Cell Density – Microbiology Lab Mid Exam
The key terms of Microbiology Lab Mid Exam include, Cell Density.
What is the purpose of a chemostat?
maintain cultures in log phase – correct
maintain cultures in stationary phase
prevent contamination
determine the concentration of cells in a broth culture
Which of these is a techniques for determining the concentration of cells in a broth cuture?
serial dilution and plating
all of these – correct
most probable number
optical density
I counte 67 colonies on a plate made by spreading 100ul of a 10-7 dilution of a culture. What was the original cell density of the culture?
6.7 x 107 CFU/ml
67 x 107 CFU/ml
6.7 x 109 CFU/ml – correct
unable to determine from the information supplied
What does CFU stand for when expressing the concentration of bacteria in a broth culture?
colony forming units – correct
none of these
cell forming units
citizens for unity
Some ATP’s are generated directly in the Krebs cycle.
True – correct
False
In cellular respiration, when carbon-carbon bonds are broken, hydrogens are released and these are stored on co-enzymes like NAD.
True – correct
False
what is chemiosmosis?
using energy to establis a proton gradient across a membrane – correct
the osmosis of chemicals
the movement of water across a membrane
none of these
What is the role of oxygen in aerobic cellular respiration?
it is the terminal electron acceptor – correct
it is to burn carbon
to make water
oxidize NAD
Some bacteria use a molecule other than oxygen at the terminal electron acceptor.
True – correct
False
In what phase of the bacteria growth curve does the number of cells increase exponentially?
none of these
log phase – correct
stationary phase
lag phase
What factor is likely to cause a broth culture to transition from log phase to stationary phase?
running out of physical room
running out of water
all of these
running out of a particular nutrient – correct
What factor is likely to cause a broth culture to transition from stationary phase to death phase?
the accumulation of toxic wastes – correct
to run out of room
running out of energy
to run out of a particular nutrient
What are complex media?
growth media that contain ingredients that are not fully characterized – correct
media whose exact composition is know
media that repress the growth of certain types of bacteria
none of these
What are differential media?
differential media suppress the growth of some bacteria
contain ingredients to encourage the growth of certain types of bacteria
they allow us to distinguish types of bacteria based on an observable biochemical reaction – correct
all of these
What is the objective of streaking for isolation?
determining the concentration of bacteria in a broth culture
identifying a bacterium
preventing contamination
obtaining pure cultures – correct
What is the purpose of a chemostat?
maintain cultures in log phase – correct
maintain cultures in stationary phase
prevent contamination
determine the concentration of cells in a broth culture
Which of these is a techniques for determining the concentration of cells in a broth cuture?
serial dilution and plating
all of these – correct
most probable number
optical density
I counte 67 colonies on a plate made by spreading 100ul of a 10-7 dilution of a culture. What was the original cell denisty of the culture?
6.7 x 107 CFU/ml
67 x 107 CFU/ml
6.7 x 109 CFU/ml – correct
unable to determine from the information supplied
What does CFU stand for when expressing the concentration of bacteria in a broth culture?
colony forming units – correct
none of these
cell forming units
citizens for unity