Key Stage 3 (KS3) Science – Cells Practice Test 2026 - Free KS3 Science Practice Questions and Study Guide

Cellular respiration is the process by which cells convert glucose and oxygen into usable energy, specifically in the form of adenosine triphosphate (ATP). During this biochemical reaction, glucose—a simple sugar obtained from food—is broken down in the presence of oxygen, resulting in the production of energy, along with byproducts of carbon dioxide and water. This process is essential for the survival of most living organisms, as it provides the energy necessary for cellular functions.

In contrast to the other options, this clearly outlines the primary purpose and outcome of cellular respiration. Photosynthesis, the breakdown of fats, and the synthesis of proteins are different biological processes that serve different functions within living organisms. Each of these mechanisms is crucial, but they do not describe the process of cellular respiration, which specifically pertains to energy production from glucose.