elongation = adding of RNA nucleotides to the transcript
    • 3. Termination = where we reach the terminator sequence & RNA polymerase leaves DNA
  48. Translation
    • mRNA is translated in codons
    • Begins at start codon (AUG) & ends at nonsense codons (UAA, UAG, UGA)
    • 1. Initiation = ribosomal subunits bind at start codon of mRNA
    • 2. Elongation = tRNA brings amino acids & add to the growing polypeptide chain; enters A site; P site has polypeptide; E site is where tRNA exits
    • 3. Termination = stop codon does not code for amino acids, no peptide bond formed & the polypeptide is released
  49. Genetic Code
    • Degenerate
    • 61 sense codons that code for amino acids
    • 3 nonsense codons
    • tRNA carries the complimentary anticodon
  50. Operon
    • Sequence of DNA with genes that are similar or part of a metabolic pathway (they're all related in some fashion)
    • Contains the regulatory control switch for a gene (operator)
  51. Repression
    • Repressor genes are normally off that we switch on
    • Repressor binds to the operation & prevents RNA polymerase from transcribing the gene
  52. Induction
    • Inducible genes are normally off that we switch on
    • Repressor protein always bound
    • Inducer present, binds repressor protein & prevents binding of repressor to DNA allowing transcription to occur
  53. Mutation
    • A change in the genetic material
    • Occurs in the DNA
  54. Types Of Mutations
    • Base Substitution - change in one base
    • Missense Mutation - results in change in the amino acid
    • Nonsense Mutation - results in a nonsense codon; stop codon happens & we get a shortened amino acid chain
    • Frameshift Mutation - insertion or deletion of one or more nucleotide pairs; DNA strand gets longer or shorter which in turn altars what the amino acid sequence is
  55. Transformation
    • Uptake of naked DNA from the environment
    • Bacteria die & the cell wall breaks down releasing DNA & other cell contents
    • Neighboring cells pick up DNA & can incorporate some genes into their own genome
    • Ex:  capsules
  56. Transduction
    • Bacterial DNA is transferred from one cell to another using a virus
    • Phage virus integrates into host genome & is replicated (no lysis)
    • During lytic cycle, viral genome separates taking bacterial genes with it
    • Replicates, lyses cell, infects new cell
    • Ex:  toxins & antibiotic resistance
  57. Conjugation
    • Transfer of DNA using pilus or mating bridge
    • F+ cell has pilus & can pass on gene(s) to F- cell
    • Genes located on plasmid
    • Ex:  antibiotic resistance
  58. Restriction Enzyme
    An enzyme that cuts double-stranded DNA at specific sites between nucleotides
  59. Recombinant DNA
    • A DNA molecule produced by combining DNA from 2 different sources
    • Useful in biotechnology
  60. How Are Clones Identified & Selected
    • Direct selection for the desired gene - only clones that are obtained are clones of the required gene
    • Identification of the clone from a gene library - contains an initial cloning experiment to produce a clone library representing all or most of the genes present in the cell, followed by analysis of the individual clones to identify the correct ones
  61. Vectors
    • A plasmid or virus used in genetic engineering to insert genes into a cell
    • Properties = self-replication & size that allows them to be manipulated outside the cell
  62. PCR
    • Polymerase Chain Reaction
    • Technique by which small samples of DNA can be quickly amplified (increased to quantities that are large enough for analysis)
    • Used for diagnostic tests that detect the presence of infectious agents & to test for Tuberculosis
  63. DNA Fingerprinting
    • Analysis of DNA by electrophoresis of restriction enzyme fragments of the DNA
    • Used to identify bacterial or viral phages
  64. A reaction involving the breakdown of complex molecules is catabolic and releases energy
  65. Energy is stored in ATP through a process called phosphorylation
  66. The final electron acceptor for aerobic respiration is oxygen
  67. The final electron acceptor for fermentation is an organic compound
  68. The series of reactions that produces ATP and completely breaks down glucose is called the Krebs Cycle
  69. The process that involves a series of stepwise reactions and the enzyme ATP synthase is called the Electron Transport Chain
  70. Aerobic respiration can only be used for the breakdown of carbohydrates - False
  71. The temperature at which a microbe has the best rate of growth is called the optimum growth temperature
  72. The pH range at which most bacteria grow is 6.5 - 7.5
  73. Elements necessary for growth because they help with enzyme function are called trace elements
  74. An obligate anaerobe can grow in the presence of oxygen because it has the enzymes necessary to remove toxic forms of oxygen - False
  75. The phase of growth where growth and death are at equilibrium is called stationary phase
  76. Serial dilutions are created for which technique for counting microbial populations? - Plate Counts
  77. The removal or destruction of all life is called sterilization
  78. The time needed to kill all organisms at 100 degrees Celsius is called the thermal death time
  79. Which method of killing microbes is due to coagulation of proteins? - Moist Heat
  80. The mechanism of action for phenolics like Lysol and Triclosan is increasing membrane permeability
  81. Transcription involves the enzyme RNA polymerase which produces RNA
  82. The genetic code is read at triplets of nucleotides called anticodons - False
  83. Translation is the process where proteins are made
  84. A change in the DNA sequence that results in a different amino acid sequence is called a missense mutation
  85. Ionizing radiation causes DNA to break, base substitutions, & formations of highly reactive ions
  86. A repressible gene is transcribed only when the repressor is bound to the operator sequence - False
  87. Plasmids & viral genomes are examples of vectors
  88. A property of a vector is self replication & self preservation
  89. Selecting a clone containing recombinant DNA can involve the use of an antibiotic resistant gene & a gene involved in color change
  90. The first step in cloning a gene is to create sticky ends in DNA using a restriction enzyme