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What is the difference between direct and indirect effects?
- Direct-Occurs when ionizing radiation interacts directly with vital macromolecules (DNA,RNA) IN VIVO
- Indirect-Occurs when a photon strikes noncritical molecules (WATER) and transfers the energy to target molecules (BOTH CAN HIT THE TARGET CELL)
What happens to the target cell before cell death can occur?
It's target molecule must be inactivated (DNA DOESN'T HAVE TO BE DESTROYED)
What is the basics of target cell theory?
DNA is always the target. Radiation damage to non-abundant molecules necessary for normal cell function could affect the cell severely b/c no similar molecule would be available to replace it.
What are the characteristics of direct and indirect effects?
- Directs-Ionization of DNA
- Indirect-Ionization of water a non-critical molecule
Why are free radicals so damaging and what is it's characteristic?
They are uncharged molecules that contains a single unpaired electron in the outer shell. the are HIGHLY REACTIVE and UNSTABLE. They contain excess energy that can be transferred to other molecules to disrupt bonds and produce point lesions-Radiation hits the cell and knocks out electrons.
What is cross linking?
HAPPENS ONLY AFTER MAIN CHAIN AND IT CONNECTS IN MANY DIFFERENT WAYS. They are macromolecules that have small spur likestructures on sides that attach to similar macromolecules which INCREASES the viscosity of a macromolecule solution.
What is main chain scission?
A breakage in long chain molecules resulting in smaller molecules. It reduces the size and viscosity of the solutions. (ONLY ONE WHERE THE CHAIN BREAKS) (MACROMOLECULES AREN'T DESTROYED BUT TRANSFERRED INTO NEW MOLECULES)
What is point lesion?
OCCURS WHEN CHEMICAL BONDS OF MOLECULES ARE DISRUPTED, BUT DNA STRAND IS NOT BROKEN BUT COULD BE CHANGED. MUTATION MORE CRITICAL.
What are the results of radiation damage to DNA?
- May lead to LATE EFFECTS(DIRECT DAMAGES)
- Loss of cell function
- Affects daughter cells
- can prevent cells from reproducing
- DEATH, CHANGES METABOLIC ACTIVITY, MALIGNANT DISEASE
What is radiolysis?
When water is irradiated it dissociates into other molecular products. Radiation hits hydrogen electrons and kicks it out.
What is the most sensitive macromolecule?
What is the main radiation interaction in the body?
Water-Radiation interacts with water b/c our body is made up of 80% water.
What is LET and does it effect target molecules?
Linear Energy Transfer-The higher the LET the increase chance a master molecule will be directly affected, (BECOMING INACTIVATED)
What kind of radicals can OH* and H* create?
- OH*-Hydrogen Peroxide H2O2
- H*-Hydroperoxyl Radicals
What is the equation that show the formation of damaging products in radiolysis?
- Hydrogen peroxide-H2O2
- Hydroperoxyl Radical-H*+O2=HO2
What is the process of when a water molecule is irradiated?
Loses e- 2ion pairs produced (atom with +or- charge)
What can happen to molecules after going through Cross Linking?
- THEY CAN ATTACH TO OTHER MOLECULES
- OR JOIN TO OTHER BROKEN MOLEUCLES
What is IN VITRO?
Outside the body or cell
What is IN VIVO?
Within the living cell
What is the Law of Bergonie and Tribondeau?
- Predicts cell radiosensitivity
- Different cells respond to radiation differently
- Radiosensitivity is directly proportional to a cell's reproductive activity and inversely proportional to its degree of differentiation.
- Cell's that are most sensitive to radiation are those that reproduce most quickly and immature and have least degree of specialization.
- Cells that are most resistant to radiation are those that reproduce slowly and have high degrees of specialization.
What is the primary cause of cell damage @ low doses?
Point lesion-Changes molecules and causes malfunction with in cell.
What is the process during main chain scission?
Long chain molecules break, NOT DESTROYED BUT TRANSFERRED INTO MOLECULES. Decreases viscosity of fluid in cell.
What are the two main products of radiolysis?
- Hydrogen Peroxide
- Hydroperoxyl Radical