Exam 2 Flashcards
Walter Sutton was one of the first biologists to clearly propose the idea that:
the hereditary material of a cell resides in its chromosomes
Nicotinamide adenine dinucleotide (NAD) is an important molecule in the overall metabolism of cells because it acts as a(an):
intracellular hydrogen-atom carrier molecule
All of the following enzymes are essential participants in DNA replication at the replication forks in the E. Coli chromosomes except:
RNA polymerase
A chemical compound that slows down an enzyme’s activity, and its effect can be reversed by adding more of the enzyme’s substrate, is called a(an):
competitive inhibitor
In autotrophy, carbon dioxide is reduced to cellular material that is approximately at the oxidation-reduction level of carbohydrates. Given our discussion about heterotrophic metabolism in lecture, what unique problem would these organisms need to solve?
how to obtain extra hydrogen atoms (electrons) for CO2 reduction
Ethylene oxide is most commonly used to sterilize:
plasticware
Filters remove microbes from fluids (liquids and gases) due to:
Two or more are correct
If a microbe (such as yeast) carries out an essentially pure ethanol fermentation through the Emden-Meyerhof pathway with glucose as the carbon and energy source, what is the other required end product in the fermentation?
Carbon Dioxide
Why would CO2 be the required end product?
The breakdown of pyruvic acid to ethanol would necessarily also produce a one-carbon unit that is released as carbon dioxide.
When the chemical composition of dried bacterial cells is determined, the element that will be found in the highest amount is:
Carbon
What type of antimicrobial agent is a quaternary ammonium compound?
Surfactant
Lack of the enzymes superoxide dismutase and catalase in some bacteria may explain:
the inability of a bacterial species to grow in the presence of oxygen
A student finds mold growing on the surface of an orange in his refrigerator at home. Streaks the mold onto PDA plate then leaves the plate on a shelf in the walk-in incubator. Checks the plate and finds no growth. What has gone wrong?
The mold is psychrophilic and does not grow at 37 degrees Celsius.
After a microorganism is shifter from anaerobic to aerobic conditions, the rate of its sugar catabolism decreases dramatically. This phenomenon was first reported by Louis Pasteur and is called the Pasteur effect. Based on discussion about metabolism, what is the best explanation for this observation?
The aerobically growing cells are able to obtain the same amount of ATP from far fewer sugar molecules.
The enzyme that links the Emden-Meyerhof pathway with the citric acid cycle during aerobic respiration uses which of the following compounds as a substrate?
pyruvic acid
What is the mode of action for tetracycline in controlling bacterial infections?
it inhibits protein synthesis
In aerobic respiration, the electron transport chain ______ molecular oxygen (O2) and ______ NADH.
reduces; oxidizes
The doubling (generation) time of a bacterial culture varies with the:
Two or more are correct (temperature and species)
Why do concentrated sugar or salt solutions inhibit microbial growth?
They cause water to flow out of the cell, resulting in shrinkage of the cytoplasm.
A certain bacterium, found in a playa lake, grows anaerobically only in the sunlight and assimilates pyruvic acid from the water as its source of carbon. This organism is best described as a:
photoheterotroph
All of the following methods are effective ways to achieve sterilization except:
boiling
Why is boiling not considered to be a sterilization method?
Boiling (at 100 degrees C) kills vegetative cells but does not destroy endospores.
Doubling (or generation) time refers to:
the amount of time it takes for a bacterial population to double in number
A sequence of enzyme-catalyzed reactions that is organized as a unit to make a required end product is called:
an enzyme pathway
A bacterium produces the following fermentation end products from glucose: ….. The fermentation pattern of this bacterium is best described as a(an):
mixed acid fermentation
The primer in DNA replication is:
and RNA starter sequence with a free 3’-OH group
What is the mode of action for Penicillin G in controlling bacterial infections?
it inhibits cell wall synthesis
Why is penicillin ineffective against fungal infections?
Eukaryotic cell walls do not contain peptidoglycan.
The aerobic electron transport chain of E. Coli contains all of the following biochemical components except:
sterols
The basic role of transfer RNA (tRNA) in translation is to:
deliver the appropriate amino acids to ribosome
Asexual reproduction in yeast usually occurs via the process of:
budding
Halogens kill microbial cells primarily by:
inactivating essential enzymes
What is a sanitizer?
a chemical agent that reduces microbial populations to safe levels as defined by public health standards
Under standardized test conditions, isopropyl alcohol has a phenol coefficient of 0.5 against S. aureus. This means that isopropyl alcohol:
is a less effective disinfectant than phenol against S. aureus
The proton gradient represents a form of stored energy because:
Two or more are correct
What role did Gerhard Domagk play in the history of antimicrobial chemotherapy?
He discovered the first sulfa drug.
The type of metabolism in which the final hydrogen (electron) acceptor used by the cell is always generated by the cell’s endogenous metabolism is called:
fermentation
The number of cells per milliliter in an E. coli culture is 1x10^6 when growth begins. The number of cells per milliliter reaches 2x10^9 at the end of growth. The doubling time of the culture is 30 min. How long is the total period growth?
320 minutes
When the chromosome replicates, how is the newly made strand related to its template strand?
The two strands have complementary sequences and are antiparallel to each other.
Plates of E. coli were irradiated with ultraviolet light to determine the rate of cell killing. No decrease was seen in the number of colonies on the irradiated plates compared to the non-irradiated plates. What mistake did this student make?
He left the lids on the spread plates, and the UV light was unable to penetrate the plastic barrier.
