Exam 2 Flashcards
Cytoplasm
The substance inside the plasma membrane
80% water plus carbohydrates, lipids, ions, and proteins (CLIP)
Cytoskeleton in cytoplasm; gives a cell its shape
Which of the following is common to all bacterial species?
Ribosomes, Plasma Membrane
Which of the following is the primary distinction (defining characteristic) between prokaryotic and eukaryotic cells?
Presence vs absence of a nucleus
In bacteria, the ribosomes subunits are:
30S, 50S
A compound that is transported through a membrane by a transporter protein without energy expenditure is called:
Facilitated diffusion
What part of the bacterial cell is targeted by beta-lactam antibiotics?
cell wall
Fluorescent
Some molecules have the ability to absorb light at one wavelength and emit at a different wavelength
These molecules are engineered into bacteria to aid in detection
Fluorescence microscopy: green squiggly lines
What is the defining difference between prokaryotic and eukaryotic cells?
Eukaryotes have a nucleus with DNA, prokaryotes don’t have a nucleus
Which of the following are examples of an anabolic process?
DNA replication, Transcription, Translation
Why: builds DNA, RNA, and protein(s)
Which of the following is found in/at the active site of an enzyme?
Competitive inhibitor, substrate(s), product(s)
Why: products are present at the active site, even if it’s just momentarily
Which of the following is involved in both cellular respiration and fermentation?
Glycolysis
Carbohydrate fermentation tests contain a _________that will change color to signify that fermentation has occurred
pH indicator
Why does enzyme activity decrease as temperature decreases?
Fewer interactions between substrate and enzyme
Which of the following statements most accurately describes the movement of water when a cell is placed in an environment with low solute concentration (e.g. pure water)?
Water diffuses into the cell due to the hypotonic environment, causing the cell to rupture
In the lab, you are inoculating a culture when you:
Transfer some bacteria into media
An experiment began with 5 bacterial cells and ended with 40 cells. How many generations did the cells go through?
3
Why: Start with 5 → 1 double = 10 → 2nd double = 20 (10 x 2) → 3rd double = 40 (20 x 2)
Which of the following statements about oxygen are true?
Oxygen is required by some bacteria (obligate aerobes)
Oxygen is toxic to some bacteria (anaerobes)
Some bacteria use oxygen as the final electron acceptor during cellular respiration
Some bacteria can break down oxygen and reactive oxygen species using enzymes
Which of the following approaches is based on probability/statistics and used for estimating bacterial counts for water safety?
Most Probable Number
Complex Media
Most often used
Supports the growth of many types of bacteria
Contains ingredients like yeast extract, meat extract, and protein digests
Chemical composition of ingredients isn’t defined – so media composition varies slightly from batch to batch
Defined Media
An alternative to complex media
Contains only ingredients whose chemical composition is defined
E.g. glucose, ammonium phosphate, sodium chloride, magnesium sulfate, potassium phosphate
Is more consistent from batch to batch
Only good for growing a certain kind of bacteria
Obligate aerobes
Require oxygen
Rely solely on respiration for energy
Facultative anaerobes
Can grow in the presence or absence of oxygen
Perform respiration when oxygen is present
Perform fermentation (or anaerobic respiration) when oxygen is absent
Anaerobes
Unable to use oxygen and most are harmed by it
Perform fermentation or anaerobic respiration
Microaerophiles
require oxygen concentration lower than air
Psychrophiles
microbes that grow best in cold temperatures
Mesophiles
microbes that grow best in moderate temperatures (including room temp and core body temp)
Thermophiles
microbes that grow best in hot temperatures
Acidophiles
microbes that grow best at low pH
Neutrophiles
microbes that grow best at neutral pH
most bacteria, especially human pathogens, are neutrophiles
human body is a neutral environment; bacteria have evolved to survive in a neutral pH
Metabolism
all chemical reactions within an organism
catalyzed by enzymes (-ase suffix)
Alkaliphiles
microbes that grow best at high pH
Catabolism
Release energy (break down complex molecules)
Ex. Glucose broken down → releases energy (ATP) for bacteria to use
Catabolic processes: Fermentation, respiration
Anabolism
require energy (building of complex molecules)
Energy is often stored in the form of ____
ATP
Lysozyme
Antimicrobial enzyme present in tears and saliva
Breaks the peptide bonds between NAG and NAM residues in peptidoglycan
Part of our innate immune system (kills bacteria non-specifically)
Beta-lactam antibiotics
Inhibits the enzyme (transpeptidase) that forms the peptide bridges in peptidoglycan
Includes penicillin, amoxicillin, etc.
