Exam 2 Study Guide Flashcards
Explain the rationale of fluorescence microscopy
Some molecules can absorb light at one wavelength and emit light at another wavelength. Fluorescence microscopy is used to see specific structures in a specimen.
compare and contrast TEM and SEM
TEM: electrons pass through ultra thin sections of a specimen; internal structures can be seen
SEM: electrons SCAN the surface of an entire specimen; external structures and topography can be seen
Explain the differences between eukaryotes and prokaryotes
Eukaryotes have a nucleus where all genetic information is stored meanwhile prokaryotes don’t. Eukaryotic cells are also larger, have multiple linear chromosomes, divide by mitosis, have organelles, etc. Prokaryotes divide by binary fission, have singular circle-shaped chromosomes, no organelles, etc.
List common features that are found in all bacterial cells and those found in some
bacterial cells
ALL:
- cell wall (peptidoglycan)
- unicellular
-no membrane-bound organelles
-plasma membrane
SOME:
-capsule
- inclusions such as fimbriae, flagella or plasmids
-spore formation
Describe the structure of the cytoplasmic membrane
Think of phospholipid bilayer
Explain how molecules can move across the membrane, via active or passive mechanisms
Active transport: molecules move from LOW concentration to HIGH concentration; requires energy (ATP) and a transporter protein
Passive: molecules move from HIGH conc. to LOW conc.; does not require energy, 2 types (simple diffusion and facilitated diffusion; facilitated: ions and large molecules pass through a transporter protein)
Describe the structure and function of ribosomes
Structure: made of protein and rRNA (50S + 30S= 70S); synthesizes proteins (translation)
compare and contrast between chromosomes and plasmids
Both: contain genetic information
Plasmid: extra genetic material ( nonessential genes like antibiotic resistance)
Chromosome: makes up the entirety of DNA in eukaryotes
Identify the components of peptidoglycan and describe its structure
chains of alternating sugar residues, NAG, and NAM
peptidoglycan is made up of chains of sugar residues linked together by polypeptide bridges
describe the structure of the cell wall of a Gram pos. bacteria and a Gram neg. bacteria
Gram pos- thick cell wall
gram neg- thin cell wall
identify differences in cell wall structure between GP bacteria and GN bacteria
GP bacteria have thicker cell walls so the initial dye can penetrate the wall and remain there after decolorization. GP bacteria cell walls are held together by teichoic acid and is anchored to the entire membrane by lipoteichoic acid facing the environment. Meanwhile, GN bacteria have thin cell walls that cannot retain the dye after it is decolorized. GN cells layers of peptidoglycan are contained w/in the periplasm (space between cell membrane and outer membrane). They also have porins that allow the entry/exit of molecules. Lastly, GN bacteria are composed of lipopolysaccharides found on the outer membranes leaflet.
Provide a molecular explanation for why the Gram stain isn’t used to stain acid-fast bacteria such as Mycobacterium spp.
Because acid-fast bacterial species have a waxy outer layer, the stains used for a Gram stain will not hold.
Explain HOW and WHY the bacterial cell wall is targeted by components of our immune system and antimicrobial drugs
Since the bacterial cell wall is integral for survival, it also makes it the Achilles heel of bacteria. Lysozymes and beta-lactam antibiotics found in the body attack bacteria in different ways.
Describe the glycocalyx and give examples
The glycocalyx is a general term for the substance external to the cell wall. For example, the capsule of a virus or a slime layer.
Describe the structure of the flagella and how it aids in bacterial motility
The flagella is composed of proteins and allows for motility via rotation and a molecular motor.
Describe the role of fimbriae and pili
Fimbriae and pili are features mostly used for attachment. For fimbriae they are mainly used for biofilm formation and colonization w/in a host. Pili are mainly involved with motility but a conjugation pilus may be used to transfer DNA from one cell to another.
Explain the purpose of endospores
Endospores are resting bacterial cells that are produced when nutrients are depleted. Because endospores are resistant to desiccation, heat, chemicals, and radiation, they make for the perfect shield to protect bacteria.
Explain the role of prokaryotes in the evolution of mitochondria and chloroplasts
Endosymbiotic theory: larger microbial cells engulfed smaller bacterial cells that formed into the first eukaryotes.
