Cells must carry out cellular respiration because it's their primary way of generating energy in the form of ATP (adenosine triphosphate), which is the fuel that powers all cellular processes.

Here's why:

* Energy for Life: Cells are constantly working. They need energy for tasks like building proteins, moving molecules, transporting substances, and maintaining their structure. ATP is the molecule that directly powers these activities.

* Breaking Down Fuel: Cells obtain energy from breaking down fuel sources like glucose (sugar) or fats. Cellular respiration is the process that extracts this energy from those fuel molecules.

* Oxygen Dependence: Many organisms, including humans, rely on oxygen to carry out cellular respiration. Oxygen is a key ingredient in the process, acting as the final electron acceptor in the electron transport chain.

In short, cellular respiration is essential for cells to survive and function because it provides them with the energy they need to carry out all their vital processes.