Radioactivity

Question 1

Atomic nuclei of unstable isotopes

Answer 1

Can lower their energy state by emitting energy as particles

Question 2

Types of nuclei radiation

Answer 2

Fission particles- alpha radiation
Electrons- beta radiation
Light- Y&X radiation

Question 3

Ejected particles?

Emitting isotope?

Answer 3

Radioactivity

Radioisotope

Question 4

Why are radioisotopes useful to biochemists?

Answer 4

1-Energy of radioactive emissions allows presence of radioisotopes to be detected and measured with great sensitivity
2-Radioisotopes of key-bioelements (C) can be easily produced in nuclear reactors
3-Isotopes share chemical properties (electrons&protons) which makes them interchangeable in biomolecules with their normal non-reactive counterparts

Question 5

The Becquerel

Answer 5

Unit of radioactivity
The radioactivity in a sample is the number of nuclear decays occurring per second DPS
1Bq = 1 DPS

Question 6

The Curie

Answer 6

1 Curie (Ci) is equivalent to the number of disintegration’s in 1g 221Ra in a second

1 Ci = 3.7 x 10(10) Bq

Question 7

Radiation usually falls between

Answer 7

Megabecs and Microcuries

Question 8

Specific activity

Answer 8

Number of Bq compared to the molar amount of radioactive isotope present.

Question 9

Decay over time

Answer 9

The amount a radioisotope decays over time varies but Bq decreases over time is

Question 10

Carbon to nitrogen

Answer 10

Each C14 radioisotope that emits beta radiation (electron) converts to a stable Nitrogen atom
No longer radioactive

Question 11

Measuring rate of decay

Answer 11

Half life (T1/2)
The time taken for half of the radioisotope to decay.

Question 12

Calculating amount of decay

Answer 12

1st half life= Bq=Bqstart x 0.5
2nd half life= Bq=Bqstart x (0.5x0.5)
3rd half life= Bq=Bqstart x (0.5)3

Question 13

Calculating decay prt 2

Answer 13

Calculating Bq at any point after a known Bq start using t1/2 of an isotope

Bq = Bqstart x (0.5)to power of t/(t1/2)

Question 14

Question
18.5MBq at start
23rd to the 31st
1/2 life = 14 days

Answer 14

18.5 x 0.5 to power of (8/14)= 12.4MBq

Question 15

Dangers

Answer 15

Immediate= burns sickness and cataracts

Long term= DNA and germ damage e.g cancer

Question 16

Radiation dose measurement

Answer 16

Sievert (Sv) 
Energy absorbed per mass 
Weighed accordingly to the type of particle 
Units= J/KG
1Sv = 1 J/KG

Question 17

UK average dose
Lethal dose
Human LD50

Answer 17

2.6mSv
»5000mSv
5Sv

Question 18

Allowed as biochemist

Answer 18

Annual whole body= 6-20mSv

Annual to one extremity 150-500mSv

Question 19

Calculating what dose yield received

Answer 19

Point source = amount received per hour per 1 MBq of substance
So at MBq start
MBqstart x Point source = dose received per hour