Question | Answer |
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 |