mcb lab quiz 11/2/26

What is radiant energy?

Energy that comes from the sun and other sources, differing in wavelength and energy.

What is the relationship between wavelength and energy?

Shorter wavelengths have greater energy and greater penetrating ability.

What are the two forms of radiant energy?

Ionizing radiation and non-ionizing radiation.

What is ionizing radiation?

Radiation that ionizes water into free radicals and can break DNA strands, e.g., gamma rays and X-rays.

What is non-ionizing radiation?

Radiation essential for biochemical processes, such as visible light and ultraviolet radiation.

What are the three types of ultraviolet (UV) radiation?

UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm).

What is the effect of UVB radiation?

Causes direct DNA damage and sunburn.

What is the role of photolyases in DNA repair?

Enzymes activated by light that split thymine dimers to restore DNA.

What is dark repair in DNA repair mechanisms?

Repair of DNA damage by endonucleases, DNA polymerase, and DNA ligase, independent of light.

What is the purpose of using UV radiation in sterilization?

To sterilize heat-labile solutions and disinfect environments, despite its poor penetrative ability.

What are germicides?

Substances that reduce the number of pathogens on surfaces, in liquids, or on living tissue.

What is the difference between disinfectants and antiseptics?

Disinfectants are used on inanimate objects, while antiseptics are used on living tissue.

What does bacteriostatic mean?

Inhibits cellular metabolism and growth, resulting in temporary inhibition of bacterial reproduction.

What does bactericidal mean?

Causes bacterial death by rupturing cell walls or membranes.

What is the decimal reduction time (DRT)?

The time it takes to kill 90% of the test microbial population.

Who discovered penicillin?

Alexander Fleming in 1928.

What is the Kirby-Bauer Test?

A standardized disk-diffusion test to determine the susceptibility of bacteria to antibiotics.

What is the significance of the zone of inhibition?

Indicates the effectiveness of an antibiotic by measuring the clearing around the disk.

What is the minimum inhibitory concentration (MIC)?

The lowest concentration of an antibiotic needed to effectively inhibit bacterial growth.

What is the Use-Dilution Test?

The official test for antiseptics and disinfectants, not to be confused with the Kirby-Bauer Test.

What is the role of actinomycetes in antibiotic production?

They are a major source of antibiotics, producing nearly 70% of all antibiotics.

What is the impact of broad-spectrum antibiotics on microbiomes?

They can alter our own microbiomes by killing many kinds of bacteria.

What are the two repair mechanisms for DNA damage caused by UV radiation?

Light repair (photoreactivation) and dark repair.

What is the effect of UVC radiation?

Similar to UVB but has stronger effects and is biocidal.

What is the purpose of the 3 + 1 method in the Kirby-Bauer Test?

To create a bacterial lawn for testing the effectiveness of antibiotics.

What factors must be considered when selecting antimicrobial agents?

pH, solubility, toxicity, organic material present, financial cost, and length of contact.

What happens to bacterial cells when chlorhexidine is used?

It binds to the cell wall, causing rupture and cell death.