Provide the full names for the following abbreviations:
$(1)$ $GTP$
$(2)$ $GDP$

(N/A) $(1)$ $GTP$ stands for Guanosine Triphosphate. It is a purine nucleoside triphosphate that serves as an energy source or activator of substrates in metabolic reactions.
$(2)$ $GDP$ stands for Guanosine Diphosphate. It is a nucleoside diphosphate that is formed when $GTP$ loses a phosphate group,often during energy-releasing processes.