microbio exam 3

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microbio exam 3
2014-07-09 16:23:02
cell metabolism microbial growth control

Cell metabolism
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  1. What is metabolism?  What are the two types and how do they work?
    Metabolism- the sum of all chemical reactions within a living organism

    • TWO kinds
    • Catabolism- the breakdown of complex organic compounds into simpler ones.  Releases Energy/Heat

    Anabolism- the building up of complex organic molecules from simpler ones.  Requires Energy *Releases heat (small amt)
  2. What is activation energy?
    the minimum amount of collision energy required for a chemical reaction
  3. What do you call a substance that speeds up a chemical reaction without being permanently altered?  In living cells, what is the term for this?

    enzymes are biological catalysts

  4. Identify: substrate, holoenzyme, apoenzyme, coenzyme (or cofactor)
    • If the cofactor is an organic molecule, it's called coenzyme.
  5. State what's a protein, and it's activity

    Apoenzyme is ________________
    Cofactor is the _______________
       -Coenzyme is ______________
    Holoenzyme is _________________
    • Apoenzyme- protein, inactive
    • Cofactor - non protein (usually vitamins), activates the apoenzyme
    •     -Coenzyme- same thing as cofactor, only it's organic (contains carbon)
    • Holoenzyme- whole, active enzyme
  6. Names of enzymes usually end in what?  How many classes are they grouped in?
    • "ase"
    • 6 classes, according to type of chemical reaction they catalyze
  7. Name 2 important coenzymes that act as electron carriers in cellular metabolism
    • NADnicotinamide adenine dinucleotide  
    • (aka NADH)
    • FADflavin adenine dinucleotide
    • (aka FADH)
  8. What are three things that influence enzymatic activity?
    • temperature
    • pH
    • substrate concentration
  9. what are the two types of enzyme inhibitors? Define them!
    competitive or non-competitive

    competitive- fill the active site of an enzyme & compete w. the normal substrate

    noncompetitive- interacts with another part of the enzyme (called the allosteric site) which then alters the shape of active site, therefore substrate can no longer bind.
  10. what is feedback inhibition?
    control mechanism that stops the cell from making more substance than what's needed.

    The end product can allosterically inhibit the activity of one of the earlier enzymes in the pathway.
  11. what is oxidation?
    • the removal of electrons
    • often produces energy
  12. what is reduction?
    gaining one or more electrons
  13. oxidation & reduction are always coupled, hence it is called ______?
    redox reaction (short for oxidation-reduction)

    coupled reactions- 1 free energy drives the other.  mechanistically joined
  14. What is ATP?  What "breaks" off to release energy?  What is it called when this group reattaches?
    • adenosine triphosphate, the terminal phosphate group.
    • Phosphate added = phosphorylation.

    ADP + P  =>  ATP
  15. What is cellular respiration?  List it's 3 steps
    An ATP generating process in which molecules are oxidized and the final electron acceptor is an inorganic molecule.

    • 1.Glycolysis
    • 2. Krebs cycle
    • 3. ETS
  16. What is glycolysis?
    the oxidation of glucose to pyruvic acid (with some production of ATP and energy containing NADH)
  17. What is the start product of glycolysis?  What are end results?  Does it require oxygen?
    • Start: glucose
    • End: 2 molecules of pyruvate (or pyruvic acid)
    • - net gain of 2 ATP
    • - generation of 2 NADH carrier molecules

    Does NOT require oxygen
  18. What follows Glycolysis?  What does it do with pyruvate?
    • the Krebs cycle.  
    • Takes pyruvate turns it into Acetyl CoA. *This must happen before it enters the cycle, the process is called decarboxylation (b/c pyruvate must lose a CO2)
  19. What are the end products of the Krebs cycle?

    Where does the Krebs cycle occur in eukaryotes? and prokaryotes?
    CO2, NADH (many), FADH2, & ATP

    • eukaryotes- occurs in outer mitochondrial membrane
    • prokaryotes- plasma membrane- cytoplasm interphase
  20. In the Krebs cycle, for every 2 Acetyl CoA, what is produced?
    2 Acetyl CoA => 4 CO2, 6 NADH, 2 FADH2 

    Along w. 2 ATP generated by substrate-level phosphorylation
  21. What is substrate level phosphorylation?
    ATP is generated when a high-energy Phosphate group is directly transferred from a phosphorylated compound (a substrate) to ADP
  22. What is the Electron Transport System?
    a sequence of carrier molecules that are capable of oxidation & reduction. (they can quickly accept electrons & transfer them in cascade fashion)

    As electrons pass thru the chain, there's a stepwise release of energy, used to drive the chemiosmotic generation of ATP.
  23. Where does the ETS occur in eukaryotes? and prokaryotes?
    ETS occurs in eukaryotes in the INNER membrane of mitochondria

    in prokaryotes it is in the plasma membrane
  24. What is FMN? what is it's role in the ETS?
    FMN - flavin mononucleotide 

    It's capable of performing alternating oxidation & reductions.   It is the first to accept electrons in the ETS and it (the FMN) quickly transfers them to next molecule Coenzyme Q
  25. List steps/order of ETS (in eukaryotes)
    • 1. transfer of e- from NADH to FMN 
    • (results: NADH is oxidized to NADand FMN is reduced to FMNH2)

    • 2.FMNH2 passes 2H+ to other side of membrane & passes 2 e- to Q
    • (results: FMNHis oxidized to FMN & Q picks up additional 2Hfrom surroundings and releases it other side of membrane)

    3. Q transfers electrons to cytochromes (carrier molecules that are proteins AND an iron group), eventually forming H2O.  O2 is the final electron acceptor.

