To determine through which conversion energy is released, let's analyze the options given:
1. ADP to ATP:
- This process is known as phosphorylation, where adenosine diphosphate (ADP) is converted to adenosine triphosphate (ATP). This process requires energy input, typically sourced from cellular respiration or photosynthesis.
2. ATP to ADP:
- This process involves the hydrolysis of ATP (adenosine triphosphate) to ADP (adenosine diphosphate) and an inorganic phosphate (Pi). This conversion releases a significant amount of energy that can be used for various cellular functions.
3. [tex]$NADP ^{+}$[/tex] to NADPH:
- This involves the reduction of nicotinamide adenine dinucleotide phosphate (NADP^+) to NADPH. This transformation typically occurs in the light-dependent reactions of photosynthesis and requires energy input.
4. [tex]$CO_2$[/tex] and [tex]$H_2O$[/tex] to [tex]$C_6H_{12}O_6$[/tex] and [tex]$O_2$[/tex]:
- This represents the equation of photosynthesis, where carbon dioxide and water are converted into glucose (C_6H_{12}O_6) and oxygen. This process requires energy input in the form of light energy.
From these analyses, we determine that the conversion of ATP to ADP releases energy. Hence, the correct choice through which energy is released is:
ATP to ADP
Therefore, the correct answer is:
2
