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Table 12.3 & 12.5

Micro-Chapter 12

Surfactants Dissolve lipids, disrupt membranes, denature proteins, and inactivate enzymes in high concentrations; act as wetting agents in low concentrations Cationic detergents are used to sanitize utensils; anionic detergents to launder clothes and clean household objects; quaternary ammonium compounds are sometimes used as antiseptics on skin.
Acids Lower pH and denature proteins Food preservation
Alkalis Raise pH and denature proteins Found in soaps
Heavy metals Denature proteins Silver nitrate is used to prevent gonococcal infections, mercury compounds to disinfect skin and inanimate objects, copper to inhibit algal growth, and selenium to inhibit fungal growth.
Halogens Oxidize cell components in absence of organic matter Chlorine is used to kill pathogens in water and to disinfect utensils; iodine compounds are used as skin antiseptics
Alcohols Denature proteins when mixed with water Isopropyl alcohol is used to disinfect skin; ethylene glycol and propylene glycol can be used in aerosols.
Phenols Disrupt membranes, denature proteins and inactive enzymes; not impaired by organic matter Phenol is used to disinfect surfaces and destroy discarded cultures; amylphenol destroys vegetative organisms and inactivates viruses on skin and inanimate objects; chlorhexidine gluconate is especially effective as a surgical scrub
Oxidizing agents Disrupt disulfide bonds Hydrogen peroxide is used to clean puncture wounds, potassium permanganate to disinfect instruments
Alkylating agents Disrupt structure or proteins and nucleic acids Formaldehyde is used to inactive viruses w/out destroying antigenic betapropiolactone to destroy hepatitis virus, and ethylene oxide to sterilize inanimate objects that would be harmed by high temperatures.
Dyes May interfere w/ replication or block cell wall synthesis Acridine is used to clean wounds, crystal violet to treat some protozoan and fungal infections
Dry heat Denature proteins Oven heat used to sterilize glassware and metal objects open flame used to incinerate microorganisms.
Moist heat Denature proteins Autoclaving sterilized media, bandages, and many kinds of hospital and laboratory equipment not damaged by heat and moisture; pressure cooking sterilized canned food
Pasteurization Denature proteins Kills pathogens in milk, dairy products, and beer
Refrigeration Slow the rate of enzyme-controlled reactions Used to keep fresh foods for a few days; does not kill most microorganisms
Freezing Greatly slows the rate of most enzyme-controlled reactions Used to keep fresh foods for several months; does not kill microorganisms; used w. glycerol to preserve microorganisms
Drying Inhibits enzymes Used to preserve some fruits & vegetables; sometimes used w/ smoke to preserve sausages and fish
Freeze-drying Dehydrations inhibits enzymes Used to manufacture some instant coffees; used to preserve microorganisms for years
Ultraviolet light Denatures proteins and nucleic acids Used to reduce the number of microorganisms in air in operating rooms, animal rooms, and where cultures are transferred
Ionizing radiation Denatures proteins and nucleic acids Used to sterilize plastics and pharmaceutical products and to preserve foods
Microwave radiation Absorbs water molecules, them releases microwave energy to surroundings as heat Cannot be used reliably to destroy microbes except in special media sterilizing equipment
Strong visible light Oxidation of light-sensitive materials Can be used w/ dyes to destroy bacteria and viruses; may help sanitize clothing
Sonic and ultrasonic waves Cause cavitation Not a practical means of killing microorganisms but useful in fractionating and studying cell components
Filtration membranes Mechanically removes microbes Used to sterilize media, pharmaceutical products, and vitamins, in manufacturing vaccines, and in sampling microbes in air and water
Osmotic pressure Removes water from microbes Used to prevent spoilage of foods such as pickles and jellies
Soaps & Detergents Lower surface tension, make microbes accessible to other agents Hand washing, laundering, sanitizing kitchen and dairy equipment
Created by: jenilee80