microbiology test 2 chapter 4
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| Prokaryotic cells divide by: | binary fission
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| Why is binary fission a simpler and quicker way to reproduce? | no organelles, asexual, one cell divides into two daughter cells
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| What is the time it takes for a population to double in number called? | generation time
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| When is exponential growth a positive? | great for experiments and to produce medications such as insulin for diabetics
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| When is exponential growth a negative? | food borne pathogens
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| What are the five stages of the growth curve? | lag phase, exponential or log phase, stationary phase, death phase, and phase of prolonged decline
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| At what phase of growth are microbes most sensitive to antibiotics? | exponential or log phase
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| What happens during the lag phase? | the cells are introduced to the environment, the number of cells does not increase, the cells begin synthesizing enzymes required for growth (the cells are in a vegetative state because they are not metabolically inert)
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| What happens during the exponential/log phase? | cells divide at a constant rate and this is when the generation time is measured
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| At which phase of growth do endospores start to form? | the end of the log/exponential phase
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| What happens during the stationary phase? | nutrient levels are too low to sustain growth and the total number of cells remains constant. A few cells are reproducing as the same number are dyeing
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| What happens during the death phase? | total number of viable cells decrease (die) at a constant rate (exponentially but slower)
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| What happens during the phase of prolonged decline? | some fraction may survive. They adapt to tolerate the worsened conditions
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| What does it mean to say that prokaryotes are ubiquitous? | inhabit nearly all environments
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| What are the major conditions that influence growth? | temperature, pH, water availability, atmosphere (levels of oxygen)
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| Optimum growth usually occurs at what temp: | close to the upper end of the range for that species of microbe
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| Psychrophile: | -5o to 15o C (arctic or Antarctic regions)
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| Psychrotroph: | 20o to 30o C (cause food spoilage in refrigerator)
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| Mesophile: | 25o to 45o C (body temp range-pathogens)
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| Thermophiles: | 45o to 70o C (hot)
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| Will refrigeration kill microbes? | no, but will slow them down
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| What range of pH do most bacteria maintain internally? | typically near neutral
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| Neutrophiles: | pH range 5-8 and have a pH optimum near neutral (pH 7) Most microbes are neutrophiles
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| Acidophiles: | grow optimally at a pH below 5.5
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| Alkaliphiles: | grow optimally at a pH above 8.5
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| How does H. pylori survive in the stomach? | it produces urease to split urea into CO2 and ammonia which neutralized the area around it so it can survive the stomach acid
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| When water leaves cells, what happens? | it interferes with normal metabolic processes
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| What do dissolved salts and sugars do to cells? | make water unavailable to the cell, causing cells to slow their growth or die
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| Microbes that tolerate high concentrations of salt: | halotolerant
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| Microbes that require high levels of sodium chloride: | halophiles
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| When organisms us oxygen in aerobic respiration, what harmful derivatives are formed as by-products? | reactive oxygen species (ROS) (hydrogen peroxide and superoxide)
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| What is superoxide dismutase? | an enzyme produced to inactivate superoxide by converting it to oxygen and hydrogen peroxide
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| What is catalase? | an enzyme produced to convert hydrogen peroxide into oxygen and water.
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| Obligate aerobes: | need oxygen for growth, produces superoxide dismutase and catalase
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| Obligate anaerobes: | cannot multiply in the presence of oxygen, does not produce superoxide dismutase and catalase
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| Facultative anaerobes: | grow best in presence of oxygen but can also grow in the absence of oxygen, produces superoxide dismutase and catalase
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| Microaerophilic: | require small amounts of oxygen for growth, produces some superoxide dismutase and catalase
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| Aerotolerant anaerobes: | don’t use oxygen to grow but being in presence of oxygen isn’t going to kill or hinder them, produces superoxide dismutase but not catalase
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| A species grows must rapidly at its ____________ growth temperature: | optimal
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| During which phase of growth does the number of new cells balance the number of declining cells? | stationary phase
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| The optimum temperature of a psychrophile would be higher, lower, or the same as a thermophile? | lower
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| Microorganisms which prefer hot environments (optimum temperature 45o to 70o C) are termed: | thermophiles
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| When bacteria are transferred from one environment to a new growth medium, which phase of growth is first observed? | lag
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| A _________curve is a graphical representation of the change in population size over time. | growth
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| The enzyme ___________ converts hydrogen peroxide formed during aerobic respiration to water and oxygen. | catalase
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| What name is used to describe a microbe that prefers environments that have a pH greater than 7? | alkaliphile
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| Why are species of Staphylococcus halotolerant? | They have evolved to survive in dry, salty environments such as human skin.
