Final answer:
The statement is true as both ATP and Pcr serve as immediate energy sources for cells, with ATP being the main energy currency and Pcr acting as a quick phosphate donor to regenerate ATP.
Step-by-step explanation:
The assertation that both ATP (Adenosine triphosphate) and Pcr (Phosphocreatine) are immediate sources of energy used by the cells is true. ATP is known as the 'energy currency' of the cell, as it stores energy in its phosphate ester bonds. This energy is released when ATP is converted into ADP (Adenosine diphosphate) and a phosphate group. Pcr, on the other hand, acts as a reserve of high-energy phosphates in muscle cells and is used to quickly regenerate ATP from ADP, thereby providing a rapid source of energy. Both compounds play a pivotal role in the supply of energy for cellular processes, including muscle contractions and active transport.
For example, during muscle contraction, the ATP already present in muscle cells is used first, after which more ATP is generated from Pcr. Moreover, primary active transport explicitly relies on energy from ATP, while secondary active transport makes use of the gradient created by primary active transport, which indirectly depends on ATP's energy transformation abilities.