What are radioactive isotopes and why are they used during photosynthesis?

Answer 1

Oxygen-18 is a natural, stable isotope of oxygen. It is found in the atmosphere and can be found in ice cores to track the temperature over thousands of years as it causes the temperature of the Earth to rise with the higher ratio of 18O compared to 16O. Oxygen 18 was used to give an in sight into photosynthesis as it allows the amount of oxygen taken up during photosynthesis to be measured and showed where the oxygen came from and where it ended up. Scientists firstly added oxygen- 18 to the carbon dioxide and no oxygen- 18 was released, however, when they added oxygen- 18 to the water oxygen- 18 was recorded leaving the plant which shows the oxygen originates from the water. Scientists also discovered that some of the oxygen produced during photosynthesis didn't leave the plant but the majority left the plant through the stomata which is what allowed respiring animals such as Humans to evolve.

Carbon- 14 is a radioactive isotope of carbon, naturally found in the stratosphere and troposphere and is used is radiocarbon dating to date an archaeological, geological and hydrogeological samples. It was used to know what the first products of photosynthesis are and to track the carbon during photosynthesis as it is easy to track in the plant because it is different to the other carbon involved. The experiment began by briefly exposing a green plant to 14CO2 along with light. Straight after this exposure the plant is immersed in boiling water which ceases all biochemical reactions. All the chemical compounds were then extracted and studied to see if they contained carbon- 14. With the brief exposure to carbon- 14 the only compound that contained it was phosphoglyceric acid, a 3 carbon molecule. Scientists have the green plant longer exposure to the isotope and discovered that a variety of compounds contained it, including glucose. With varying lengths of exposure scientists were able to track the sequence from phosphoglyceric acid to glucose. The insight into photosynthesis this gave us was that it showed where the carbon went during photosynthesis and what products were made at the end of this reaction. This investigation was first done by Melvin Calvin and his colleagues.

Answer 2

There are many uses of radioactive isotopes. Two of the most common include carbon dating to discover how old fossils and other historical organic (including carbon) artifacts are and uses of radioactive isotopes in medicine. Radioactive isotopes in medicine are used to help diagnose certain disease states and isolate regions in the body.

Answer 3

Isotope is 2 or more atoms having the same atomic number but different mass numbers. I hope this answers your question my friend.