    4.  The extra H+ builds up on one side thus forming an inequality.  The extra H then moves thru ATP synthase (a channel protein).

    5. movement of H+ (protons) thru ATP synthase activates this enzyme to combine ADP + P = ATP.  This is known as chemoiosmotic theory (or the proton motive force)
  26. what is chemiosmosis?
    a mechanism (ETS) that uses a proton gradient across a cytoplasmic membrane to generate ATP
  27. What is a proton gradient?
    the phospholipid membrane is normally impermeable to protons, so when are pumped through, it creates a difference in concentrations of protons on the two sides of a membrane
  28. When is the majority of ATP generated?  (which step)
  29. Every NADH = how much ATP?

    Every FADH2 = how much ATP?
    • NADH yields 3 ATP
    • FADH yields 2 ATP
  30. In bacteria where does ETS occur?
    in plasma membrane
  31. Overall, what are the start and end products of cellular respiration?
    start- sugar/glucose, oxygen, ADP, P

    end- CO2, water, ATP
  32. In cellular respiration, prokaryotes (bacteria) generate how much ATP from 1 molecule of glucose?  Much much do eukaryotes generate from 1 molecule of glucose?
    • Bacteria, 1 glucose= 38 ATP
    • Eukaryotes, 1 glucose= 34 ATP *book says 36

    this is because some energy gets lost when eukaryotes shuttle the electrons across the mitochondrial membranes that separate glycolysis from the ETS chain.  no such separation exists in prokaryotes
  33. What are the physical requirements of microbial growth?
    temperature, pH, osmotic pressure
  34. Microorganisms can be grouped by preferred temperature range.  What does the following mean?
    - pyschrophiles
    - pyschotrophs
    - mesophiles
    - thermophiles
    - hyperthermophiles
    pyschrophiles- cold loving 

    pyschrotrophs- cold loving, associated with food spoilage b/c they grow well in refrigerator temps

    • mesophiles- moderate temp loving
    • thermophiles- heat loving

    hyperthermophiles- extreme heat loving (greater than 80oC, or 176oF)
  35. what does minimum growth temperature mean?
    the lowest temp at which the species will grow

    (Each bacterial species grows at a particular temperature)

    optimal refers to temp that bacteria grows best

    maximum is the highest temp at which growth is possible.
  36. what pH range do bacteria generally grow best in?
    grow best in narrow pH range near neutrality (6.5-7.5)
  37. When bacteria is grown/cultured in a lab, what must be added?
    A buffer.

    (a solution that resists changes in pH when acid or alkali is added to it. Buffers typically involve a weak acid or alkali together with one of its salts)

    as bacteria grows, it's waste products tend to be acidic, chemical buffers are added to neutralize the acids & maintain optimal pH range
  38. What is osmotic pressure?
    the pressure required to prevent movement of water (no solutes) into a solution containing some solutes.

    aka the pressure needed to stop the flow of water across the semipermeable membrane
  39. hypotonic solution equals what for the cell?
    hypotonic= water is a plenty in the solution, therefore it moves INTO the cell.  If cell wall strong it will swell, if weak it will burst (osmotic lysis)
  40. hypertonic solution equals what for the cell?
    hypertonic= less water in solution, therefore it moves OUT OF the cell.  cell & cytoplasm shrinks (plasmolysis)
  41. High osmotic pressure (aka hypertonic to cell) has what effect on cells?
    removes water from cell.  growth of cell becomes limited.

    therefore increasing osmotic pressure can stop growth, a form a preservation esp with foods.
  42. Low osmotic pressure (aka hypotonic to cell) what what effect?
    water will enter the cell, this leads to lysing
  43. What are the chemical requirements for microbial growth?
    sources of carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements (minerals), & organic growth factors
  44. What are obligate anaerobes?
    bacteria that are unable to use oxygen for energy-yielding reactions

    growth occurs only where there is NO OXYGEN they lack enzymes (e.g. superoxide dismutase or catalase) to neutralize harmful forms of oxygen
  45. microbes that are introduced into a culture medium to initiate growth are called ____?

    the microbes that grow & multiply in or on a culture medium are referred to as a culture
  46. what is agar?
    a complex polysaccharide derived from marine alda, used as a solidifying agent in culture mediums
  47. what is chemically defined media?
    a culture medium in which the exact chemical composition is known

    primarily used in lab experimental work
  48. What is complex media?
    exact makeup is unknown.  usually made up of extracts from yeasts, meats, plants, or proteins.
  49. What is selective media?
    designed to suppress growth of unwanted bacteria while encouraging growth of desired bacteria.
  50. What is the streak plate method?
    an isolation method used to get pure cultures, as you spread it further apart, the last streak allows bacteria to grow in isolated colonies (insted of on top of one another)

    works well if what you're trying to isolate is in large #s compared to rest of sample
  51. What are the 4 phases of growth?
    1st - Lag phase: little or no cell ÷, however cells are not dormant, metabolic acitivity is developing

