BIOL 275 Exam 4 Prep Flashcards
(118 cards)
1
Q
What is the goal of metabolism? Explain how it differs in prokaryotes.
A
Growth - because prokaryotes are a unicellular, growth results in an increase in the population number due to binary fission.
2
Q
What do organisms need for growth?
A
Nutrients - commonly carbon, oxygen, nitrogen, and hydrogen
Specific physical requirements:
- Temperature ranges
- pH ranges
- Ability to withstand osmotic pressure
3
Q
What is required for metabolism?
A
Sources of:
- Carbon
- Energy
- Electrons or hydrogen
4
Q
Describe the difference (with examples) between macro and micronutrients.
A
Macronutrients (AKA essential nutrients):
- Carbon
- Oxygen
- Hydrogen
- Nitrogen
- Sulfur
- Phosphorus
Micronutrients (AKA trace elements) - usually metals for enzyme co-factors.
- Potassium
- Calcium
- Magnesium
- Zinc
- Iron
- Copper
- Cobalt
- Nickel
5
Q
How would you group organisms based on their carbon, energy, and electron sources?
A
Carbon source:
- Autotroph (carbon dioxide)
- Heterotroph (organic compounds)
Energy source:
- Phototroph (light)
- Chemotroph (chemical compounds)
Electron source:
- Organotroph (organic molecules)
- Lithotroph (inorganic molecules)
6
Q
Why is it important to understand the importance of oxygen regarding growth and metabolism?
A
Oxygen is required as the final electron accept in aerobic respiration.
- Obligate aerobes require oxygen to survive.
- Obligate anaerobes die in the presence of oxygen.
- Facultative anaerobes prefer oxygen but can survive without it.
- Aerotolerant anaerobes tolerate oxygen through enzymes that detoxify reactive oxygen.
- Microaerophiles require very small amounts of oxygen to survive.
Additionally, oxygen may be toxic in highly reactive forms (Reactive Oxygen Species)
7
Q
What are the types of toxic Reactive Oxygen Species?
A
Singlet oxygen - very reactive oxidizing agent made by aerobic metabolism or light reactions
Superoxide radical - caused by incomplete reduction of oxygen in the ETC (removed by superoxide dismutase). Extremely toxic oxidizing agent.
Peroxide anion - produced by superoxide dismutase (removed by catalase or peroxidase)
Hydroxyl radical - MOST TOXIC oxygen…made by ionizing radiation (UV light) and incomplete reduction of hydrogen peroxide
8
Q
How is toxic oxygen removed/neutralized?
A
Singlet oxygen - boost to higher energy state
Superoxide radicals - superoxide dismutase (makes hydrogen peroxide)
Peroxide anion - catalase (aerobes use…creates water and oxygen) or peroxidase (anaerobes use….makes only water because oxygen kills them)
Hydroxyl radicals - cannot be removed, but low amounts in aerobes due to catalase/peroxidase
(Enzymes that neutralize oxygen are called “antioxidants”)
9
Q
Why is nitrogen important?
A
Required for anabolism (amino acids and nucleotides need it).
Comes from:
- Recycling amino acids/nucleotides
- Ammonia from environment
- Nitrogen fixing bacteria convert nitrogen gas to ammonia
10
Q
Why is phosphorus important? Why is sulfur important?
A
Phosphorus:
- Used in DNA, RNA, ATP, and phospholipid bilayer
Sulfur:
- Some amino acids/vitamins
11
Q
Describe the importance of trace elements. What are growth factors?
A
Trace elements are inorganic elements usually used as enzyme co-factors.
Growth factors are organic elements needed in fastidious organisms (cannot make their own).
- Obtained through environment
- Vitamins, amino acids, purines, pyrimidines
- Can be organic co-factors for enzymes
12
Q
What is generation time?
A
Time needed for a bacterial cell to double itself. Growth is exponential (logarithmic)
Dependent on:
- Chemical conditions
- Physical conditions
13
Q
What is binary fission?
A
Method in which unicellular organisms grow/reproduce. The cell grows twice its normal size and divides in half to produce two daughter cells.
14
Q
What are the phases of microbial growth?
