National League for Nursing (NLN PAX) Exam 2026 – 400 Free Practice Questions to Pass the Exam

Energy transfer in cellular processes primarily occurs through ATP, or adenosine triphosphate. ATP is often referred to as the "energy currency" of the cell because it captures and transfers chemical energy within cells. When cellular processes require energy for activities such as muscle contraction, active transport across membranes, or biochemical reactions, ATP donates a phosphate group to other molecules in a process known as phosphorylation. This transfer of the phosphate group releases energy, which can then be harnessed for various cellular functions.

While glucose is an important energy source, it is ultimately broken down during cellular respiration to produce ATP, rather than serving as a direct means of energy transfer in cellular processes. Water plays critical roles in cellular metabolism, such as participating in chemical reactions, but it does not function as a direct energy carrier. Proteins are essential in many processes, including catalysis and transport, but they do not serve primarily to transfer energy in the same way that ATP does.