gather and process information from secondary sources to outline the range of isotopes that have been useful in studying photosynthesis and explain how radioactive tracers can be incorporated into plants to follow a biochemical pathway, such as photosynthesis
Background
By “feeding” cells a substance “labeled” with a particular element, that substance can be tracked or traced through the processes in the cell. The chemical behaviour of the radioactive isotope in the labeled substance is the same as in a non-radioactive or “unlabeled” substance. The biochemical or metabolic fate of the radioactively labeled substance can be traced by determining the presence and position of the radioactive atoms. Almost all common small molecules are available in radioactive form.
The range of isotopes useful in studying photosynthesis are:
Isotope Radiation type Half – life Used for the movement of Hydrogen as 3H β 12.1 yearsH+ across the thylakoid membrane
Carbon as 14C
β 5700 yearsC from CO2(g)to glucose
Phosphorous as 32P
β 14.3 daysPi and ADP to form ATP
Oxygen as 18O
None – measured by a mass spectrophotometer
O from H2O compared to CO2