A
- Lag phase - little growth, adjusting to environment, making enzymes
- Log phase - exponential growth, primary metabolite production, most susceptible to antimicrobial drugs
- Stationary phase - equal number growth/death, secondary metabolite production, waste products made
- Death phase - more deaths (exponential rate) than growth
- Phase of prolonged decline - viable cells use dead cells’ nutrients to continue to survive*
15
Q
How would you label the X and Y axis on a growth curve?
A
X-axis - time in hours/minutes
Y-axis - number of cells (log scale)
16
Q
Formulas for: 1.) Number cells in a population? 2.) Number of generations? 3.) Generation time?
A
1.) Number of cells in a population = for one cell: 2^n (n=number of generation)
For more than one cell = original number of cells x 2^n
2.) Number of generations:
( (Log(end number of cells) - (Log(beginning number of cells) ) / 0.301
3.) Generation time (in min/generation):
(60min x Number of hours) / number of generations
17
Q
What is the primary use of a chemostat?
A
Allows you to maintain a constant nutrient level so you can keep bacteria in a certain growth phase
18
Q
What methods can you use for measure microbial growth?
A
Direct methods (actual counting):
- Microscopic counts: view cells under microscope
- Coulter counter: counts cells as they flow through electrical current
- Flow cytometry: counts cells via light transmission
- Viable plate counts: serial dilutions to count CFU/mL (just like in lab 2)
Indirect methods (estimation via characteristics):
- Turbidity: measures cloudiness via light passing through
- Dry weight: microbes filtered, then dried and weighed
19
Q
Catabolism vs. anabolism
A
Catabolism - exergonic, breaking down molecules and releasing energy and heat
Anabolism - endergonic, building complex molecules using energy
20
Q
What carries out metabolism?
A
Usually proteins as enzymes (catalysts):
- Breaks or forms bonds
21
Q
Describe enzyme structure(s):
A
An enzyme may have:
- Apoenzyme: protein portion of an enzyme that requires a cofactor
- Active site: functional site that is specific to a substrate
- Allosteric site: functional site used to activate or inhibit enzyme function
- Cofactor: non-protein chemical that is required for apoenzyme to function (trace metals)
A “holoenzyme” is a complete, functional protein enzyme with its cofactor.
(Cofactors that are vitamins are called coenzymes)
22
Q
What are catalysts? What is an enzyme?
A
Catalysts are molecules that lower the activation energy required to trigger a chemical reaction (therefore speeding the reaction time up).
Enzymes are proteins that are catalysts.
23
Q
Describe how enzymes work
A
The amino acid sequence of the enzyme determines the shape of the active site.
The active site is specific to a substrate and when a substrate and active site bind, this induces a close fit (induced-fit model).
Bonds are then broken or formed, the products are released, and then enzyme returns to its original shape.
24
Q
What are some factors that affect enzyme activity?
A
Temperature - affects protein folding and can completely denature it
pH - hydrogen ions affect hydrogen bonding/protein structure
Enzyme/substrate concentration - increasing # of substrates increases activity until eventually reaching saturation point (no free active sites)
Inhibition/activation - blocks active site or uses allosteric site to change shape of active site
25
Describe the different between the following enzyme types: inducible, repressible, and constitutive.
Inducible: activated or expressed in response to a substrate
Repressible: in-activated in response to substrate
Constitutive: always active/expressed
26
Describe enzyme inhibition and activation
Feedback inhibition - end product of multiple enzyme reactions inhibits the 1st reaction, which shuts down all subsequent reactions
Competitive inhibition - inhibitor blocks the active site
Non-competitive inhibition - inhibitor binds to allosteric site to change shape of active site
Allosteric activation - activator binds to allosteric site to change shape of active site
Cofactor activation - loosely binds to enzyme/substrate to make enzyme functional
27
What are the 6 categories of enzymes?
Hydrolase - catabolic; breaking down using water (process of hydrolysis)
Isomerase - neither catabolic/anabolic; simply rearranges atoms in molecule (ex. DHAP to G3P in glycolysis)
Ligase/polymerase - anabolic; joins 2 molecules together (ex. DNA polymerase)
Lyases - catabolic; splits molecules without water (ex. aldolase splits fructose 1,6-BP into G3P/DHAP in glycolysis)
Oxidoreductase - both catabolic and anabolic; removes or adds electrons to substrates (ex. dehydrogenase removes hydrogen atoms in ETC reactions)
Transferase - anabolic; transfers functional groups between molecules (ex. kinases transfer phosphate groups such as glycolysis)
28
What is a metabolic pathway?