Ingested photosynthetic bacteria= chloroplasts
aerobic bacteria: mitochondria
Define metabolism and distinguish between catabolism and anabolism
Metabolism: all chemical reactions w/in an organism
Catabolism: release energy (breaking down molecules)
Anabolism: require energy (building up of molecules)
Describe the role of ATP and enzymes in metabolism
ATP provides energy for reactions that require it. Enzymes catalyze (speed up) reactions.
explain how enzymes convert substrates into products
Enzymes have active sites that are developed during protein folding. The active sites are specific to a certain substrate. The substrate binds to the active site and becomes a product
explain why enzymes exhibit specificity
Enzymes exhibit specificity because of their unique active sites that are formed during protein folding.
Explain how temperature impacts microbial growth on the molecular and cellular level
Molecular: heat affects the rate of catalysis
Cellular: too much heat will denature proteins making them nonfunctional
Describe how heat denatures enzymes using proper terminology
Enzymes can be denatured by heat because they are proteins. Since proteins are made up of specific sequences of amino acids held together by hydrogen bonds, the heat will break the weak H bonds and unfold the protein.
explain how an inhibitor affects enzyme activity
If an inhibitor were to bind to an enzyme’s active site, the substrate would no longer be able to bind to the active site.
Distinguish between a competitive inhibitor and an allosteric inhibitor
Competitive: inhibitor binds at the active site preventing the substrate from binding
Allosteric: inhibitor binds the enzymes at another location causing a conformational change and loss of the active site
Explain how oxygen utilization distinguishes between cellular respiration and fermentation
respiration: requires oxygen as electron acceptor
fermentation: does not require oxygen as an electron acceptor
Distinguish between cellular respiration and fermentation based on oxygen utilization
cellular respiration uses oxygen; fermentation does not
Compare and contrast the processes of cellular respiration and fermentation
o Starts with glycolysis?
o Involves the Krebs cycle?
o Involves the electron transport chain?
o Uses an organic molecule as final electron acceptor?
o Energy yield/efficiency
Respiration: starts with glycolysis, then the Krebs cycle, then ETC; does not use an organic molecule; produces more energy per molecule of glucose but energy is produced slower
Fermentation: starts with glycolysis and does not use Krebs or ETC; has organic molecules synthesized w/in the cell as an electron acceptor; less energy per molecule of glucose BUT produces energy faster
List the products commonly produced during fermentation
acid, alcohol, and/or gas
Using the fermentation test as an example, explain how biochemical tests are used to
differentiate between bacteria
Because bacteria use different enzymes, we can differentiate between bacteria using biochemical tests.
Classify bacteria based on their carbon and energy requirements
Chemoautotroph: CO2 as carbon source, chemicals as energy source
Chemoheterotroph: organic compounds for carbon source, chemicals for energy
Photoautotroph: CO2 as carbon source, light as energy
Photoheterotroph: organic compounds for carbon source, chemicals for energy
Explain what is meant by ‘microbial growth’
Microbial growth describes the growth of a microbial population, not an individual.
Classify bacteria based on their temperature requirements
Psychrophiles: cold temps
Mesophiles: moderate temps (such as room temp or body temp)
Thermophiles: hot temps
Classify bacteria based on their pH requirements
Acidophiles: low pH
Neutrophiles: neutral pH
Alkaliphiles: high pH
Explain how external solute concentration impacts the flow of water into/out of a cell
Osmotic pressure occurs when the concentration inside of the cell is different than outside of the cell. In a hypertonic environment, there is a high solute concentration OUTSIDE the cell. In a hypotonic environment, the solute concentration is higher INSIDE the cell.
