UNIT 2 : Skin Care Flashcards
What is Ultraviolet (UV) radiation?
A high energy form of light from the sun
What are the three different wavelengths of UV radiation?
UV-A
UV-B
UV-C
What are the characteristics of UV-A radiation?
UV-A has the longest wavelength
Its is not absorbed by the ozone layer
Penetrates further than UV-B
What are the characteristics of UV-B radiation?
UV-B radiation is responsible for sunburn of the human skin
UV-B radiation is partially blocked by the ozone layer
What are the characteristics of UV-C radiation?
UV-C radiation is totally absorbed by the ozone layer
We would only encounter UV-C radiation from artificial radiation
What can happen to if substances are exposed to UV light?
Molecules can gain enough energy for bonds to be broken
What can happen if DNA is damaged?
Mutations are caused which stop the DNA functioning properly
What can DNA mutations produce in the body?
Tumours (groups of cells which have not been regenerated properly)
What is melanin?
A natural pigment that is produced when your skin is exposed to sunlight
What does melanin do?
It absorbs the UV radiation found in sunlight to help protect your skin
What does it mean if your skin goes darker after sun exposure, and what does this mean?
It goes darker (tan), a sign that skin has been damaged by UV rays
What breaks down when your skin is exposed to UV radiation?
Collegan
How are wrinkles formed?
Imperfect rebuilding of collagen fibers
What are the two main organic ingredients of sunscreen?
Titanium Oxide
Zinc Oxide
What happens when UV light breaks bonds?
Free radicals are formed
What is characteristic of free radicals?
They have a free electron, and thus are highly reactive
What are the three steps of free radical chain reactions?
Initiation
Propagation
Termination
What is homolytic fission?
When a reaction produces free radicals
What is hetrolytic fission?
When a reaction produces a set of ions which hold each other together
What is the symbol of a free radical?
A small dot after an element’s symbol
In the initiation stage, what type of fission takes place?
Homolytic
What happens in the initiation stage?
UV lights provides the energy for the homolytic fission of halogens into reactive halogen atoms or free radicals
In the initiation stage, what side of the reaction are the free radicals on?
Right hand side
What happens in the propagation stage?
Free radicals collide with other species but the number of free radicals stays the same
In the propagation stage, what side of the reaction are the free radicals on?
Free radicals are on either side of the reaction
In the termination stage, what side of the reaction are the free radicals on?
Left hand side
What happens in the termination stage?
Elements and compounds are formed
