Microbiology Flashcards
Describe three ways in which viruses are cultivated., and which are in vivo and in vitro.
In vivo: laboratory-bred animals and embryonic bird tissues.
In Vitro: cell or tissue culture methods
Discuss why antibiotics are not prescribed for a viral infection
Antibiotics designed to treat bacterial infections have no effect on viruses. It is difficult to find drugs that will affect viruses without damaging host cells
Distinguish between organic and inorganic nutrients
Inorganic: Not carbon and hydrogen. Found in the earth’s crust, bodies of water, and the atmosphere. Metals and thier salts.
Organic: Contain Carbon and hydrogen atoms usually the product of living things. Large polymers
List the nutrients that comprise 96% of the dry weight of a bacterial cell
Carbon Hydrogen Oxygen Nitrogen Phosphorous Sulfur
Define an photoautotroph
Energy source: Sunlight
Carbon Source: CO2
Ex: algae, plants
Define a chemoautotroph
Energy source: Organic compounds
Carbon Source: CO2
Ex: Methanogens
Define a photoheterotroph
Energy source: Sunlight
Carbon source: organic
Ex: “rock-eating” bacteria
Define a chemoheterotroph
Energy source: metabolic conversions of the nutrients from other organisms
Carbon source: organic
Ex: Protozoa, fungi, many bacteria, animals
Define saprobe
Free-living organisisms that feed on organic detritus from dead organisms. Decomposers of plant litter, animal matter, and dead microbes. recycle organic nutrients.
Define parasite
Derive nutrients from the cells and tissues of a living host
Define facultative parasite
able to change whether they grow inside of outside of a living host
Define obligate parasite
unable to grow outside of a living host
Distinguish between minimum, maximum, and optimal temp
Min temp: the lowest temp that permits microbes continues growth and metabolism; below this temp its activities stop.
Max: the highest temp at which growth & metabolism can proceed before proteins are denatured.
Opt: an intermediate between the min and the max that promotes the fastest rate of growth & metabolism
Why can psychrotroph and thermoduric organisims can be problematic in microbial food contamination
grow slowly in the cold but have an optimum temp of 15 and 30 degrees Celcius. S. aureus and L. monocytogenes are able to grow at refrigerator temps and cause food-borne illness
Describe the 4 different terms that describe a microbes growth under various oxygen conditions
Aerobes: can use gaseous oxygen
Facultative Anaerobes: do not require oxygen but use it when it’s present
Anaerobes: lack the metabolism enzymes systems for using O2 in respiration
Obligate anerobes: also lack the enzymes for processing toxic oxygen and die in it’s presence
Explain why microbes need to ‘detoxify’ oxygen
Oxygen can be highly reactive and bad for cells..
Define mutualism
Both members benefit
Define commensalism
One member benefits, other member isn’t harmed
Define parasitism
Parasite benefits; host is harmed
Define synergism
Members cooperate and share nutrients
Define antagonism
Some members are inhibited by others
Define a biofilm and the first 2 steps that lead to biofilm formation
Communities of microbes attached to a surface and each other.
1st: a “pioneer” colonizer intially attaches to a surface
2nd: other microbes then attach to those bacteria or a polymeric sugar or protein substance secreted by the microbial colonizers.
Identify binary fission and the 4 basic steps in the process
Central division of one cell into two.
- Parent cells enlarges
- Duplicates its chromosomes
- Starts to pull its cell envelope together to the center of the cell
- Cell wall eventually forms a complete central septum
Identify generation time/ doubling time in microbes
The time required for a complete fission cycle, from parent cell to 2 daughter cells
Identify a growth curve
a predictable pattern of a bacterial population in a closed system.
- Lag phase
- Exponential growth phase
- Stationary phase
- death phase
Which stage is most susceptible to treatment and why
Exponential growth
Actively growing cells are more vulnerable to conditions that disrupt cell metabolism and binary fission.
Which stage is most likely to spread
A person actively shedding bacteria in the early and middle stages of infection is more likely to spread
Identify metabolism
Pertains to all chemical reactions and physical workings of the cell
Define catabolism
Breaks the bonds of larger molecules into smaller molecules. releases energy
Define anabolism
A building and bond-making process that forms larger macromolecules from smaller ones. Requires energy input
Describe why catabolism and anabolism are linked
Energy is never gained or lost by the cell, just transferred
Describe an enzyme
Simply types of proteins. Comprise amino acids like any proteins but can break and form chemical bonds. Biological catalysts.
