T or F Micro 2 test

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The usefulness of agar in solidifying microbiological growth media is limited because it does not remain solid at temperatures about 28 degrees C.

False

Ultraviolet radiation is generally more harmful than ionizing radiation.

False

When a young, vigorously growing culture of bacteria is transformed to fresh medium of the different composition, the lag phase is usually short or absent.

False

The Michaelis constant (Km) of an enzyme is the substrate concentration that produces maximum velocity.

False

Blood agar is both a differential and enriched medium.

True

Alcohols are widely used as antiseptic and disinfectants because they are effective against endospores as well as vegetative cells.

False

Dry heat methods usually require lower temperatures and shorter exposure times than moist heat methods to achieve the same degree of killing because of the drying effects of this form of heat.

False

During the lag phase of microbial growth, the cells are metabolically inactive.

False

Germicides kill all pathogenic organisms and endospores.

False

Grisofulvin is used to treat systemic mycoses.

False

Phosphorous can be obtained from organic sources only.

False

A drug that disrupts a microbial function not found in animal cells usually has a lower therapeutic index.

False

A drug that disrupts a microbial function not found in animal cells usually has a higher therapeutic index.

True

Aerobic organisms do produce protective enzymes called superoxide dismutase and catalase.

True

Dry heat methods usually require higher temperatures and longer exposure times than moist heat methods to achieve the same degree of killing because of the drying effects of this form of heat.

True

Endospores have a high content of dipicolinic acid.

True

Ethylene oxide can be used to sterilize materials in sealed plastic wrap because it can penetrate the wrapping material.

True

Grisofulvin is used to treat superficial mycoses

True

Heavy metals are effective antimicrobial agents but are not widely used because of their high toxicity to humans.

True

One of the major advantages of a continuous culture system is that the cells can be maintained in the exponential growth phase for extended periods of time.

True

Penicillin is frequently injected but not normally given orally because it is rapidly degraded in the stomach.

True

Permease proteins that aid in the transport of nutrients resemble enzymes in their specificity for the substance to be transported. Each carrier is selective and will transport only a closely related set of substances.

True

The Michaelis constant (Km) of an enzyme is the substrate concentration that produces half velocity.

True

The effects of most antimicrobial drugs are greater if the microorganisms are actively growing.

True

The primary mechanism by which DNA is damaged by ultraviolet radiation involves the formation of thymine dimmers.

True

The rate of killing by an antimicrobial agent may slow when the microbial population has been greatly reduced because the remaining population may have a higher proportion of resistant organisms.

True

The trace amounts of micronutrients needed by microorganisms can usually be supplied in water and regular media components.

True

Treatment of fungal infections is more difficult than treatment of bacterial infections because the greater metabolic similarity between the fungi and their hosts limits the ability of a drug to have selective toxicity.

True

Ultraviolet radiation is an effective means of sterilizing surfaces.

True

Water activity is inversely proportional to osmotic pressure

True

When a young, vigorously growing culture of bacteria is transformed to fresh medium of the same composition, the lag phase is usually short or absent.

True


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