Unit 2 - Nature's Chemistry (Skincare)

Question 1

What are the three types of UV radiation in order of increasing frequency?

Answer 1

UVA, UVB, and UVC

Question 2

What damage does UV radiation cause on our skin?

Answer 2

All three forms affect the breakdown of collagen in our skin, which can lead to premature ageing.

Question 3

How can we protect ourselves from harmful UV rays?

Answer 3

Sunblock is commonly used to prevent damage to the skin by preventing harmful UV radiation from being absorbed.

Question 4

What are some forms of physical protection from UV radiation?

Answer 4

Titanium dioxide and zinc oxide - block and scatter the rays before they penetrate the skin.

Question 5

What are some forms of chemical protection from UV radiation?

Answer 5

Avobenzone and octisalate - aborb UV rays before they damage the skin.

Question 6

What are free radicals?

Answer 6

Highly reactive atoms that have one unpaired electron.

Question 7

How are free radicals formed?

Answer 7

Radicals can be formed when a covalent bond is broken by energy supplied by UV light.

Question 8

What are the three types of chain reaction caused by free radicals?

Answer 8

• Initiation
• Propagation
• Termination

Question 9

What is needed for the initiation stage to occur?

Answer 9

UV light

Question 10

What side of the initiation reaction are the unpaired electrons situated?

Answer 10

The products side

Question 11

What side of the propagation reaction are the unpaired electrons situated?

Answer 11

Both sides

Question 12

When does termination occur?

Answer 12

When a reaction takes place in which no new radicals are formed. This can occur whenever radicals react with each other.

Question 13

When does propagation occur?

Answer 13

The highly reactive radicals formed can remove atoms from other (stable) compounds to re-establish stable covalent bonds. This reaction will produce a new free radical.

Question 14

What side of the termination reaction are the unpaired electrons situated?

Answer 14

The reactants side

Question 15

What are free radical scavengers?

Answer 15

Chemicals (usually vitamins, minerals or enzymes) that react with and destroy free radicals. By reacting with any free radicals present, the free radical scavengers prevent a chain reaction from occurring. This is often desirable to help protect our skin (so they are present in cosmetics) and our food (present both in some foods and in plastics).

Question 16

What do free radical scavengers tend to be?

Answer 16

Antioxidants