Given below are two statements. 

Statement I : During oxidation within a cell, all the energy contained in the respiratory substrate is not released freely into the cell.

Statement II : Energy contained in the respiratory substrate is released in a series of slow step-wise reactions controlled by enzymes.

In light of the above statements, choose the correct answer from the options given below. 

Both statements are correct.

Statement I is correct. During cellular respiration, the oxidation of respiratory substrates (such as glucose, fatty acids, and amino acids) involves a stepwise breakdown of these molecules. While the overall energy contained in the substrates is eventually released as ATP and heat, not all of this energy is released at once. Instead, it is released gradually in a controlled manner to efficiently capture and utilize the energy.

Statement II is also correct. The breakdown of respiratory substrates occurs in a series of enzymatic reactions within the cell. These reactions are tightly controlled and regulated by specific enzymes. Each step of the metabolic pathway releases a portion of the energy stored in the substrate, and these stepwise reactions allow the cell to harness the energy more efficiently. Additionally, this controlled release of energy prevents wasteful loss of energy as heat and ensures that the energy can be used to synthesize ATP, which is the primary energy carrier in cells.