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MO2 > UV radiation > Flashcards

UV radiation Flashcards

1
Q

what is the measurement of UV, visable and IR radiation?

A

UV : 10 to 400 nm
* Visible : 380 to 780 nm
* Infrared : 700 to 1,000,000 nm (1 mm)

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2
Q

how is UV light divided into ISO standard ranges?

A

– UV-A [400 –320 nm]
– UV-B [320 –280 nm]
– UV-C 280-100nm

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3
Q

what does UV-C do?

A

it is completely blocked by the ozone layer

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4
Q

what does UV-B cause?

A

sunburn and directly damages DNA

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5
Q

what does UV-A do?

A

does not cause sunburn although still thought to contribute to skin cancer through free radical formation

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6
Q

how is UV absorbed?

A

absorbed by nitrogen, oxygen, ozone and less than 5% of sunlight is in the UV
range at sea level

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7
Q

what kind of vitamin is vitamin D?

A

fat-soluble secosteroids
essential for life
can be obtained from food and supplements

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8
Q

what can happen if you are deficient in vitamin D?

A

deficiency can lead to bone-softening diseases
* rickets, osteomalacia, osteoporosis

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9
Q

what does vitamin D increase absorption of?

A

Ca2+, Mg2+, PO43-

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10
Q

what does vitamin D promote the biosynthesis of?

A

serotonin- increases mood

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11
Q

what causes the body to produce vitamin D?

A

UV-B

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12
Q

what is the most harmful type of radiation?

A

UV-C
completely absorbed in the ozone layer

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13
Q

what damage does UV-B do?

A

eye damage, skin ageing/damage, sunburn, skin cancer (direct DNA damage)

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14
Q

what does UV-A do?

A

– lowest energy
– not absorbed by the ozone layer
– does not cause sunburn
– does less biological damage, but not harmless
– eye damage, skin ageing/damage, skin cancer (indirect DNA damage)

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15
Q

how does the different types of UV radiation penetrate the skin?

A

UV-A
– penetrates all the way through the skin to the dermis and subcutaneous layer
* UV-B
– penetrates through the Stratum Corneum to the Epidermis and dermis
* UV-C (if any were to reach the skin)
– would be entirely absorbed by the stratum corneum and epidermis

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16
Q

how does UV-B cause DNA damage?

A

UV-B causes intramolecular reactions within DNA
– malignant melanoma (ca. 8% of cases)
– also possible with UV-A, but far less likely

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17
Q

why are two adjacent thymine bases are specifically venerable?

A

– dimers are formed
– DNA strand is bent from normal shape, and cannot be read properly by

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18
Q

UV-B causes the formation of cyclobutane pyrimidine dimers, what are these?

A

– strong covalent bonds link together two adjacent thymine bases (intrastrand)
– causes directDNA damage
– photochemical 2 + 2 cycloaddition
they disrupt DNA strand, so it cannot be accurately copied by DNA polymerase
and errors are introduced into the base sequence

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19
Q

UV-B damage can also cause the formation of oxetan pyrimidiner dimers, what are these?

A

covalent bonds link together two adjacent thymine bases (intrastrand)
– the oxetane ring collapses to a pyrimidine-pyrimidonedimer
– causes directDNA damage
– initially, a photochemical 2 + 2 cycloadditio

20
Q

what highly reactive substances can UV damage create?

A

highly reactive free radicals
- superoxide radical
hydorxyl radical

21
Q

what are potential damaging reactions with cell constituents?

A

– Proteins, lipids in the cell membrane
– RNA and DNA in the cell nucleus

22
Q

what UV light can produce free radicals?

A

both UV-A and UV-B can cause the production of free radicals

23
Q

what do free radicals do to DNA?

A

free radicals cause indirect damage to DNA
they modify guanine base structure

24
Q

what does a change in guanine structure cause?

A

causes mis-pairing
– normal : guanine pairs with cytosine (Watson-Crick pairing)
– mis-read : 8-oxoguanine pairs with adenine (Hoogsteenpairing)
– mis-pairing requires repair or can lead to mutations

25
Q

what does DNA damage due to UV exposure under normal circumstances cause?