    2nd - Log phase: cells ÷ and grow, cell reproduction is most active here & generation time plateaus (reaches minimum constant)

    3rd - Stationary phase: growth rate slows, # of cell death balances # of new cells.  period of equilibrium

    4th - Death phase: # of deaths exceeds # of new cells being formed.  continues until tiny fraction remains or dies out entirely
  52. What is EMB
    Eosin methylene blue

    Commonly used for the preparation of EMB agar which is a differential medium. It slightly inhibits the growth of Gram-positive bacteria.

    Provides a color indicator marking microbes that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella).

    Organisms that ferment lactose display "nucleated colonies" -- colonies with dark center
  53. What is PEA?
    Phenylethyl Alcohol (PEA) Agar

    selective medium used to inhibit the growth of Gram negative organisms, USED TO PROVE GRAM POS.

    PEA prevents the growth of Gram-negative organisms by disrupting the sturcture of lipids in the Gram-negative membrane.
  54. What is Mannitol salt agar?
    growth mediume. It contains a high concentration of salt. Making it selective for gram + bacterium Staphylococci (since levels of salt is unfavorable to most other bacteria.

    S. aureus produce yellow colonies with yellow zones, whereas other Staph produce small pink or red colonies with no colour change to the medium.
  55. What is sterilization?
    Destruction / removal of all forms of microbial life, including endospores but w/ possible exception of prions

    usually done by steam under pressure or sterilizing gas (eg ethylene oxide)
  56. What is commercial sterilization?
    sufficient heat treatment to kill endospores of C. botulinum in canned food

    more resistant endspores may survive, but will not germinate & grow under normal storage conditions
  57. what is disinfection?
    destruction of vegetative pathogens. chemicals disrupts bacterial walls

    • may make use of physical or chemical methods
    • eg UV radiation, boiling water
  58. What is antisepsis?
    destruction of vegetative pathogens ON LIVING TISSUE (eg human skin)

    chemical is then called an antiseptic
  59. What is degerming?
    removal of microbes from a limited area, such as the skin around an injection site

    mostly mechanical removal by an alcohol-soaked swab
  60. what is sanitization?
    Tx methods utilized to keep microbe levels @ a safe public health levels (eating & drinking utensils)

    eg high temp. washing or dipping into chemical disinfectant
  61. what is an autoclave? how does it function?
    moist heat sterilization.  the units can increase pressure, which = increase temp.
  62. What is pasteurization?
    another method of moist heat sterilization.  mild heating, used on specific foods so has not to permanately damage the food item. eg milk
  63. Name some characteristics of Iodine
    • halogen
    • oldest antiseptic
    • impairs protein synthesis & alters cell membranes

    available as tincture- solution in aqueous alcohol OR iodophor- combo of I and organic molecule when I is released slowly
  64. Types of disinfectants:

    halogens are?  name 2 examples
    effective antimicrobial agents.  eg iodine--> betadine & chlorine--> many varities, fluorine, bromide *not used
  65. Types of disinfectants:

    phenol is what?
    carbolic acid.  very effective but now rarely used due to it's odor & irritates the skin.

    derivatives are phenolics & bisphenols
  66. Name some characteristics of silver?
    • heavy metal
    • is antiseptic
    • exerts antimicrobial activity (referred to as oligodynamic action)
    • Silvadene (topical cream for burns)

    • some other metals w. antispetic qualities:
    • copper
    • zinc
    • gold
    • mercury* no longer used b/c toxic
  67. What are antibiotics?  What does broad spectrum mean?
    • naturally occurring substances that have either bacteriocidal (killing) or bacteriostatic (inhibits growth) properties.
    • many are made from Fungus, particularly streptomyces (more than half of whats used today)

    broad= affects both gram + and - bacteria
  68. What are the different mechanisms that antibiotics work?  And name some examples in each category
    • 1. inhibit cell wall synthesis (particularly peptidoglycan, Gram +).  the cell wall weakens = lysis
    • E.G. Penicillin, ampicillins, vancomycin, they share chemical structure called "B-Lactam ring"

    • 2.inhibits protein synthesis- stops translation, aka protein synthesis.  Effective against Gram + and Gram -
    • E.G. tetracyclines, streptogramins, chlorampenicol

    3. Inhibit Nucleic acid synthesis- common group is - Fluoroquinolones (cipro) interferes with enzymes called gyrases which maintain coiled structure of DNA.

    • 4. Transcription blockers- common group is rifamycins.  They inhibit synthesis of mRNA
    • EG rifampin- used in TB & leprosy  

    5. Inhibits Metabolic Activity- the Sulfonamides (sulfa drugs).  Blocks nucleotide biosynthesis

    6. Injures Plasma Membrane- Polmyxin B, binds to membranes of Gram - (eg Pseudomonas).  Limited to topical use since it also binds eukaryotic cells too