Sequence of enzymatically catalyzed chemical reactions:
- pathway made of up enzymes
- either catabolic or anabolic
Ex. glycolysis (catabolic pathway)
29
What are some characteristics about metabolic processes?
- Every cell acquires nutrients
- Metabolism requires energy
- Energy is stored in phosphate bonds of ATP
- Cells catabolize nutrients using enzymes to make precursor metabolites
- Precursor metabolites, energy, and enzymes are used in anabolic reactions
- Enzymes + ATP form macromolecules (via polymerization)
- Cells grow by turning macromolecules into structures
- Cells reproduce once they've doubled in size
30
What is, and what are the 3 types of phosphorylation?
Phosphorylation is the concentration of energy released from nutrients to phosphate bonds of molecules and its transfer/addition to another molecule (ex. ADP + PO = ATP)
- Substrate level - transfer of phosphate to ADP from another phosphorylated organic compound
- Oxidative - energy from redox reactions to attach inorganic phosphate to ADP
- Photo - light energy used to attach inorganic phosphate to ADP
31
What are redox reactions?
Electrons being transferred from a donor to an acceptor.
The acceptor is "reduced" and the donor is "oxidized".
OIL RIG (oxidation involves loss; reduction involves gain)
32
In the first step of glycolysis (EMP), how does phosphorylation differ between bacteria and eukaryotes?
Glucose in bacteria is phosphorylated via group translocation. They do not have the enzyme, hexokinase, to complete this step.
33
Differentiate the 3 main metabolic pathways by their final electron acceptor.
Aerobic respiration - oxygen
Anaerobic respiration - nonorganic compounds (ex. sulfate, nitrate, carbonate)
Fermentation - organic compounds
34
What is the pentose phosphate pathway?
An alternative to glycolysis for the breakdown of glucose which produces a phosphorylated 5-carbon sugar and NADPH.
35
Describe glycolysis (EMP) and its purpose/function?
It is the partial oxidation of a glucose molecule and produces a net: 2 ATP, 2 NADH, and 2 pyruvic acid.
Pyruvic acid is a starting molecule required for respiration and fermentation and has lots of energy stored in its bonds that the cell needs.
36
Can pyruvic acid be used in the Krebs cycle?
No, pyruvic acid must be converted to acetyl-CoA first.
37
What are the 3 stages of glycolysis (EMP)?
1. Energy investment stage:
Starting with 1 glucose molecule, 2 ATP are invested to ultimately form 1 fructose 1,6-biphosphate.
2. Lysis stage:
Fructose 1,6-biphospate is split to form 1 G3P and 1 DHAP (which is then rearranged to G3P for a total of 2 G3P)
3. Energy conservation phase:
Each G3P is converted to pyruvic acid, and in the process produces 2 ATP and 1 NADH per 1 G3P.
Total net products of glycolysis is:
2 ATP
2 pyruvic acid
2 NADH
38
What are the enzymes involved in glycolysis (EMP)?
*Key things to remember*
- Kinase: transfers phosphate groups, will use or form ATP
- Isomerase: rearranges molecules like DHAP/G3P
- Dehydrogenase: involved with ETC and electron carriers
Energy investment stage (uses 2 ATP):
1.) Glucose -> Glucose 6-P = hexoKINASE (bacteria use group translocation)
2.) Glucose 6-P -> Fructose 6-P = phosphoglucose ISOMERASE
3.) Fructose 6-P -> Fructose 1,6-BP = phosphofructo-KINASE
Lysis stage (makes 2 G3P):
4.) Fructose 1,6-BP -> G3P/DHAP = fructose biphosphate ALDOLASE
5.) DHAP -> G3P = triose phosphate ISOMERASE
Energy conservation phase (makes 4 ATP, 2 NADH, 2 pyruvic acid):
6.) G3P donates phosphate group to NAD = G3P DEHYDROGENASE (results in NADH and 1,3 BPG acid)
7.) 1,3 BPG -> 3PG = phosphoglycerate KINASE
8.) 3PG -> 2PG = phosphoglycerate MUTASE
9.) 2PG -> PEP = ENOLASE (releases H2O)
10.) PEP -> pyruvic acid (pyruvate KINASE)
39
What are the final NET products of glycolysis?
2 pyruvic acid (pyruvate)
2 NADH
2 ATP
40
What are the 2 different pathways after glycolysis? What do they rely on?
