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PHAM02 > Wk 11: Causes of cancer - UV radiation (chemistry) > Flashcards

Wk 11: Causes of cancer - UV radiation (chemistry) Flashcards

1
Q

What is vitamin D?

A
  • Fat soluble secosteroids
  • Inc intestinal abs of Ca, Mg + PO
  • Promotes biosynthesis of serotonin
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2
Q

Deficiency of vitamin D can lead to what?

A

Bone softening disease:
- Rickets

  • Osteomalacia
  • Osteoporosis
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3
Q

What is serotonin?

A
  • Monoamine NT
  • Needed for: mood, cognition, reward, learning etc
  • Production proportional to sunlight
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4
Q

What is UV-B needed for?

A

Produces vit D - 15 mins casual exposure

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5
Q

What is UV-C?

A
  • Highest energy + most damaging
  • Blocked by ozone
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6
Q

What is UV-B?

A
  • Mostly abs by ozone
  • Eye damage, skin ageing, skin cancer
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7
Q

What is UV-A?

A
  • Lowest energy
  • Not abs by ozone
  • Doesn’t cause sun burn
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8
Q

How much does UV-A penetrate?

A

Through skin to dermis + SC layer

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9
Q

How much does UV-B penentrate?

A

Through stratum corneum to epidermis + dermis

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10
Q

How does UV-B cause DNA damage?

A

Causes reactions w/in DNA - forms dimers

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11
Q

What are dimers?

A

DNA strand bent from normal shape + cannot be copied by DNA polymerase

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12
Q

What are the 2 dimers UV-B can form?

A
  • Cyclobutane pyrimidine dimers (80%)
  • Oxetane pyrimidine dimers (20%)
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13
Q

How does UV-B form cyclobutane pyrimidine dimers?

A
  • Strong covalent bonds link 2 adjacent thymine bases
  • Cause direct DNA damage
  • Photochemical 2 + 2 cycloaddition
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14
Q

How does UV-B form oxetane pyrimidine dimers?

A
  • Covalent bonds link 2 adjacent thymine bases
  • Oxetane ring collapse to pyrimidine-pyrimidone dimer
  • Causes direct DNA damage
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15
Q

How else can UV light cause DNA damage?

A

Creates highly reactive free radicals:

  • Superoxide radical
  • Hydroxyl radical

Modifies guanine bases - causing indirect DNA damage

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16
Q

What do free radicals damage within cells?

A
  • Proteins + lipids in membrane
  • RNA + DNA in nucleus
17
Q

What is watson crick pairing?

A

Normal: guanine w/ cytosine

18
Q

What is hoogsteen pairing?

A

8-oxoguanine pairs w/ adenine

19
Q

What happens to apoptotic mechanism as you age?

A

Declines: more likely for mutations to be carried (cutaneous tumorigenesis)

20
Q

What is melanin made from?

A

Melanocytes in basal layer + stimulated by direct UV radiation

21
Q

What occurs in delayed tanning (2 days exposure)?

A
  • Peak 4-10 days
  • UV radiation stims prod of melanocytes = more melanin
  • Inc cell division at basal layer = more keratinocytes = more melanin to stratum corneum
  • Stratum = tanned + thicker for more protection
22
Q

What is type 1 skin?

A
  • Pale
  • Light eyes
  • Blond/red hair
  • Always burns, no tan
23
Q

What is type 2 skin?

A
  • Fair
  • Light eyes
  • Burns easily, may tan
24
Q

What is type 3 skin?

A
  • Medium
  • Initially burns then tans
25
Q

What is type 4 skin?

A
  • Light brown
  • Tans w/ minimal burns
26
Q

What is type 4 skin?

A
  • Medium brown
  • Rarely tans
27
Q

What is type 6 skin?

A
  • Dark
  • Easily tans + never burns
28
Q

What are the defence mechanisms of the skin after direct damage to DNA by UV-B radiation?

A
  • Apoptosis: peeling + inflammation
  • Inflammation: red through inc blood flow
  • Release of prostanoids + bradykinin: lowers pain + heat receptor threshold
29
Q

What happens to the skin after frequent exposure to the sun?

A
  • Age spots: constant trigger + suppression of melanocytes = uneven pigmentation
  • Elastosis: constant change in connective tissue reduce skin strength
30
Q

What is sun protection factor?

A

Multiple by which person can stay in sun w/o burning w/ product compared to time spent in sum w/o burning w/ no product

31
Q

How doe sunscreens minimise the risk of allergy + irritation?

A

Absorb light over broad spectrum at low conc

32
Q

What are chemical sunscreens?

A
  • High energy UV abs by chromophores at specific wavelength + released at lower energy - no chemical change
  • Aromatics conjugated w/ carbonyls
33
Q

What are physical UV filters?

A
  • High refractive index
  • Reflect UV
34
Q

Give examples of physical UV filters

A
  • Titanium dioxide (UV-B)
  • Zinc oxide (UV-A/B)
35
Q

What are film formers?

A

Used to create hardy layer of UV filter on skin:

  • C20-40 alcohols
  • Polyethylene
  • C30-38 olefin
36
Q

What is used to prevent cellular damage by free radicals?

A

Antioxidants:

  • Vit A, C + E
  • Piperidine nitroxide
  • Rutin
  • BHT
37
Q

How do anti-inflammatories help slow the progression of skin damage by UV radiation?

A

Stop biological cascade reaction:

  • Red reddening, pain, blister + peeling
  • However doesn’t stop DNA damage

PHAM02 (35 decks)

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