Increase the rate of chemical reactions
Describe an active site
The lock to an enzyme
Describe a cofactor
Non-protein molecules attached to an enzyme required for enzyme activity
Describe a coenzyme
organic molecules (often modified vitamins)
Describe a holoenzyme
Enzyme plus cofactor
Describe what it means to state an enzyme as a catalyst
They’re able to lower the energy barrier needed to create a reaction
Define ‘enzyme specificty’
An enzyme is specific; it recognizes one and only one complementary shaped substrate
Why is a denatured enzyme bad for a reaction
Because it can no longer function
Explain the difference between a constitutive enzyme and regulated enzymes
Constitutive enzymes: are central to life and so are generally always around. Must be produced at a constant rate all the time.
Regulated: Some enzymes only need to present when they are needed. They are produced and destroyed at specific times
Explain the difference between competitive and noncompetitive inhibition
Competitive Inhibition: molecular “mimic” occupies the active site, preventing actual substrate from binding.
Noncompetitive: Enzymes have 2 binding sites: the active site and a regulatory site. Molecules bind to the regulatory site, which reduces activity.
Explain the difference between a repressed and induced enzyme gene
Enzyme repression: Genetic apparatus responsible for replacing enzymes is automatically turned ‘off’
Enzyme induction: Enzymes appear (are induced- gene is turned on) only when suitable substrates are present
Identify the metabolic pathway
The forming and breaking of cells to create chemical reactions within the body
Identify oxidation
the loss of electrons
Identify reduction
the gain of electrons
Identify redox
Reactions that are common in the cell and are indispensable to the required energy transformations
Identify carrier electrons in redox reactions
Oxidoreductase: enzymes that remove electrons from one substrate and add them to another
Name the chemical where energy from redox reactions is stored and released
ADP
Identify the 3 main catabolic pathways
- Aerobic Respiration
- Anaerobic Respiration
- Fermentation
Aerobic Respiration Stages
- Glycolysis: breaks down Glucose. Uses 2 ATP. Yields 4 ATP 2 NADH
- The Krebs Cycle: Uses acetyl CoA. Yields 6 NADH 2 FAHD2 and 2 ATP
- ETC: Uses 8 NADH and 2 FADH2. Yields 32 to 34 ATP
Anaerobic Respiration
The same as Aerobic excepts uses an inorganic final electron acceptor produces 2 to 36 ATP
Fermentation
Glycolysis same as Aerobic uses organic final electron acceptor. Produces 2 ATP
Describe Oxidative Phosphorylation
the coupling of ATP synthesis to electron transport
Describe what the respiratory chain is
A chain of special redox reactions. Embedded in the inner membrane of the mitochondria. Receives electrons from reduced carries generated and passes them in a sequential and orderly fashion from one redox molecule to the next
How many ATP are produced in total andper NADH/FADH molecule?
NADH gives 3
FADH2 gives 2
Name the final electron acceptor
Oxygen
Describe how the anaerobic respiration differs from aerobic in terms of final electron acceptors, ATP production, and name at least two different types of electron acceptors
It differs in that it doesn’t use oxygen as a final electron acceptor. So anaerobic respiration can produce less ATP, anywhere from 2 to 36 versus 36-38. It can use Nitrate and Sulfate as a final electron acceptor
List three products of fermentation
Alcoholic beverages: ethanol and CO2
Organic acids: lactic and acetic acid
Solvents: acetone & butanol
Name two molecules that can be used in glycolysis besides glucose
Carbohydrates and fats
Describe what amphibolism means and how it contributes to the overall efficiency of the cell
The ability of a system to integrate catabolic and anabolic pathways to improve cell efficiency
Define genome
The sum total of genetice material of an organism
Identify where the genome is located and what it is composed of (DNA or RNA) in bacteria, eukaryotes and viruses
In chromosomes
It’s composed of DNA
Viruses can be DNA or RNA
Contrast the composition, shape, ploidy, and number of chromosomes in eukaryotes,bacteria, and viruses
Eukaryotes: DNA wound around histone proteins, all covered in protein. DNA covered in chromatin protein. Located in the nucleus, diploid or haploid, linear species, 3 dozens/species
Bacteria: DNA condensed into a packet by means of “histone-like proteins”, otherwise naked DNA. 1-3 circular chromosomes, always haploid,
Viruses: Don’t have chromosomes
List the two different types of coding genes
Protein-coding genes & RNA genes
Contrast gene number and density in eukaryotes, bacteria, and viruses
Eukaryotes: 5-100 thousand Large genomes Bacteria: 1-10 thousand Medium genomes Virus: 5-500
Identify phenotype versus genotype
