Lab 10 Flashcards
UV Light
UV radiation that reaches Earth is in the wave length range of
290 nm 400 nm
Wavelength range a visible light
400-700nm
What are the 3 types of UV radiation
UVA
UVB
UVC
What is the longest and shortest type of UV radiation
Longest–>UVA 320-400nm
Shortest–>UVC
What role does UVA play
Essential–>formation of vitamin D by the skin Harmful–>in that it causes sunburn on human skin and cataracts in the eyes
What type of radiation ranges at 290-320 nm
UVB
What type of radiation causes damage to DNA
UVB
What range is UVC radiation
100-280nm
Which type of UV radiation is the most dangerous and if filtered out by atmosphere
UVC
What type of UV radiation used for pond sterilization
UVC
How is UV light absorbed by DNA
Ultraviolet light is absorbed by a double bond in pyrimidine bases or purine bases. This opens the bond, allowing it to react with neighboring molecules. If it is next to another base, the UV modified base forms direct covalent bonds, forming a dimer
What are pyrimidine bases
Thymine, cytosine
What are purine bases
Adenine, guanine
Are bacteria capable of repairing UV damage
Many bacteria have enzymes that can repair DNA
What damage do base dimers cause
Say inhibit correct replication of the DNA during reproduction of the cell
Light repair
AKA Photo reactivation. In bacteria previously exposed UV light, light repair occurs in the presence of visible light that removes the dimers
Dark repair
Can take place in the presence or absence of visible light, requires several enzyme mediated reactions. The defective segment of DNA is removed and replaced
What are the 2 types of DNA repair
Light repair and dark repair
Are bacterial repair methods capable repairing all types of damage to DNA
The damage can be permanent if the exposure is for too long and mutations accumulate
Why is UV radiation useful as a microbicidal agent
Because microbes are single celled micro organisms and can be easily penetrated by UV
Why must object to be disinfected by UV radiation be directly exposed to it for full effect
Because UV radiation passes readily through air, slightly through liquids, and only poorly through solids
Name different ways UV radiation as used
- Germicidal lamp it’s commonly found in hospital room, operating rooms, cafeterias, nursing homes military housing, schools
- For disinfection of vaccines and other medical products
What is a major disadvantage of UV radiation
It penetrates poorly through solids or paper
What is another problem related to UV light
It can cause sunburn, retinal damage, skin wrinkles, and cancer.