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| If the solute concentration is higher outside the cell than inside the cell, water will diffuse out due to osmosis. This will result in: | plasmolysis
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| True or false:In a growth curve, cell numbers increase exponentially during the log phase and decrease exponentially during the death phase | True
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| What is an organism that prefers acid pH (below 7) called? | acidophile
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| What name is given to microbes that prefer environments near or at a pH of 7? | Neutrophile
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| What phase describes the initial phase after bacterial cells are placed into a new environment and are gearing up for cell division, but their numbers have not yet increased? | lag phase
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| With regard to their temperature requirements, medically important microorganisms are typically __________ because they have evolved to thrive in or on the human body.: | mesophile
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| Which term refers to bacteria that require high concentrations of salt? | halophile
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| What is an aerobe that requires oxygen at a concentration less than that in the atmosphere? | microaerophile
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| Removal of all microbes: | sterilization
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| Reduction of the number of microorganisms: | disinfection
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| Something used on inanimate objects to reduce the number of microorganisms: | disinfectant
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| Something used on living tissue to reduce microorganisms: | antiseptics
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| Brief heating to reduce number of spoilage organisms and destroy pathogens but is not a sterilization method: | pasteurization
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| Process of delaying spoilage of foods and other perishable products: | preservation
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| Why is it important to minimize the number of microorganisms in the healthcare setting? | because of the danger of healthcare associated infections
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| Why is it possible to get a healthcare associated infection? | invasive procedures, compromised immune systems, more infectious diseases found there
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| Destruction of Endospores: | will take extreme heat or chemicals to destroy
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| Destruction of Protozoan cysts: | resistant to any disinfectant and excreted in feces, cause diarrheal diseases, easily destroyed by boiling
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| Destruction of Mycobacterium species: | waxy cell wall makes them resistant to many chemicals
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| Destruction of Pseudomonas species: | leaves green sheen over burn wounds, can actually grow in some disinfectants and is resistant to others
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| Destruction of Naked virus: | doesn’t have a lipid envelope which makes it more resistant to disinfectants
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| The time it takes for heat or chemicals to kill a microbial population is dictated in part by: | the number of cells present
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| What will minimize the amount of time necessary to sterilize or disinfect a product? | removing organisms by washing or scrubbing
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| Why is heat treatment one of the most useful methods of microbial control? | because it is reliable, safe, relatively fast and inexpensive, and does not introduce potentially toxic substances into materials.
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| How does moist heat destroy microbes? | by irreversibly denaturing their proteins
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| Examples of moist heat: | boiling, pasteurization, pressurized steam
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| Boiling: | destroys most microorganisms and viruses but endospores can survive
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| Pasteurization: | destroys pathogens, spoilage organisms
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| Autoclave: | used to sterilize using pressurized steam
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| Temp and pressure sterilization typically takes place in an autoclave: | 121oC & 15 psi in 15 minutes
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| What are the signs and symptoms of botulism and how long does it take to begin? | 12-36 hours after eating toxin contaminated food, dizziness, dry mouth, blurred or double vision, abd pain, nausea, vomiting, diarrhea or constipation, progressive paralysis of all voluntary muscles
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| What is the causative agent of botulism? | Clostridium botulinum a gram-positive, spore forming rod that produces a neurotoxin (works on acetylcholine)
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| Pathogenesis of botulism: | due to vegetative cells releasing the toxin, toxin passes through stomach and is absorbed in the small intestine. Can circulate in the bloodstream
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| Treatment and prevention of botulism: | IV anti-toxin, only neutralizes toxin in blood. Affected nerves slowly recover. Can take weeks or months and respiratory support is needed. Prevention: proper canning
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| What is a method of dry heat sterilization that is used on medical waste, animal carcass, and in the lab: | Incineration
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| What type of radiation has enough energy to remove electrons from atoms, thereby destroying DNA and damaging cytoplasmic membranes? | ionizing
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| A sterile object is free of: | all viable microorganisms and viruses
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| ________ is a brief heat treatment to destroy disease-causing organisms in foods and beverages. | Pasteurization
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| Preventing contamination in the microbiology lab requires the stringent practice of: | aseptic technique
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| A concentrated culture will take __________ time to kill than a dilute culture of the same organism. | more
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| When using chemical disinfectants, it is important to realize that temperature and _________ influence microbial death rates significantly. | pH
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| What is a chamber that allows the use of steam under pressure to sterilize materials? | autoclave
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| What destroys microbes by subjecting them to extremes of dry heat, reducing them to ashes? | incineration
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| These infectious proteins are very difficult to destroy: | Prions
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| ________________radiation in the 220 to 300 nanometer range destroys microbes by damaging their DNA. | Ultraviolet