Genotype: the sum of all genotypes; an organisms distinctive genetic makeup
Phenotype: the expression of certain traits
Describe all nucleotides, which are purines/pyrimidines
(A)denine pairs with (T)hymine (G)uanine pairs with (C)ytosine
A and G are purines
T and C are pyrimidines
Double stranded DNA is complementary
How is complementary double strands of DNA are constructed
Replication proceeds in both directions from each starting point
Describe the flow of information in the cell and the central dogma
Replication then transcription and translation
List the three steps of transcription
Initiation
Elongation
Termination
Contrast initiation complexity in eukaryotes and bacteria
- Eukaryotes chromosomes must be exposed
- The second added complexity is that the ‘promoter’ sequence alone is often insufficient to initiate, and distant ‘enhancer’ regions of DNA must also be activated by proteins for transcription in addition to those present at the promoter site
Bacteria chromosomes are already exposed are easier to initiate
Describe the differences in gene organization and processing betweeneukaryotes and bacteria
Bacterial genomes are more compact, and related genes with respect to function can be placed on a single transcript, later separated as different protein genes following translation.
Eukaryotic genes contain introns and exons that must be spliced prior to translation
Describe the differences in ribosomes betweeneukaryotes and bacteria
Ribosomes in bacteria, mitochondria, and chloroplasts are 70S size, made up of 50S and 30S subunits
Eukaryotic ribosomes are 80S, made up of 60S and 40S subunits
Explain what a polyribosome is and why the lack of cellular compartments in bacteria allows for near simultaneous transcription and translation
Many ribosomes on a single transcript are added as the transcript is made.
So many proteins can code at one time
Identify an operon
Protein genes that can be turned on and off as a unit
Contrast gene induction versus repression
Catabolic operons:
Induced by the substrate of the enzyme(s) for which the structural genes code
Only produce the enzyme when the substrate is present
Repressible operons:
Anabolic enzymes
Turned off by the product synthesized by the enzyme
Describe how the lac operon is controlled
Regulator: composed of the gene that codes for a protein capable of repressing the operon (a repressor)
Control locus:
Promoter: recognized by RNA polymerase
Operator: on/off switch
Identify steps in the three processes of genetic exchange: conjugation
Conjugation is a conservative process in which the donor bacterium retains (“conserves”) a copy of the genetic material being transferred
So no bacteria loose or trade DNA, one bacteria makes a copy that will be given to the donor
Compare, contrast, describe, identify steps in the three processes of genetic exchange: transformation
A chromosome released by a lysed cell breaks into fragments small enough to be accepted by a recipient cell
, identify steps in the three processes of genetic exchange: Generalized transduction
Bacteriophage serves as a carrier from a donor cell to a recipient cell
Random fragments of disintegrating host DNA are taken up by the bacteriophage
Virtually any gene from the bacterium can be transmitted
identify F factor
Fertility factor
Contrast F factor versus Hfr conjugation
Plasmid becomes integrated into the F+ donor chromosome
Some chromosomal genes get transferred to the recipient
Plasmid genes may or may not be transferred
Describe what competent bacterial cells are with respect to transformation
Competent: cells that are capable of accepting genetic material
Distinguish between generalized and specialized transduction
In generalized transduction, the bacteriophages can pick up any portion of the host’s genome. In contrast, with specialized transduction, the bacteriophages pick up only specific portions of the host’s DNA
Describe what a transposable element is and how it acts on the genome
“Jumping genes”
Transposable elements capable of shifting from one part of the genome to another
Can be transferred from a chromosome to a plasmid, or vice versa; or from one cell to another in bacteria and some eukaryotes
Some replicate themselves before jumping to the next location and some simply move
Define missense mutation
Any change in the code that leads to the placement of a different amino acid
Define silent mutation
Alters a base, but does notchange the amino acid, and has no effect
Define nonsense mutation
Changes a normal mutation into a stop codon
Define back-mutation
When a gene that has undergonea mutation reverses back to its original basecomposition
Define frameshift mutation
One or more bases are inserted or deleted
Changes the reading frame of the mRNA
Nearly always results in a nonfunctional protein
Define SNP
Single nucleotide polymorphism (SNP) only a single base is altered