The antibiotics we take allow the bacteria to be targeted
Peptide bridges never get formed → weak cell wall → cell susceptible; will die shortly after
Confocal microscopy
Type of fluorescence microscopy that captures multiple planes to produce a 3-dimensional image
Stack images on top of each other
Multicolored image
Fimbriae
Hairlike appendages (spiky looking) that allow for attachment
Important for biofilm formation, colonization within host
Typically many fimbriae on the cell surface (10’s -100’s)
Composed of the protein pilin that are stacked on top of each other
Pili
Involved in motility (gliding and twitching motility)
Conjugation (sex) pilus: a special type of pilus involved in DNA transfer from one cell to another
Pilus retracts, bringing the two cells in direct contact for DNA exchange
Only one pili per cell
Also composed of the protein pilin
Glycocalyx
General term for substance found external to the cell wall
Sticky and gelatinous layer
Made of polysaccharide (or sometimes polypeptide)
Two types: Capsule and Slime Layer
Capsule (type of glycocalyx)
Common to bacterial pathogens
Protects bacteria from phagocytosis
Phagocytes kill bacteria
Slime layer (type of glycocalyx)
Produced by bacteria in nature
Protects them from their environment; not hiding
Sterilization
Removing/destroying all microbial life
Not practical or necessary in everyday life
Disinfection
Destroying harmful microorganisms
Disinfectants are applied to surfaces (inanimate objects)
Not safe on skin
Practical in everyday life
Ex. Formaldehyde, Bleach, Phenol
Antisepsis
Destroying harmful microorganisms from living tissue
Are mild forms of disinfectants
Can be used on skin
HAI: Hydrogen peroxide, Alcohol, Iodine
Media
Also called growth media or culture media
(singular: medium)
Collection of nutrients used to grow bacteria in the lab
Inoculate (verb)
The process of transferring microbes into media
“I collected some bacteria with a sterile loop and inoculated the media.”
Placing inoculated media at an appropriate temperature for growth (often uses an incubator)
“After inoculating, the media is incubated at 37C overnight.”
Culture
The practice of growing microbes in the lab (verb)
“Today in lab, we cultured E. coli on agar plates.”
Microbes grown in the lab (noun)
“When I arrived in lab, I looked at our culture from the previous class.”
“Today in lab, I inoculated media with E. coli and incubated it to generate a culture.”
Osmotic pressure
results when a solute is at different concentrations inside and outside the cell
Hypertonic environment
higher solute concentration outside the cell
Hypotonic environment
lower solute concentration outside the cell
Isotonic environment
equal concentration inside and outside of cell
Halophile
Microbe that thrives in high salt environment
Even as high as 30% (for comparison, ocean water is ~3%)
Allosteric Inhibition
Inhibitor binds the enzyme at another location, causing a conformational change and loss of the active site
Causes protein to change shape → changes active site shape
Allosteric site: somewhere other than the active site
Strepto
When the cells divide, they multiple next to each other in the same plane
Why it’s a chain
Staphylo
Sarcinae: plane of division changes each time, so it forms a cluster
Active Transport
Substances move from low to high concentration; work against concentration gradient
Requires a transporter protein and energy (ATP)
Cell Wall
Prevents osmotic lysis (cell bursting from osmotic pressure) and protects the cell membrane from environmental stressors
~99% of bacterial cells have a cell wall, but some don’t
Made of peptidoglycan (in bacteria)
Enrichment culture
A selective medium that is used to increase the number of only certain bacteria (to enrich for them)
E.g. a bacterium that is present in small number within a soil or fecal sample
Interested in one type of species in soil sample → use selective media to grow just that species
Turbidity
The cloudiness of a bacterial culture
Is proportional to the number of cells in the culture
Measuring Turbidity
Use a spectrophotometer to quantify turbidity
A beam of light is passed through the bacterial suspension to a light-sensitive detector
Light does or doesn’t get blocked by culture
Live and dead cells block light
Absorbance (or optical density, how much light gets blocked by cells in sample) is measured
Not # of cells and not if they’re dead or alive
Ionizing radiation
X-rays, gamma rays, electron beams
High energy
Ionizes water to form reactive oxygen species (ROS) that wreak havoc
Nonionizing radiation (UV)
Doesn’t penetrate surfaces
Sporulation
endospore formation; process of forming an endospore
Electron Microscopy
Uses electrons instead of photons (light)
The shorter wavelength of electrons gives greater resolution
Used for images too small to be seen with light microscopes, such as viruses
B/W image; impart color after
2 types: TEM + SEM
Germination
Re-activation of endospore to vegetative state
Senses better conditions → reactivates
Transmission (TEM)
Electrons pass through ultrathin sections of a specimen
Internal structures can be seen; image of inside of cell
Scanning (SEM)
Electrons scans the surface of an entire specimen
External structures (ex. cilia) and topography can be seen
Bacteria often use _____________ as their primary energy source
carbohydrates (sugars)
Proteins and lipids are also commonly used as energy sources, but sugars are preferred
Selective media
Designed to suppress the growth of certain bacteria (and encourage the growth of others)
Salts and dyes are often included to inhibit the growth of certain bacteria
E.g. Bismuth sulfite agar is used to select for Salmonella typhi because bismuth sulfite inhibits the growth of most other bacteria
Something is included in the media so that only certain bacteria can grow and others can’t
Radiation causes _________
Mutations (changes in DNA sequence)
After many mutations have accumulated, some (by chance) will have been lethal
Cell not able to reproduce
Lag Phase
Bacterial cells first placed in a new environment; first must ‘prepare’ for growth before reaching a max growth rate
First phase
Before log phase
No increase in population
Log phase (or exponential growth phase)
Period of unconstrained growth
Growth during this phase is exponential
When plotted on a log scale it appears as a straight line with the greatest slope
After lag phase