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| Which microbial agent is the most resistant to chemical control methods? | bacterial endospores
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| Paper-thin membrane filters called _____________contain pore sizes so small they will trap microbes from liquids as they pass through. | microfilters
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| Soap generally does not destroy most microbes but it aids in their: | removal
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| Water treatment facilities work to ensure that these are not found in drinking water: | pathogenic microbes
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| High pressure (130,000 psi) is thought to kill microbes by altering: | their cell membranes and proteins
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| When filtering fluids, ________ trap material within thick, porous filtration material such as cellulose fibers.: | depth filters
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| Removing or destroying all microorganisms and viruses from an object renders the object: | sterile
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| __________are chemicals used to decrease the number of microbes on living tissue. | antiseptics
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| Eliminating most or all pathogens in or on a material: | disinfection
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| Moist heat requires __________ exposure times and lower temperatures than dry heat.: | shorter
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| Exposing proteins to high heat may cause protein: | denaturation
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| What kind of radiation can remove electrons from atoms? | ionizing
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| What kind of rays are ionizing radiation and used to sterilize heat-sensitive materials after packaging? | gamma rays and xrays
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| What kind of radiation destroys microbes directly and is used to destroy microbes in air, water and on surfaces? | ultraviolet radiation
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| Ionizing radiation harms cells by destroying ___________and damaging____________. | DNA, cytoplasmic membranes
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| The sum of all the reactions happening in an organism is: | metabolism
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| What two fundamental tasks must cells accomplish to grow? | synthesize new components for repair and reproduction and harvest energy for survival
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| What are the two components of metabolism? | anabolism and catabolism
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| Reactions produce energy from the breakdown of larger molecules is: | catabolism
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| Reactions involved in the synthesis of cell components is called: | anabolism
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| What is the energy currency of the cell? | ATP (adenosine triphosphate)
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| ATP becomes what when it loses a phosphorous? | ADP
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| Exergonic reactions: | give off energy
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| Endergonic reactions: | take energy to make
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| What three things happen in the breakdown of ATP? | a phosphate is removed, ATP becomes ADP, energy is released
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| What is the role of enzymes in metabolism? | speed up reactions
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| How do enzymes catalyze reactions? | lowering activation energy
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| What assist some enzymes (lock and key)? | cofactors
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| What substances are cofactors? | magnesium, zinc, copper, other trace elements
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| What are FAD and NAD? | electron carriers
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| What environmental factors influence enzyme activity? | temp, pH, salt concentration
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| How do non-competitive inhibitors work? | attach to an allosteric site on the enzyme which changes the shape of the active site so a substrate cannot bind
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| How do competitive inhibitors work? | binds to the active site of the enzyme and obstructs it so the substrate cannot bind
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| How do sulfa drugs inhibit the growth of bacteria? | competes for the active site on the enzyme that converts PABA to folic acid. The folic acid is required for the synthesis of DNA and RNA
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| Why do sulfa drugs not harm the human host? | we do not make folic acid in our bodies
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| What are the three subpathways of aerobic cellular respiration? | glycolysis, tricarboxylic acid cycle (TCA), electron transport chain
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| What is the starting product in glycolysis? | glucose
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| What is the ending product of glycolysis? | 2 pyruvate, 2 NADH, 2 ATP
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| What is the starting product in the transition reaction? | 2 pyruvate
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| What is the ending product in the transition reaction? | 2 acetyl CoA, 2 CO2, 2 NADH
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| What is the beginning product of the TCA cycle? | 2 acetyl CoA
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| What is the ending product of the TCA cycle? | 2 ATP, 6 NADH, 4 CO2
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| What is the beginning product of ETC (electron transport chain)? | electron carriers
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| What is the ending product of ETC(electron transport chain)? | 34 ATP and some H2O
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| What is the final electron acceptor and what would happen without it? | O2 and ETC would stop without it.
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| Where does electron transport chain take place? | occurs within the cell membrane of bacteria
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| Where does glycolysis happen? | cytoplasm of bacteria
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| Where does TCA cycle happen? | cytoplasm of bacteria
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| If an organism lacks an electron transport chain or a suitable inorganic terminal electron acceptor is not available, what might it use? | fermentation
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| The TCA cycle completes the _______________of glucose | oxidation
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| Coenzymes are: | organic cofactors
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| When a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what three critical items? | ATP, reducing power, precursor metabolites
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| The process that links the electron transport chain to ATP synthesis is called: | the chemiosmotic theory
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| Most coenzymes are derived from: | vitamins
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