MCB 2610 Exam 2 All Possible Questions and Answers with complete solution
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MCB 2610
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MCB 2610
B-lactam resistance - Lactamases - enzymes that cleave beta lactam structure usually between
carbon and nitrogen - makes it no longer a structural mimic and transpeptidase keeps cross-linking
peptide side chains
Antimicrobial Agents - Agents that kill microorganisms or inhibit their growth
-cid...
MCB 2610 Exam 2
B-lactam resistance - Lactamases - enzymes that cleave beta lactam structure usually between
carbon and nitrogen - makes it no longer a structural mimic and transpeptidase keeps cross-linking
peptide side chains
Antimicrobial Agents - Agents that kill microorganisms or inhibit their growth
-cidal agents kill
-static agents inhibit growth
Household cleaners are disinfectants
14 out of 20 burn patients get pseudomonas infections from stainless steel tub cleaned with a quat..
why? - Quats do not kill pseudomonas
2 types of active transport - Primary active transporters (ABC) - use energy provided by ATP
hydrolysis to move substances against a concentration gradient
Secondary active transporters (MFS) - couple potential energy of ion gradients to transport substances
ABC transport system - Primary active transporters use ATP
ATP-binding cassette transporters
Consist of 2 hydrophobic membrane spanning transport proteins and 2 cytoplasmic associated ATP-
binding domains
Considered to be uniport - transports one molecule at a time
solute bingind protein located in periplasm of gram neg and external cytoplasmic membrane of gram pos
Binding proteins may also do chemotaxis
Active Transport - Energy dependent
Move molecules against gradient
Concentrates molecules inside cell
Involves specific carrier proteins (permeases)
,Alcohols - among the most widely used disinfectants and antiseptics
Two most common are ethanol and isopropanol
Not sporicidal
Inactivate some viruses
Denature proteins and possibly dissolve membrane lipids
Aldehydes - Commonly used agents are formaldehyde and glutaraldehyde
Highly reactive
Sporicidal and can be used as chemical sterilants
Combine with and inactivate nucleic acids and proteins
Cross-link macromolecules preventing functions
Antisepsis - Destruction or inhibition of microorganisms ON living tissue
Antiseptics
Asymmetry of most membrane lipids - Polar head with non-polar tail
B-Lactam antibiotics - Function by preventing cross-linking of peptidoglycan - initial bond
formation
Structure mimics D-ala-D-ala on peptide side chain
Transpeptidase gets confused and binds to penicillin thinking it will continue the peptide side chain -
inhibits growth
Bacterial Cell Wall - Peptidoglycan (murein) -
Rigid structure that lies just outside cell membrane
Two types based on gram stain (pos or neg)
, Bacterial cytoskeleton - Series of internal proteins keeping everything in the cell and moving
things to the right locations in cells
Bacterial Lipids - Very dynamic - saturation levels of membrane lipids reflect environmental
conditions
Bacterial membranes lack sterols but do contain sterol-like molecules - hopanoids - serve same purpose
as sterols and exactly like them - job is stability of membrane across temperature ranges
Balanced Growth - Cellular constituents manufactured at constant rates relative to each other
Best physical or chemical agents for sterilizing Glass pipets
Tryptic soy broth tubes
Antibiotic solution
Plastic-wrapped petri - Glass pipets - autoclave
TSB tubes - autoclave
Antibiotic solution - filtering
Plastic-wrapped petri dishes - ionizing radiation or sterilizing gases
Biosafety cabinet and other filtration devices - N-95 masks removes 95% of particles .3 um or
larger
High efficiency particulate air (HEPA) filters - used in laminar flow boisafety cabinets
Removes 99.97% of particles .3 um or larger
Calculating CFU/mL - Average cell number / (dilution X volume plated)
Cell Wall Functions - Maintains shape of the bacterium
Helps protect cell from osmotic lysis
Helps protect from toxic materials
May contribute to pathogenicity
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