chapter 6 homework
What factors can affect the doubling time of a bacterial cell?
-Temperature -Moisture -pH -Oxygen levels
The generation time of Mycobacterium tuberculosis is _______.
12 hours
during one cycle, the sodium-potassium pump binds and moves.....
3 Na+ and 2 K+
You ingest 20 cells of Salmonella. This bacterium has a doubling time of 30 minutes. After 4 hours, how many of these bacteria would be present in the body (assuming no immune system responses or other biological activities affect its growth)?
5120
After six generations, how many bacteria would have formed from the reproduction of one bacterium?
64
How many generations does it take for a single bacterial cell to become 256?
8
phosphate
A cell is unable to produce ATP and its cell membrane has lost its integrity because of a deficiency of this nutrient
nitrogen
A cell is unable to synthesize proteins and nucleic acids due to a deficiency in this essential nutrient required for their structure
hydrogen
A cell requires this nutrient for pH maintenance and the bonds between DNA strands
sulfur
A cell's proteins are misshapen or unstable because of its lack of the amino acids cysteine and methionine (composed in part by this nutrient)
carbon
A fundamental component of organic molecules consumed by and produced by the cell
what is a biofilm?
A group of bacteria that accumulate in layers and secrete an protective extracellular material
The bacteria causing the foodborne illness appears to have a short generation time. Which of the following would most accurately describe the pattern of population growth?
Exponential
What type of bacteria will grow in the refrigerator, and why is this usually not a concern?
Psychrophiles; very few are pathogenic to humans
The rate of diffusion is affected by which of the following?
Temperature, size of molecules, and steepness of the concentration gradient
When you inoculate a fresh tube of broth medium, it doesn't instantly turn cloudy. Why is this?
There is lag phase before growth occurs at a level that is visible in the broth.
oxygen
This nutrient is a major part of all organic compounds in the cell as well as water, the major component of the cell
Most bacteria reproduce by ________.
binary fission
Most cultured bacteria tend to multiply by ________.
binary fission
what is the source of energy used to power the sodium-potassium pump?
breakdown of ATP
t/f: Both human and bacterial cells divide by mitosis.
false
t/f: Cell division is triggered exclusively when cells attain a threshold mass.
false
t/f: Cells cannot begin a new round of replication until they have completely finished dividing.
false
t/f: DNA helicase is responsible for adding nucleotides to the growing end of the DNA.
false
t/f: During the stationary phase, binary fission stops.
false
t/f: If you measure turbidity using a spectrophotometer during the death phase, the turbidity will be much lower than it was during the exponential phase.
false
Most of the microbiota in the human body are classified as ______.
mesophiles
Simple diffusion is defined as the movement of _______.
molecules from areas of higher concentration to areas of lower concentration
Cells must ________ their DNA prior to cell division.
replicate
The FtsZ protein is needed to form the ________.
septum
Pathogens usually have _____ doubling times.
short
A red blood cell placed in a hypertonic medium will _______.
shrink
passive transport
simple diffusion, facilitated diffusion, osmosis
When sugar is mixed with water, equilibrium is reached when _______.
the dissolved sugar molecules are evenly distributed throughout the solution
The safe temperature ranges for the storage of foods are determined by _______.
the low temperature where microbes stop multiplying and the high temperature where they physically die
t/f: Environmental factors control microbial growth through their influence on enzyme activity.
true
t/f: If the doubling time of a bacterium is short, the x-axis of a population growth curve will have smaller numbers.
true
During binary fission, one bacterial cell becomes _______ cells.
two genetically identical
Osmosis is best defined as the movement of _______.
water molecules across a membrane from an area of high water concentration to an area of lower concentration
What is the effect of heat on a population of bacteria?
Cells begin to die at a temperature slightly above the maximum.
What food product is least likely to contain viable vegetative pathogens?
Chicken cooked to 170°F
Bacteria that grow in oxygenated environments are referred to as ________.
aerobes
Bacteria that thrive in environments with a pH of greater than 7 are classified as ________.
alkalinophiles
Why are biofilms important in infectious disease?
Bacteria in biofilms are often protected from antibiotics.
The RN educates the patient regarding the process of bacterial cell growth. Which of the following terms best describes the process of cell duplication in which a single bacterial cell undergoes chromosomal replication and division, resulting in two daughter cells?
Binary fission
What is the effect of cold on a population of bacteria?
Cells survive but do not divide at temperatures below the minimum.
chemoheterotroph
Converts nutrients from other organisms into energy and uses an organic carbon source (example: protozoa)
The RN prepares to administer IV fluids for the patient. She may anticipate which of the following types of IV solutions to be ordered for intravascular volume replacement?
Isotonic solution (Ringer's lactate)
saprobe
Metabolizes organic matter of dead organisms for energy and uses an organic carbon source (example: fungi)
You leave your potato salad out on the table at the company picnic. When you made it, you unknowingly introduced 100 cells of Salmonella. How much time will it take for the population of Salmonella to reach at least one million if its doubling time is 20 minutes at picnic conditions?
Over 4 hours
chemoautotroph
Uses simple inorganic compounds for energy and carbon dioxide for a carbon source (example: methanogens)
photoheterotroph
Uses sunlight as an energy source and an organic carbon source (example: purple photosynthetic bacteria)
photoautotroph
Uses sunlight as an energy source and carbon dioxide as a carbon source (example: cyanobacteria)
parasite
Utilizes the tissues of a live host and an organic carbon source (example: pathogens)
If conditions are favorable, the generation time of bacteria _______.
can be as short as 30 minutes
active transport
carrier-mediated transport, phagocytosis, pinocytosis
Which descriptors are likely to have applied to the earliest microbes on the planet?
chemoautotrophic and thermophilic
The structure that divides the bacterial cell in two is termed the ________.
cross septum
Once the limiting factors intensify and bacteria are unable to multiply, the growth curve enters which phase?
death
Which of the following is an example of a biofilm commonly found in the human body?
dental plaque
The energy source for contraction of the FtsZ ring during cell division comes from ________.
hydrolysis of GTP
Refrigeration will _____ the doubling time of most pathogens.
increase
a cell immersed in a high salt environment leads to _______ becauses water diffuses _______.
plasmolysis, out of the cell
Which of the following will pass through a cell membrane most easily?
small nonpolar molecules
the sodium-potassium pump functions to pump...
sodium ions out of the cell and potassium ions into the cell
a cell immersed in a low salt environment leads to ______ becauses water diffuses ________.
swelling, into the cell
the environmental factor that influences bacterial growth the most is _______.
temperature
