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microbiology jc

microbiology test 2 chapter 4

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



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