Radiation and its Biological Effects

Question 1

What are the 3 types of radiation?

Answer 1

• Alpha particles
• Beta particles
• Gamma rays

Question 2

What are alpha particles made up of?

Answer 2

2 protons and 2 neutrons

Question 3

How ionizing are alpha particles?

Answer 3

Highly ionizing

Question 4

How great is the penetration of alpha particles?

Answer 4

They have very low penetration

Question 5

What usually produces alpha particles?

Answer 5

The alpha decay of large nuclei of heavy elements

Question 6

How harmful are alpha particles?

Answer 6

Very harmful if ingested, not very harmful if source is outside the body

Question 7

How does a Geiger counter work?

Answer 7

• When hit by a high energy particle the Ar molecules are stripped of electrons and ionized
• This produces a current which is amplified

Question 8

When alpha decay occurs what can also be given off?

Answer 8

Gamma radiation

Question 9

What particle is a beta particle?

Answer 9

A high speed electron

Question 10

How ionizing are beta particles?

Answer 10

Less ionizing than alpha particles but still ionizing

Question 11

Compare how penetrative alpha and beta particles are

Answer 11

Beta particles are more penetrative then alpha particles

Question 12

When are beta particles produced?

Answer 12

When a neutron is converted to a proton

Question 13

What can also be produced when a proton converts to a neutron?

Answer 13

A positron and an antineutrino

Question 14

When are gamma rays produced?

Answer 14

When a nucleus that has undergone alpha or beta decay is left in a higher energy state, then returns to its ground state

Question 15

Do gamma rays have mass?

Answer 15

No

Question 16

How penetrative are gamma rays?

Answer 16

Higly penetrative

Question 17

What is the ionization potential for gamma rays?

Answer 17

Low

Question 18

What are gamma rays used for?

Answer 18

Radiotherapy

Question 19

What are the 2 sources of neutrons?

Answer 19

• Nuclear reactors
• Nuclear spallation sources

Question 20

Can neutrons penetrate biological material?

Answer 20

Yes, with limited damage

Question 21

What is neutron scattering used for?

Answer 21

To determine low-resolution molecular shapes of protein complexes in solution

Question 22

What are the 3 ways radiation can be detected?

Answer 22

• Geiger counter
• Liquid scintillation
• Autoradiography

Question 23

What is neutron crystallography used to visualise?

Answer 23

H atoms

Question 24

Give an advantage of neutron crystallography over X-ray crystallography

Answer 24

X-ray crystallography cannot show H bonds whilst Neutron crystallography can

Question 25

How does a scintillation counter work?

Answer 25

* Radiation produces fluorescence in the scintillant * This light then converted to am electrical signal, amplified, and counted

Question 26

What is the advantage of autoradiography?

Answer 26

It can be used to measure very weak samples

Question 27

Name a useful technique autoradiography can be paired with

Answer 27

Densitometry

Question 28

Explain how autoradiography and densiometry can be combined

Answer 28

* An autoradiograph is completed * The density of the bands can be measured in order to quantify the results

Question 29

What are the problems with combining autoradiography with densiometry?

Answer 29

* the longer the exposure, the darker the band gets and the more difficult it is to distinguish * Inherent error due to fuzziness of bands

Question 30

What are the 4 most common radioisotopes used in biochemistry?

Answer 30

* ³H * ¹⁴C * ³²P * ¹²⁵I

Question 31

How can isotopes be used to analyse chemical reactions?

Answer 31

* Monitoring transfer of atoms * Kinetic isotope effect

Question 32

What is the kinetic isotope effect?

Answer 32

* Replacement of H with deuterium decreased X-H vibrational frequency * Can be used to deduce if breaking X-H bond is rate determing step (if reaction rate is reduced)

Question 33

The interaction of radiation with which molecule produces most of the harmful effects radiation has on biological systems?

Answer 33

Water

Question 34

Which especially harmful species can irradiation of water produce?

Answer 34

OH•

Question 35

Give 4 types of lesions which are found on DNA

Answer 35

* Rupture of strands * Alteration to bases * Destruction of sugars * Crosslinks and formation of dimers

Question 36

What is the most common cause of single strand DNA breaks?

Answer 36

OH•

Question 37

Which bases are more sensitive to radiation?

Answer 37

Pyrimidines (T, C)

Question 38

Which enzyme is responsible for removing faulty bases from DNA?

Answer 38

DNA glycosylase

Question 39

What happens in base excision repair?

Answer 39

* Faulty base is removed by DNA glycosylase * Endonuclease opens DNA strand * DNA polymerase inserts new base * DNA ligase re-connects strand

Question 40

How are double strand DNA breaks repaired?

Answer 40

Via homologous recombination mechanisms

Question 41

Why are radioisotopes extremely useful for investigation of biological systems?

Answer 41

* Readily incorporated * Very high sensitivity * Can be used to trace pathways and understand chemical reactions

Question 42

What is translesion synthesis?

Answer 42

A repair mechanism for crosslinked DNA which uses specialised DNA polymerases