Chapter 7 – Microbiology Answers – Flashcards

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Nutrition
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process by which chemical substances (nutrients) are acquired from the environment and used in cellular activities
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Essential nutrients
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Essential nutrients must be provided to an organism; Two categories of essential nutrients: macronutrients, micronutrients (or trace elements)
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Macronutrients
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required in large quantities; play principal roles in cell structure and metabolism Proteins - nitrogen, carbohydrates - carbon
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Micronutrients (or trace elements)
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required in small amounts; involved in enzyme function and maintenance of protein structure; Manganese, zinc, nickel; nutrients
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Organic nutrients
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contain carbon and hydrogen atoms and are usually the products of living things; Methane (CH4), carbohydrates, lipids, proteins, and nucleic acids
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Inorganic nutrients
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atom or molecule that contains a combination of atoms other than carbon and hydrogen; Metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water
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Chemical Analysis of Cell Contents
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70% water; Proteins; 96% of cell is composed of 6 elements: Carbon, Hydrogen, Oxygen, Phosphorous, Sulfur, Nitrogen
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Heterotroph
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must obtain carbon from an organic form made by other living organisms; proteins, carbohydrates, lipids, and nucleic acids
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Autotroph
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uses CO2 (inorganic gas) as its carbon source; not nutritionally dependent on other living things
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Growth factors
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Organic compounds that cannot be synthesized by an organism because they lack the genetic and metabolic mechanisms to synthesize them; Growth factors must be provided as a nutrient; Essential amino acids, vitamins, nucleotides
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Nutritional types
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Main determinants of nutritional type are: Carbon source – heterotroph, autotroph;Energy source -Chemotroph – gain energy from chemical compounds;Phototrophs – gain energy through photosynthesis
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Photoautotrophs
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Oxygenic photosynthesis; Anoxygenic photosynthesis
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Chemoautotrophs
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lithoautotrophs survive totally on inorganic substances; methanogens, a kind of chemoautotroph, produce methane gas under anaerobic conditions
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Chemoheterotrophs
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Aerobic respiration; two categories: saprobes and parasites
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Saprobes
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free-living microorganisms that feed on organic detritus from dead organisms; Opportunistic pathogen; Facultative parasite
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Parasites
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derive nutrients from host; Pathogens; Some are obligate parasites
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Passive Transport
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does not require energy; substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration; Diffusion; Osmosis – diffusion of water; Facilitated diffusion – requires a carrier
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Active Transport
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requires energy and carrier proteins; gradient independent; Active transport; Group translocation – transported molecule chemically altered; Bulk transport – endocytosis, exocytosis, pinocytosis
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Diffusion
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Net Movement of Molecules Down Their Concentration Gradient (Passive Transport)
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Osmosis
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Diffusion of Water (Passive Transport)
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Isotonic solution
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Water concentration is equal inside and outside of the cell, thus rates of diffusion are equal in both directions
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Hypotonic solution
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Net difussion of water is into the cell; Cell membrane: causes cell to swell and may burst if there is no mechanism to remove the water; Cell wall: swells the protoplast and pushes it tightly against the cell wall, preventing the cell from bursting
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Hypertonic solution
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Water difuses out of the cell; Cell membrane: causes it to shrink and become distoreted; cell wall: causes plasmolysis(shrinks the cell membrane away from the wall)
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Facilitated Diffusion
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Requires a carrier(Passive transport)
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Carrier-mediated active transport
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Atoms or molecules are transported into or out of the cell by specialized receptors, driven by ATP or other high energy molecules
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Group translocation
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transported molecule is chemically altered
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Endocytosis
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bringing substances into the cell through a vesicle or phagosome (bulk transport); Phagocytosis, pinocytosis
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Phagocytosis
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ingests substances or cells(bulk transport)
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Pinocytosis
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ingests liquids(bulk transport)
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Niche
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totality of adaptations organisms make to their habitat
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Environmental factors
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Environmental factors affect the function of metabolic enzymes; Factors include: Temperature, Oxygen requirements, pH, Osmotic pressure, Barometric pressure
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3 Cardinal Temperatures
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Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism; Maximum temperature – highest temperature that permits a microbe’s growth and metabolism; Optimum temperature – promotes the fastest rate of growth and metabolism
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3 Temperature adaptation groups
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Psychrophiles, Mesophiles, Thermophiles
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Psychrophiles
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optimum temperature below 15oC; capable of growth at 0oC
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Mesophiles
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optimum temperature 20o-40oC; most human pathogens
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Thermophiles
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optimum temperature greater than 45oC
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Gas requirements
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Oxygen:As oxygen is utilized it is transformed into several toxic products: Singlet oxygen (1O2), superoxide ion (O2-), peroxide (H2O2), and hydroxyl radicals (OH-); Most cells have developed enzymes that neutralize these chemicals: Superoxide dismutase, catalase; If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats; Carbon dioxide: All microbes require some carbon dioxide in their metabolism
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Aerobe
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utilizes oxygen and can detoxify it
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Obligate aerobe
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cannot grow without oxygen
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Facultative anaaerobe
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utilizes oxygen but can also grow in its absence
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Microaeriphilic
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requires only a small amount of oxygen
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Anaerobe
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does not utilize oxygen
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Obligate anaerobe
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lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment
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Aerotolerant anaerobes
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do not utilize oxygen but can survive and grow in its presence
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Capnophile
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grows best at higher CO2 tensions than normally present in the atmosphere
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Neutrophiles
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Majority of microorganisms grow at a pH between 6 and 8
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Acidophiles
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grow at extreme acid pH
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Alkalinophiles
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grow at extreme alkaline pH
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Barophiles
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can survive under extreme pressure and willl rupture if exposed to normal atmospheric pressure
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Symbiotic
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two organisms live together in a close partnership; mutualism, commensalism, parasitism
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Mutualism
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obligatory, dependent; both members benefit
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Commensalism
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commensal member benefits, other member neither harmed nor benefited
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Parasitism
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parasite is dependent and benefits; host is harmed
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Nonsymbiotic
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organisms are free-living; relationships not required for survival
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Synergism
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members cooperate to produce a result that none of them could do alone
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Antagonism
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actions of one organism affect the success or survival of others in the same community (competition), antibiosis
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Normal flora(microbes and humans)
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symbiotic bacteria, fungi, and a few protozoa
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Biofilms
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result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers; Dominate the structure of most natural environments on earth
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Quorum sensing
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Communicate and cooperate in the formation and function of biofilms
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Microbial growthoccurs at two levels:
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growth at a cellular level with increase in size, and increase in population
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Division of bacterial cells occurs mainly through:
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binary fission
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Binary fission
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Parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells
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Generation or doubling time:
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Time required for a complete fission, can vary from minutes to days
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Exponential growth
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Each new fission cycle increases the population by a factor of 2
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Growth curve
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In laboratory studies, populations typically display a predictable pattern over time
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Lag phase
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“flat” period of adjustment, enlargement; little growth
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Exponential growth phase
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a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment
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Stationary phase
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rate of cell growth equals rate of cell death caused by depleted nutrients and O2, excretion of organic acids and pollutants
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Death phase
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As limiting factors intensify, cells die exponentially
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Turbidometry
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method of analyzing population growth; most simple; degree of cloudiness, turbidity, reflects the relative population size
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Enumeration of bacteria
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method of analyzing population growth; Viable colony count; Direct cell count – count all cells present; automated or manual
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