Respiration (aerobic or anaerobic) or fermentation. Depending on the final electron acceptor available, this will influence the pathway taken.
Aerobic respiration - oxygen
Anaerobic respiration - nonorganic compounds (ex. sulfate, nitrate, carbonate)
Fermentation - organic compounds
41
Describe synthesis of acetyl-CoA
Start with: pyruvic acid
- 3-carbon molecule. Remove a CO2 and add coenzyme A. Produces 1 NADH in the process.
End with: acetyl-CoA
- 2-carbon molecule
1 glucose makes 2 pyruvic acid, therefore 1 glucose makes:
2 acetyl-CoA
2 NADH
2 CO2
42
Briefly describe the Krebs cycle and its NET production.
A continuous cycle of reactions in which energy is released from the bonds of Acetyl-CoA and transferred to the electron carriers NAD+ and FAD.
Only 1 acetyl-CoA enters the Krebs cycle at a time, therefore 2 cycles for the 1 original glucose molecule:
Net production (2 cycles):
2 FADH2
6 NADH
2 ATP (indirectly from GTP)
4 CO2
43
What are the types of reactions in the Krebs cycle?
- Anabolism
- Isomerization
- Redox reactions
- Decarboxylation
- Substrate-level phosphorylation
- Hydration
44
When acetyl-CoA first enters the Krebs cycle, what is it joined by and what is the product made?
It is joined by oxaloacetic acid to form citric acid.
45
Why is the electron transport chain located in the cell membrane?
1.) Carriers must be in close proximity to each other to pass and receive electrons
2.) The goal of ETC is to pump protons to create an electrochemical gradient. Without the membrane, there could be no gradient.
46
Briefly describe the electron transport chain (ETC)
Series of redox reactions by membrane carriers that accept and donate electrons.
Each time an electron is passed, it loses some energy and is passed to a final accept molecule at the end of the ETC.
The energy being lost between each "pass" pumps protons across the membrane to create an electrochemical gradient (also known as: potential energy, proton gradient, or proton motive force).
47
What are some types of carriers in the electron transport chain?
Flavoproteins: integral protein carrier
Ubiquinones: non-protein carrier
Metal-containing proteins: integral protein carrier
Cytochromes: integral protein carrier
48
What is the significance of the cytochrome oxidase carrier?
It is the final carrier in the ETC in some bacteria.
It can also be used in metabolic characterization by the oxidase test.
49
Describe chemiosmosis
Process in which the cell's electrochemical gradient's potential energy (proton motive force) is used to generate ATP.
The protons are initially pumped across the membrane during the ETC to create the gradient and then flow down through ATP synthase which phosphorylates ADP to ATP (34 ATP made from the ETC/chemiosmosis).
ETC pumps 3 pairs of protons from NADH and 2 pairs for FADH2.
50
Why does NADH pump more protons than FADH2?
NADH is more electronegative and delivers electrons earlier in the ETC than FADH2 does.
51
Do all carriers in the ETC accept both electrons AND protons?
No, the membrane carriers in the ETC alternate between accepting both (protons and electrons) and only electrons.
52
What are some poisons that inhibit cell respiration?
Arsenic - stops formation of acetyl-CoA (needed for Krebs)
Mercury - stops redox reactions in ETC
Cyanide - prevents final transfer of electron to oxygen (halts ETC reactions)
Carbon monoxide - blocks final transfer of electron to oxygen (halts ETC reactions)
53
Why does aerobic respiration create more ATP than anaerobic respiration?
Oxygen, the final electron acceptor in aerobic respiration, is the most electropositive and due to the electrochemical gradient, is able to pump more protons through ATP synthase quicker to produce more ATP.
54
Describe fermentation and its ultimate goal.
The incomplete oxidation of glucose when the cell cannot complete either type of respiration due to lack of oxygen/inorganic electron acceptors. Fermentation uses an organic molecule as its final electron acceptor.
Its goal is not necessarily to produce ATP but to free up/oxidize NADH so glycolysis can use them (and create the 2 ATP during the process)
55
What are the types of fermentation?
