Microbiology Lab 1232 Exam 2 Study Guide pt 4

jngyen11's version from 2017-04-03 15:56

MLab Ex 19 Environmental Effects on Bacteria Growth Radiation

Section 1

Question Answer
What are the types of radiation mentioned in this labthermonuclear reaction gamma xray
What other type of radiation comprises solar radiationvisible infrared and ultraviolet
What is the order of visible
What is used to sterilize working surfacesUltraviolet or UV radiation
Why is UV radiation effective in destroying most types of microorganismsit alters the DNA of the microorganism by bonding adjacent thymine and cytosine bases on the DNA molecule
Once the adjacent bases on thymine and cytosine have bonded through UV radiation what happens to the cellit is rendered impossible to divide and killing it
The ultraviolet light is usually most lethal to microorganisms at a wavelength of (blank)265 nanometers
The absorption of light by DNA bases is maximal at what wavelength of ultraviolet light265 nanometers

section 2

Question Answer
Define mutationa change in the DNA structure of an organism
Give three alterations in DNAinsertions...deletions...substitutions
Define insertionsone or more bases are inserted into the molecule altering the reading frame
Define deletionsone or more bases are deleted from the molecule again altering the reading frame
Define substitutionsone or more bases are replaced by different bases in the molecule
What are the chromosomal aberrationsthey are more extensive mutations including translocation and inversion
Define translocationwhen a piece of a chromosome detaches from its normal position and becomes joined to a different non-homologous chromosome
Define inversiona piece of a chromosome becomes excised and is then reinserted in the opposite direction into the same chromosome
Protein production can be changed from mutation of the DNA because protein is synthesized off (blank) and RNA is synthesized from (blank)RNA...DNA

Section 3

Question Answer
What is a mutagenagents that can increase the frequency of mutation
In lab 19 what were the two bacteria usedSerratia marcescens and Bacillus subtilis
What is the brick-red pigment associated withSerratia marcescens
Serratia marcescens has a brick-red pigment when grown at (blank) temperature25-30 degrees Celsius
If Serratia marcescens are exposed to UV light the bacterium gives (blank) colonies at 25-30 degrees Celsiuswhite or colorless
If mutated or white S. marcescens is exposed to sunlight a (blank) results meaning the bacterium will once more become enabled to produce the red pigmentback-mutation
What microorganism or family of organisms are the most radiation-resistant vegetative cellsDeinococcus radiodurans
Deinococcus radiodurans' extreme resistance to high levels of ionizing and ultraviolet radiation is thought to be due to (blank)its ability to repair damaged chromosomes

MLab Ex 20

Section 1

Question Answer
All natural systems tend toward a state of (blank)equilibrium
Natural systems will attempt to maintain equilibrium even if environmental conditions (blank)change
To maintain balance the cell membrane of a bacterium or any other living cell can (blank)gain or lose water readily
Osmosis is the (blank)movement of water through a semipermeable membrane
Define solutessubstances dissolved in water
In the absence of other forces water will move across a semipermeable membrane in such a way as to (blank)as to maintain equilibrium by equalizing the solute concentration on both sides of the membrane
Define isotonic environmentthe solute concentration is the same on both sides of the cell membrane therefore there is no net movement of water across the membrane
Define hypotonic environmentthe cell is placed into water that contains few solutes relative to the inside of the cell

Section 2

Question Answer
What happens in a hypotonic environmentwater will rush into the cell as the system attempts to equilibriate the solute concentration on the two sides of the cell membrane
What happens if the environment is very hypotonicthe cell can actually lyse which means rupture due to excessive swelling
Define hypertonic environmentthe concentration of solutes is higher outside the cell than inside it and as a result water wil leave the cell to compensate
What happens if a cell is placed in a hypertonic environmentcells in a hypertonic environment become shriveled and cannot carry out most of their metabolic processes
Why do we add high concentrations of salt or sugar to the foodit creates a hypertonic environment for the microorganisms ? after a long exposure

Section 3

Question Answer
Define halotolerantmicroorganisms that can withstand high concentrations of salt without being significantly inhibited
Give an example of a halotolerant microorganism mentioned in the labStaphylococcus
What can grow in high levels of sugar which are inhibited by some bacteria growthmany fungi
What is an example of a fungi that can grow in the sugar environmentSaccharomyces cerevisiae
Escherichia coli is Gram- (blank) while Streptococcus mutans is Gram- (blank)negative and positive