Radioactive isotopes (Few quick questions)

[scilearner]

Hello everyone,

 

(These questions seem long but the answers are very short. So please read)

 

I'm going to start biology next year. I was just reading the first chapter of my biology book. I'm finding radioactive isotopes bit hard. These are 3 quick questions in the textbook. These might be very easy, but I'm very new to biology. Your help would be very greatly appreciated. Thank you

 

1. The Chernobyl disaster involved radioisotope that takes a long time to decay. This is why it created problems for generations to come. If you were choosing a radioisotope to use in medical diagnosis would you choose one with a slow or fast decay?

 

My guess is fast. Less problems

 

2. A farmer was offered three types of fertiliser to use on his crop. Explain how isotope labels such as nitrogen-15 and phosphorus-32 could be used to determine the optimum fertiliser for his crop.

 

3. Radioisotopes are used to treat cancerous growths. How would they exert their effect on a tumour.

 

My guess tumour cells can be killed by the radiation of radioisotopes

 

I want to understand the answer so please post an explanation. Thank you very much!!

[insane_alien]

well, your off to a good start, the two questions you took a guess at are more or less right.

 

for 1/ it is most certainly fast as this lowers the risk of the radiation causing damage to the body. not something you want. shortlived ones require less of a dose due to their higher activity and don't leave you radioactive for years to come.

 

2/ have a guess at this one. to give you a hint, what needs to happen to fertilizers before they can affect the growth of a plant?

 

3/ yes, radiation does kill cancer cells, the only problem is that they kill cells indiscriminately so you need to kill the tumour faster than the stuff around it. if you look on wikipedia for radiotherapy you will find a lot of information on how this is done. The radio isotopes emit gamma radiation and stay outside the body.

[swansont]

For #1 you need to realize that there is also the residence time in the body, known as the biological half-life. A long-lived isotope isn't the same problem of the body excretes it quickly, and if the radioactive half-life is too short, there are issues in obtaining the isotope in the first place, or storing it. A few hour half-life might seem ideal for tests, but if you can't make it on-site, it's probably not going to be feasible.

[YT2095]

actualy, it`s not usualy made on site, but ordered in. they work to a Very critical time constraint also, if you`re late you PAY big time! and the stuff is scrapped. also the room is evacuated leaving you alone with only your isotope for company, and you also have to stay there for some time after, the room isn`t entered at all by staff for some time much later also, esp in the case of radioactive Gasses used for Lung imaging, and you Cough or make or mistake then YOU PAY again!

[scilearner]

Thank you very much for the help everyone. Really appreciate your time and effort to answer these questions.

 

@Insane Alien: Thank you very much for the answers. I still can't figure out the

second question. Well fertilisers should be added to the soil

before they can affect the growth of a plant. I still don't fully

understand this question.

[insane_alien]

okay, what happens to the fertilizer after its added to the soil?

[scilearner]

okay, what happens to the fertilizer after its added to the soil?

 

The ferilizer decays. Oh do the labels show the decaying rate

[layzwombat]

Plants use a ratio of C:N:P and I actually forget the ratio at the moment (not important to answer), but you can use the isotopes to measure which fertilizer would closest match your crop ratio. An example of this would be if you were growing soy beans, your fertilizer should probably have zero nitrogen since legumes fix their own nitrogen, and thus you can lower your environmental damage.

[insane_alien]

yes the radio isotopes will be decaying all the time, but how soe it help the plants grow (assume a non radioactive fertiliser for this part)

[scilearner]

yes the radio isotopes will be decaying all the time, but how soe it help the plants grow (assume a non radioactive fertiliser for this part)

 

A fertilizer is added to soil to improve plants' growth and yield. Fertilizers provide nutrients that are responsible for growth and reproduction of plants.

[insane_alien]

okay, you seem to have a mental block on this part so i'm going to give you a bit more help than normal.

 

The nutrients in the fertiliser need to be absorbed by the plants first before they affect the growth of the plant. If you added nitrate and phosphate fertilisers in equal amounts(wrt mol) how could you tell which one the plant absorbs more of?

[scilearner]

I certainly have a mental block with this question. I'm not really sure about the answer. It should depend on the plant and the end results. I'm not really sure

[YT2095]

actualy, IIRC it`s by detecting the Nitrogen isotopes that we can work out which animals were meat or plant eaters also.

[swansont]

I certainly have a mental block with this question. I'm not really sure about the answer. It should depend on the plant and the end results. I'm not really sure

 

What end result would you want to measure?

[scilearner]

What end result would you want to measure?

 

Fruits, growth. I'm not really sure. Just explain the answer please