A

leads to the arrest of the cell cycle
- DNA repair
-apoptosis

26
Q

what is an example for when apoptotic mechanisms decline with age?

A

if DNA repair or apoptosis does not occur then a genetic mutation will be
carried through replication processes

27
Q

what is the skin own sun protection granules? how are they made?

A
  • The skin has its own sun protection granules -melanin
    – dark brown in appearance
    – made by melanocytes in the basellayer and are stimulated by direct UV
    radiation
27
Q

what is the skin own sun protection granules? how are they made?

A
  • The skin has its own sun protection granules -melanin
    – dark brown in appearance
    – made by melanocytes in the basellayer and are stimulated by direct UV
    radiation
28
Q

after aprox 1 hour of exposure to sunlight, what appears on the skin?

A

melanin precursors appear in the skin
– bleached melanin already in the skin darkens

29
Q

how does delayed tanning work?

A

Delayed tanning occurs after ~2d exposure, peaking after 4-10d
– UV radiation stimulates the production of melanocytes –this produces more
melanin
– increased cell division at the basal layer -> more keratinocytes which carry
more melanin to the stratum corneum
– stratum corneum becomes tanned and thicker offering more protection than
untanned skin
– full tan develops in about 14 days and lasts for the lifespan of the epidermis

30
Q

how many different skin types are there?

A

6
type one fairest
type 6- darkest

31
Q

what mecanisms does direct damage caused by UV-B radiation trigger?

A

NA strands beyond repair trigger apoptosis
* peeling to remove irreparable skin cells and inflammation responses
– inflammation causes reddening through increased blood flow which makes
the area warmer
– release of prostanoidsand bradykinin lowers pain and heat receptor
thresholds

32
Q

how does skin damage affect aging?

A

constant DNA damage and repair causes natural errors in DNA replications
causing signs of ageing
* age spots –the constant triggering and suppression of melanocytes
causes uneven pigmentation and spots

33
Q

how does the skin elasticisty affect with aging?

A

elastosis -more noticeable in sun-exposed areas (solar elastosis)
– leathery, rough, uneven skin textur

34
Q

what is SPF?

A

Multiple by which a person can stay in the sun without burning/damage after
applying the product compared to the time they could spend in the sun without
burning/damage with no protection
protect from UV-B for a certain amount of time

35
Q

what does the star rating on sun cream measure?

A

measures UV-A protection
scale of 5 starts

36
Q

what are characteristics of a good suncream?

A

Bind well to the stratum corneum
* Resist rub-off and wash-off by water and sweat
* Are non-staining and non-toxic
* Absorb light effectively over a broad spectrum at low concentrations to minimise
risks of allergy and irritation.

37
Q

how do chemical sunscreens work?

A

absorb UV radiation into their molecular structure without chemical change
– high-energy (damaging) UV is absorbed by chromophores at specific wavelengths
and then released at much lower energy that is not damaging
blend of UV wavelengths

37
Q

how do chemical sunscreens work?

A

absorb UV radiation into their molecular structure without chemical change
– high-energy (damaging) UV is absorbed by chromophores at specific wavelengths
and then released at much lower energy that is not damaging
blend of UV wavelengths

38
Q

what are physical UV- filters?

A

– have a high refractive index
– reflect, scatter and may absorb UV radiation
– titanium dioxide (UV-B)
– zinc oxide0 and and b

39
Q

how can you boost protection in UV filters?

A

auxiliary ingredients

40
Q

what does effective UV protection require?

A

adherence to stratum corneum

41
Q

what are film formers used for?

A

Film formers are used to create a hardy layer of UV filters on the skin
– C20-40 alcohols, polyethylene, C30-38 olefin/isopropyl maleate/MA copolymer

42
Q

what is the purpose of antioxidants?

A

free radicals are quenched by antioxidants

43
Q

give example of antioxidants

A

– vitamin A, C, E
– piperidine nitroxide (TEMPOL)
– rutin(a flavonoid)
– t-butylhydroxytoluene (BH

MO2 (55 decks)

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