CPA #7 Questions Flashcards
(45 cards)
What is catalase?
an enzyme that coverts hydrogen peroxide to water and molecular oxygen
how do you test for catalase?
add a sample of bacteria to hydrogen peroxide; if it bubbles, catalase is present
what organisms DO NOT have catalase?
obligate anaerobes
why is nitrogen considered a growth-limiting nutrient?
they do not have enough nitrogen to build proteins and nucleotides; anabolisms stops
why are nitrogen fixers critical?
they provide nitrogen in a form that is useable by other organisms; change unusable N2 into usable NH3
define: nitrogen fixation
reduction of nitrogen gas to ammonia
explain the effect of temperature on proteins
if temp. is too high, a protein will denature and lose their shape and function because the hydrogen bonds break
explain the effect of temperature on lipids/phospholipids
if temp. is too low, the membranes of cells will become rigid/fragile; if temp. is too high, lipids can become too fluid and membrane cannot contain the cell/organelle
why are organisms sensitive to pH?
sensitive to changes in acidity; hydrogen ions interfere with hydrogen bonding within proteins and nucleic acids
how does the pH of the vagina and stomach reduce microbial infection?
the acidity of these areas inhibit microbial growth
why is cholera a concern in flooded areas?
Vibrio cholerae (causative agent) grows best outside of the body in water with pH of 9.0
why is water important to microbes? (3 reasons)
- require moist enviro. to be metabolically active
- water is needed to dissolve enzymes and nutrients
- water is a reactant in many metabolic reactions
why is osmotic pressure important?
restricts certain microbes to certain environments
define: obligate halophiles
grow under high osmotic pressure; high salty enviroments; will burst if in freshwater enviro.
define: facultative halophiles
do not require high salt enviro; able to tolerate the salty enviro; Staphylococcus aureus can tolerate up to 20% salt (allows it to colonize on human skin)
what type of relationship do biofilms represent?
complex synergistic (both sides receive greater benefits than if they were by themselves)
where would you find biofilms?
teeth, shower curtains, catheters, mucous membranes of digestive system
what percentage of bacterial diseases do biofilms contribute to?
70%
define: quorum sensing
when microbes respond to the density of nearby microbes; secrete quorum sensing molecules that communicate number and types of cells among the biofilm; how many other like bacteria are around to create a biofilm
minimum number needed to form a biofilm
what is a consequence of quorum sensing?
microbes become more harmful when they are a part of a biofilm; groups of bacteria are more dangerous
define: streak-plate method
an innoculating loop is used to streak a set pattern across a petri dish that gradually dilutes a sample to a point that CFUs are isolated from one another
define: CFU
colony-forming unit
list the 6 types of culture media
defined media, complex media, selective media, differential media, anaerobic media, & transport media
define: defined media
aka synthetic medium; the exact chemical composition is known