Lactic acid:
- homolactic (makes acid only)
- heterolactic (makes acid AND other compounds)
Alcohol: makes ethanol and CO2 (through decarboxylation)
56
Summarize net ATP production in the various pathways of glucose catabolism
Glycolysis: 2 ATP
Krebs cycle: 2 ATP (indirectly from GTP)
ETC: 34 ATP (prokaryotes), 32 ATP (eukaryotes)
Respiration overall:
- Aerobic: 38 ATP (prokaryotes), 36 (eukaryotes)
- Anaerobic: 2-36 ATP
Fermentation: technically 0 ATP (it oxidizes NADH so glycolysis can make 2 ATP)
57
What other things can cells catabolize for energy? Which is preferred and why?
Lipids and proteins.
Lipids are preferred over proteins because:
1.) Lipids make more ATP than proteins
2.) Proteins are essential to cell function
3.) Protein catabolism creates more waste
58
Describe lipid catabolism.
Lipases break down lipids into:
Glycerol: converted to DHAP (which can be easily converted into G3P for use in glycolysis)
Fatty acids (carbon chains): beta-oxidized to form acetyl-CoA (for Krebs cycle), NADH, and FADH2 (for ETC)
59
Describe protein catabolism.
Proteases break proteins into amino acids.
Deamination then removes their amino groups to feed into Krebs cycle.
60
Describe photosynthesis.
Capturing light energy, using redox reactions to store it in ATP and NADPH, and using that energy to synthesize glucose from CO2.
61
What are the reactions in photosynthesis?
Light-dependent reactions:
- Pigments (chlorophylls) in photosystems capture light energy and excite electrons donated by H2O (oxidation), which release oxygen.
- The energized electrons travel down electron transport chains and pump protons across the cell's membrane, to establish electrochemical gradient (like respiration).
- Protons flow through ATP synthase creating ATP via chemiosmosis (and NADPH).
Light-independent reactions (Calvin cycle):
- Uses ATP and NADPH in the carbon fixation step of the Calvin cycle.
- Phosphorylation and redox reactions use CO2 (and RuBP) to create G3P molecules and regenerate RuBP.
- 2 G3P molecules are polymerized to form 1 glucose.
62
Briefly describe anabolic pathways (synthesis) for: 1.) carbohydrates, 2.) lipids, 3.) amino acids, 4.) nucleotides
Carbohydrates: Calvin cycle
- sugars used in starch, cellulose, peptidoglycan
Lipids: glycerol made from G3P; fatty acids made by linking acetyl-CoA together into chains
- lipids used in membranes/phospholipid bilayers, mycolic acid
Amino acids: precursors from Krebs cycle and 5-carbon sugars from pentose phosphate pathway (glycolysis alternative)
- proteins
Nucleotides: 5-carbon sugars, phosphate from ATP, nitrogenous bases from amino acids and Krebs cycle
- DNA/RNA
63
When reading a biochemical test, what color indicates that bacteria can ferment a sugar?
Yellow due to lowering of pH by acids (with or without gas production)
64
How can we classify bacteria based on optimum growth temperature?
Psychrophiles - low temp, below 20C
Mesophiles - medium temp, 20-40C (most pathogens)
Thermophiles - high temp, above 45C
Hyperthermophiles - extremely high, above 80C
65
Classify bacteria by pH levels
Neutrophiles - grow in neutral conditions
Acidophiles - lower pH
Alkalinophiles - higher pH
- Bacteria 6.5-7.5 pH
- Yeasts 5-6 pH
66
Group bacteria based on the different types of water pressure.
Obligate halophiles - require higher osmotic pressure, up to 30% salt
Facultative halophiles - indifferent to osmotic pressure (2-15% salt)
Barophiles - live under extreme hydrostatic pressure
67
Differentiate between the following terms:
- Sterilization
- Disinfection
- Disinfectants
Sterilization: removal or destruction of ALL microbes on an object
Disinfection: use of chemicals (disinfectants) to inhibit or destroy pathogens on non-living objects
Disinfectants: chemical agents applied to surfaces of non-living objects
68
Differentiate between the following terms:
- Sanitization
- Degermation
Sanitization: disinfecting an object used in public to reduce number of pathogens (think utensils)
Degermation: removal of microbes by scrubbing
69
Differentiate between the following terms:
- Sepsis
- Antisepsis
- Antiseptics
Sepsis: growth of microorganisms in the blood and other tissues
Antisepsis: inhibition/killing of microorganisms on skin/tissue by use of chemicals (antiseptics)
Antiseptics: chemical agents applied directly to exposed body surfaces, wounds, and surgical incisions
70
Antimicrobial processes vs. antimicrobial agents
- Sterilization and disinfection are "processes"
- Germicide/microbicide are "agents"
Static vs Cidal:
-static/stasis = inhibits microbes
-cidal/cide = kills microbes
71
What is pasteurization?
