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PHAM02 > UV radiation > Flashcards

UV radiation Flashcards

1
Q

3 types of UV light and what they do

A

UV-A: doesn’t cause sunburn but can still cause skin cancer through free radical formation, lowest energy, not absorbed by ozone layer, less biological damage, indirect DNA damage

UV-B: causes sunburn and directly damages DNA, mostly absorbed by ozone layer, eye damage, skin/ageing, sunburn/cancer, direct DNA damage

UV-C: completely blocked by the ozone layer, highest energy and most damaging

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2
Q

benefits of UV-B

A

causes body to produce vitamin D

need some UV-B radiation to maintain adequate vitamin D levels

15mins sun exposure a few times a week

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3
Q

How the UV lights are abrorbed by the skin?

-> WAVELENGTHS

A

UV-A: penetrates all the way through skin to dermis and SC layer

UV-B: penetrates to epidermis and dermis

UV-C: doesn’t reach skin, but would be absorbed by stratum corneum and epidermis

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4
Q

What type of damage does UV-B cause?

A

intramolecular reactions with DNA

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5
Q

2 types of dimers that UV-B can cause?

A
  1. cyclobutane pyrimidine dimers 80%
  2. oxetane pyrimidine dimers 20%
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6
Q

How do cyclobutane pyrimidine dimers occur from UV-B?

A

strong covalent bonds link together 2 adjacent (on same strand) thymine bases - intrastrand

causes direct DNA damage

disrupts the DNA strand so it can’t be copied by DNA polymerase
- errors introduced into the base sequence

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7
Q

oxetane pyrimidine dimer formed from UV-B

A

covalent link together 2 adjacent thymine bases (intrastrand)

the oxetane ring collapses to a pyrimidine-pyrimidone dimer

causes direct DNA damage

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8
Q

indirect damage, especially by UV-A

A

formation of free radicals

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9
Q

2 types of free radicals that can be formed that damage DNA

A

superoxide radical

hydroxyl radical

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10
Q

What can free radicals interact with and damage?

A

proteins, lipids in cell membrane

RNA, DNA in nucleus

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11
Q

What type of damage do free radicals cause DNA?

A

indirect damage

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12
Q

What type of UV light can cause formation of free radicals?

A

UV-A and UV-B

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13
Q

What do free radicals interact with in body?

A

guanine

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14
Q

What is formed from interaction between free radicals and guanine?

A

8-oxoguanine

-> occurs indirectly

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15
Q

What can happen with 8-oxoguanine?

A

8-oxoguanine pairs with adenine - Hoogsteen pairing

this mis-pairing requires repair ir can lead to mutations

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16
Q

What is the Hoogsteen pairing?

A

pairing of 8-oxoguanine to adenine

17
Q

apoptotic mechanisms and age

A

apoptotic mechanisms decline with age

18
Q

sun protection granules in the skin

A

melanin

made by melanocytes in basal layer and stimulated by direct UV radiation

19
Q

What UV radiation causes sun burn from direct damage to DNA?

A

UV-B

20
Q

What is the constant triggering and suppression of melanocytes that causes uneven pigmentation and spots called?

A

age apots

21
Q

What is leathery/rough/uneven skin texture called?

A

elastosis

22
Q

SPF

A

sun protection factor

23
Q

2 factors in sun cream

A

SPF

star rating

24
Q

What is SPF and what does it do?

A

multiple by which person can stay in the sun without burning/damage after applying the porduct compared to the time they could spend in the sun withoug burning/damage with no protection

protects skin from harmful effects of UV-B radiation for a specific amount of time

25
Q

What does SPF protect from?

A

UV-B

26
Q

What does star rating protect from?

A

UV-A

27
Q

How do the organic UV filters in sun creams work?

A

absorb UV radiation by chromophores at specific wavelengths and release it at a much lower energy that is not damaging

28
Q

What types of organic UV filters are used in sun creams?

A

aromatics conjugated with carbonyls

29
Q

How do inorganic UV filters in sun cream work?

A

physical UVfilters

have high refractive index

reflect, scatter and may absorb UV radiation

30
Q

examples of UV inorganic filters used for UV-A and UV-B

A

UV-A: zinc oxide

UV-B: zinc oxide, titanium dioxide

31
Q

What should good sun cream contain?

A

combination of inorganic and organic UV filters

32
Q

What do film formers do in sun cream?

A

used to create a layer of UV filters on the skin

adherance to straum corneum

resistance to water/sweat/rub off

33
Q

What do antioxidants do in sun cream?

A

absorb free radicals on the skin surface

free radicals formed by UV radiaiton

34
Q

examples of antioxidants

A

Vit A, C, E

piperidine nitroxide

rutin (a flavonoid)

BHT - t-butylhydroxytoluene

35
Q

What do anti-inflammatories to in sun cream?

A

slow progression of UV damage leading to skin damage

interfere with skin response to damage by stopping the biological cascade reaction

reduce reddening, pain, blistering, peeling effect of sunburn

doesn’t stop DNA damage so ageing/cancer can still progress

PHAM02 (32 decks)

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