What help the body change food into energy and repair and replace old and damaged parts?

The body uses enzymes, hormones, and various biochemical pathways to convert food into energy. Enzymes break down macronutrients—carbohydrates, proteins, and fats—into smaller molecules that can be absorbed and utilized. Hormones regulate metabolism and energy production, while cellular processes like cellular respiration and protein synthesis help repair and replace old or damaged tissues. Together, these systems ensure that the body efficiently transforms nutrients into energy and maintains its structural integrity.