Pasteurization: using heat to kill and control microbes from spoiling food/drink
72
What are some physical methods of microbial control?
Moist heat:
- Boiling
- Autoclave
- Ultra-high temperature sanitization
Dry heat:
- Incineration
- Hot air
Refrigeration or freezing
Desiccation (drying)
Lyophilization (freeze-drying)
Filtration
Osmotic pressure
Radiation
73
List the different types of microbes in order from highest to lowest resistance
(Most resistant)
Prions
Bacterial endospores (extreme resistance)
Mycobacteria (waxy layer)
Protozoa
Gram-negative bacteria (double membrane + LPS)
Fungi
Nonenveloped viruses (resistant to heat)
Gram-positive bacteria (single membrane)
Enveloped viruses (envelope removal hinders attachment)
(Most susceptible)
74
Briefly describe the 4 Biosafety Levels
BSL-1:
- Handling microbes that do not cause disease in humans
- Precautions: Hand washing with antibacterial soap & washing surfaces with disinfectants
BSL-2:
- Handling moderately hazardous agents
BSL-3:
- All manipulations of microbes done in safety cabinets with HEPA filters
BSL-4:
- Handling microbes that cause severe or fatal disease
- Lab space is isolated, and personnel wear protective suits
75
What are some ways to control microbial growth?
Physical agents:
- Heat (dry or moist)
Chemical agents:
- Gases or liquids
Mechanical removal
- Filtration or scrubbing
76
What is microbial death?
Permanent loss of reproductive capacity
77
Why might you measure the microbial death rate?
To determine the efficacy of an antimicrobial agent
78
What are some factors that affect the efficacy of antimicrobial methods?
Site to be treated
- Will it harm human or damage object?
Susceptibility and number of microbes
Environmental conditions
- Warm works better then cold (faster reactions)
- Acidity enhances effects of heat
- Organic materials (feces, blood, etc.) can interfere with penetration
Time/length of exposure
Concentration of agent
- Higher may be more toxic to humans
79
What are some targets for chemical or physical antimicrobial methods?
Cell wall
- Osmotic pressure
Cell membrane
- Contents may leak out
- Chemicals may enter cell
- Attachment issues for enveloped viruses
Proteins
- Denature proteins or enzymes
- Disrupt DNA/RNA
80
Describe the levels of susceptibility of chemicals
High: kills all pathogens including endospore
Intermediate: kills fungal spores, protozoan cysts, viruses, and pathogenic bacteria
Low: kills vegetative bacteria, fungi, protozoa, some viruses
81
Briefly describe phenolics
- Intermediate to low level
- Denatures proteins
- Disrupts cell membranes
- Used as disinfectants or antiseptics
- Chlorhexidine
82
Briefly describe alcohols
- Intermediate level
- Denature proteins
- Disrupt cell membranes
- 70-90% solution
- Disinfectants/antiseptics
83
Briefly describe halogens
- Intermediate level
- Denatures proteins
- Disinfectant and antiseptics
- Chlorine, bromine, iodine, fluorine
84
Briefly describe oxidizing agents
- High level
- Denature proteins
- Disinfectants/antiseptics
- Use in wounds or medical equipment
- Hydrogen peroxide
85
Briefly describe surfactants
- Low level
- Disrupt cell membranes
- Soaps or detergents
86
Briefly describe Aldehydes
- High level
- Denature proteins
- Disinfectants or embalming fluids
- Formaldehydes, glutaraldehydes
87
Briefly describe gaseous agents
- High level
- Denature proteins
- Sterilize equipment
- Beta-propiolactone, ethylene oxide, propylene oxide
88
Describe 3 methods for evaluating effectiveness of disinfectants/antiseptics.
Use-dilution test
- Dips metal cylinders into broth cultures and place them into various dilutions of chemical agent to check for growth
- Standard test in USA
Kelsey-Sykes capacity test
- Bacteria added to chemical being tested to determine ideal disinfectant concentration
In-use test
- Swab surface before and after chemical agent is applied
- Provides most accurate "real-life" conditions efficacy results
89
What is antimicrobial selective toxicity?