Describe the optimal environmental condition for a halophile
A high salt environment
Explain why some bacteria require oxygen (O2) while other bacteria cannot tolerate
oxygen
During respiration O2 is the final electron acceptor, however O2 is highly reactive and can damage bacteria
Explain how aerobic bacteria handle reactive oxygen species (ROS)
They use a variety of enzymes to fight off ROS
Classify bacteria based on their oxygen (O2) requirements
Obligate aerobes: require O2 and rely solely on respiration for energy
Facultative aerobes: can grow with or without O2, perform respiration when O2 is present and fermentation when O2 is absent
Anaerobes: unable to use oxygen and most are harmed by it; perform fermentation
Microaerophiles: require O2 concentration lower than air
Define the following terms and use each appropriately
o Media
o Inoculate
o Incubate
o Culture
Media: collection of nutrients used to grow bacteria in lab
In lab today, we used solid media to grow bacteria
Inoculate: the process of transferring microbes onto media
To grow bacteria I needed to inoculate the media first
Incubate: placing inoculated media at an appropriate temp. for growth
After preparing a bacterial streak plate, I put it in an incubator to incubate and grow.
Culture: the practice of growing microbes in lab OR microbes grown in a lab
Today we are going to culture microbes in lab.
I examined a bacterial culture in lab
Explain the purpose of solid media, liquid media
On solid media, you are able to view colonies easily and can be separated easily so that isolated colonies can form
In liquid media, when all cells are shaken in the broth they all experience the same environmental conditions
Explain why agar is added to media
Agar is added to media to solidify it
Distinguish between complex media and defined media
Complex media: used to grow many different kinds of bacteria; chemical composition is not defined
Defined media: used to grow specific bacteria; chemical comp. is defiined
Explain the purpose of selective and differential media
Selective: designed to suppress the growth of certain bacteria while encouraging others
Differential: designed to distinguish bacteria based on observable characteristics when grown on media
Explain the basis of MSA media as an example of selective and differential media
as a selective media: Contains a high conc. of NaCl which inhibits the growth of most bacteria
as differential media: contains mannitol that some Staphylococcus species ferment while others do not
Describe how a streak plate is used to obtain a pure culture
A streak plate is used to obtain a pure culture because it allows for bacteria to be visible enough to isolate a colony aka pure culture
Describe how bacteria reproduce
Bacteria reproduce via binary fission- cell gets bigger, the genome is replicated, and then it splits into two
Describe how bacterial population size increase over time
bacterial populations double each time they reproduce; some bacteria can take less than 20 minutes to reproduce while some can take up to more than 24hrs
bacterial growth curve: identify the 4 stages and explain what is occurring
during each stage
lag phase: bacteria are preparing for growth before reaching the maximum growth rate
log or exponential phase: unconstrained growth
stationary phase: plateau of growth; number of alive cells is the same as dead cells
death phase: cell death outweighs cell division
Explain the concepts behind the following methods for quantifying bacterial numbers
o Direct microscopic count
o Most probable number
o Quantitative plate count
o Turbidity
Direct microscopic count: cells are counted within a specific parameter and then a calculation is done to determine cell count
MPN: used to estimate the amount of microbes in a sample; it is done using three tests to confirm the presence of coliforms and then to determine the MPN
QPC: involves diluting a sample and then placing the diluted sample on a plate and allowing it to grow, then you can count the colonies
Turbidity: quantifies the amount of light scattering due to a large amount of cells being present
Define and distinguish between sterilization, disinfection, and antisepsis
Sterilization: removing/destroying ALL microbial life
Disinfection: destroying HARMFUL microorgs.; usually used on surfaces
Antisepsis: destroying harmful orgs. from living tissue; iodine, alcohol, hydrogen peroxide are antiseptics; safe for skin
Explain the purpose of the following techniques and how each works:
o Autoclave
o Pasteurization
o Filtration
o Radiation
Autoclave: destroys bacteria at very high levels of heat/steam
Pasteurization: reduces # of microbes; put into high temps for a short time so thermoresistant bacteria survive
Filtration: the passage of a substance through a screen-like material; can remove bacteria up to less than 0.22 micrometers and specialized ones can remove microbes as little as 0.01 micrometers
Radiation: causes mutations–after too many some of them will end up lethal; ionizing: penetrates surfaces, high energy
nonionizing: does not penetrate surfaces
Explain how low temperature impacts microbial growth
Low temps impact bacterial growth because for most species, the low temps will slow or even stop the growth of bacteria
Describe how microbial populations decline
Microbial populations decline exponentially. Treatments can be more or less effective due to, # of microbes, environment, time of exposure, and microbial characteristics
Explain how the disk diffusion method is used to determine the effectiveness of
chemical agents
