Unit 2-Skin Care Flashcards
What name is given to the high energy radiation from the sun which can damage skin?
Ultraviolet radiation (UV)
What effect does UV have on the human body?
Causes sunburn and contributes to ageing of the skin.
What effect does exposure to UV light have on molecules?
Molecules gain enough energy for bonds to be broken.
How do sun-block products work?
Sun-block products prevent UV light reaching the skin.
What can be formed when bonds are broken by UV light?
Free radicals
What is a free radical?
Free radicals are highly reactive species/substances that have one unpaired electron.
What are the three steps in a free radical chain reaction?
- Initiation.
- Propagation
- Termination
Describe the initiation stage in a free radical chain reaction.
UV light is absorbed and bonds split forming free radicals.
Describe the propagation stage in a free radical chain reaction.
The original free radicals react with another molecule, become stable and form new reactive free radicals.
Describe the termination stage in a free radical chain reaction.
Two free radicals combine to form stable oxidation products.
Are the following reactions initiation, propagation or termination steps?
A. Cl· + Cl· –> Cl2
B. Cl· + CH4 –> CH3· + HCl
C. CH3· + Cl· –> CH3Cl
D. Cl2 –> Cl· + Cl·
A is a termination step
B is a propagation step
C is a termination step
D is an initiation step
What is meant by a free radical scavenger?
Free radical scavengers are molecules which can react with free radicals to form stable molecules
OR
Donates electron(s).
OR
Acting as a reducing agent.
Free radical scavengers can be added to food products.
Name another product which has added free radical scavengers.
Sun blocks
or
Cosmetics
or
Plastics