Toxicity to pathogens without being toxic or harming the human patient
90
What are some goals of antimicrobial chemotherapy?
To kill the pathogen(s) that are causing harm to a patient without harming them.
Drugs must be:
- Easily administered
- Able to reach pathogen anywhere in body
- Toxic to pathogen/nontoxic to patient
- Remain active as long as needed but easily excreted when finished
91
Define the following terms:
- Prophylaxis
- Antimicrobials
- Antibiotics
- Semisynthetic
- Synthetic
- Narrow and Broad Spectrum
Prophylaxis - use of a drug to prevent infection of a person at risk
Antimicrobial - term for any drug that inhibits/kills microbes
Antibiotic - inhibits/kills only bacteria
Semisynthetic - chemically modified in the laboratory
Synthetic - produced entirely in the laboratory
Narrow-Spectrum - effective against limited microbe types (ex. against mainly gram-positive bacteria)
Broad-Spectrum - effective against a wide variety of microbes (ex. against both gram-positive/negative)
92
What are some things you should know before antimicrobial treatment begins?
- Identity of microorganism
- Microorganism's sensitivity or susceptibility to various drugs
93
What are 2 ways to determine a microorganism’s susceptibility to a drug? (what tests?)
Disk-Diffusion Test:
- Agar plate spread with bacteria
- Discs with known amount of antibiotic placed onto plate
- Zone of inhibition are measured
Tube Dilution Test:
- Serial dilution of antibiotic placed into multiple tubes
- Each tube inoculated with same amount of bacteria
- The smallest concentration (highest dilution) of drug that inhibits growth is the Minimum Inhibitory Concentration (MIC):
94
What are some mechanisms of action of antimicrobial drugs?
- Inhibition of cell wall synthesis
- Inhibiting protein synthesis (ex. different ribosome sizes)
- Degrading cell membrane
- Interfering with non-human metabolic pathways (ex. folic acid synthesis)
- Inhibition of DNA/RNA synthesis (ex. gyrase)
- Blocking pathogen's recognition of or attachment to host cells
95
How do biofilms affect antimicrobial drugs?
Bacteria in biofilms express different phenotypes than when free-living (planktonic). Therefore, bacteria living in biofilms may have different antibiotic susceptibility.
Additionally, antibiotics often cannot penetrate the extracellular polysaccharide layer they produce.
96
What is the problem with trying to treat fungal infections?
Fungal cells are eukaryotic, so their drugs can also be toxic to humans. Additionally, drugs used against bacteria are often ineffective.
Only a few antifungal drugs have been developed.
97
What are some treatments for protozoal infections?
- Anti-malarial drugs
- Amoebicides
98
Briefly describe helminth infection treatment.
Larger parasites are physiologically similar to humans, therefore treatment can be problematic.
Most helminth infections are treated with drugs that immobilize, disintegrate, or inhibit metabolism.
99
Describe viral infection treatment.
Since viruses replicate inside host cells (and you cannot disrupt host cell metabolism), drugs target viruses by:
- inhibiting viral entry (receptors, fusion, or uncoating)
- inhibiting nucleic acid synthesis (only if targeting enzymes such as viral RNA-dependent RNA polymerase)
- inhibiting viral assembly or release
100
Describe antimicrobial resistance
Microbes begin to tolerate certain drugs that would normally be inhibitory/destructive
101
What are 2 ways that cells become resistant to antibiotics?
- Random mutations
- Acquisition of resistance genes via horizontal gene transfer
102
How does natural selection play a role in resistance?
Natural selection does not cause resistance since it is random.
However, it enables an increase in the population of resistant bacteria by:
- antibiotics kill bacteria without resistance
- resistant bacteria survive and have more access to nutrients
- resistant bacteria grow exponentially
- may pass genes via horizontal gene transfer or new resistance via random mutation
(Ex. killing all good bacteria that are part of normal microbiota which compete with the bad)
103
What are some ways to replenish your normal microbiota?
Probiotics - live microbes fed to animals and humans to improve intestinal biota
Prebiotics - nutrients that encourage the growth of beneficial microbes in the intestine
Fecal transplants - transferring feces from a healthy patient to a sick
104
What are some organs that can be negatively affected by antimicrobial drugs?
- Liver (hepatotoxic)
- Kidneys (nephrotoxic)
- Gastrointestinal tract
- Cardiovascular system and blood-forming tissue (hemotoxic)
- Nervous system (neurotoxic)
- Respiratory tract
- Skin
- Bones and teeth
105
Why do some patients have allergic reactions to antimicrobial drugs?
Drugs can act as antigens that stimulate the body's immune response.
Reactions can include: hives, respiratory inflammation, or anaphylaxis.
The most common drug allergy is penicillin.
106
What are some measures we can take to prevent antibiotic resistance?
- Only use antibiotics for treating bacteria
- Don't take them when you are infected by a virus
- Control the sale/possession of antibiotics
- Ensure use of the correct antibiotic to treat the appropriate type of bacteria (i.e. don't use an incorrect narrow spectrum antibiotic)
- Take precautions when infected, so not spread or transmit the infection to others
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What are some mechanisms of antibiotic resistance?
- Producing enzymes that destroy drug
- Preventing or slowing entry of drug into cell
- Altering target of the drug (so cannot bind)
- Alter cell's metabolic processes (ex. abandon folic acid synthesis and absorb from environment)
- Use efflux pumps to get rid of drug
- Reliance on biofilms
- Production of harmless molecules that compete with drug's target receptor
108
What are some characteristics of the influenza virus?
- Segmented RNA genome (7-8 segments/strands)
- negative-sense, ssRNA
- Contains genes for RNA-dependent RNA polymerase (due to negative sense)
- Enveloped
- 2 glycoproteins: Hemaglutinin and Nueraminidase
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What causes genetic drift in the influenza virus?
Influenza virus's RNA dependent RNA is not extremely accurate and may make errors during transcription, causing small changes.
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What causes antigenic shift in the influenza virus?
Remember that the genome of influenza virus is a segmented. Two different types of influenza viruses infect the same cell and reassemble their different segments into a new viral strain.
111
What are the 5 major targets for antimicrobial drugs?
Plasma membrane
- contents control/nutrient transport
- electron transport chain
Ribosomes
- prevent peptide bond formation
- promoter region
- 70S in prokaryotes
Metabolic pathways
- prevent growth
- impede nutrient catabolism/anabolism
- hinder structure production
DNA/RNA synthesis
- limit binary fission
- stop transcription
Cell wall
- lysis (due to osmotic pressure)
- cease peptidoglycan production
112
Briefly characterize the following antibiotic:
- Penicillin G
Penicillin G
- inhibits cell wall (peptidoglycan bonds)
- narrow spectrum (G+)
- selectively toxic (humans don't have cell walls)
- bacterial resistance by preventing entry, prevent drug binding via enzyme modification, inhibit drug itself
113
Briefly characterize the following antibiotic:
- Bacitracin
Bacitracin
- inhibits cell wall synthesis
- narrow spectrum (G+)
- selectively toxic (humans don't have cell walls)
- bacterial resistance by preventing entry into cell
114
Briefly characterize the following antibiotic:
- Erythromycin
Erythromycin
- inhibits protein synthesis (50s subunit)
- broad spectrum (G+ and few G=)
- selectively toxic (humans don't have 50s subunit)
- bacterial resistance by prevent drug binding, destroy drug itself
115
Briefly characterize the following antibiotic:
- Tetracycline
Tetracycline
- inhibits protein synthesis (30s subunit)
- broad spectrum
- selectively toxic (humans don't have 30s subunit)
- bacterial resistance by prevent drug entry, alter ribosome binding site, pump drug from cell
116
Briefly characterize the following antibiotic:
- Polymyxin
Polymyxin
- inhibits function of cell membrane LPS layer
- narrow spectrum (G=)
- selectively toxic (humans don't have LPS)
- bacterial resistance by preventing entry of drug into cell
117
Briefly characterize the following antibiotic:
- Trimethroprim
Trimethroprim
- inhibits folic acid metabolism
- broad spectrum
- selectively toxic (humans do not produce folic acid)
- bacterial resistance by permeability and folic acid uptake via environment
118
Briefly characterize the following antibiotic:
- Ciprofloxacin
Ciprofloxacin
- inhibits DNA gyrase/DNA synthesis
- broad spectrum
- selectively toxic (humans don't have DNA gyrase)
- bacterial resistance by slowing entry, protecting DNA gyrase, and random mutations
