GED Science Practice 2025 - Free GED Science Practice Questions and Study Guide

A nutrient is defined as any substance that an organism can metabolize to produce energy and support the building of tissues. Nutrients are essential for growth, maintenance, and overall functioning of living organisms. They can be classified into various categories, including macronutrients like carbohydrates, proteins, and fats, which provide the energy and building blocks necessary for bodily functions, as well as micronutrients like vitamins and minerals that play crucial supporting roles in metabolic processes.

In contrast, the other options do not encapsulate this definition as accurately. An organ refers to a specialized structure within an organism made up of tissues that perform specific functions, such as the heart or liver, but does not itself serve as a substance that provides energy or builds tissue. An organic compound is a chemical compound containing carbon and is a broad category that includes nutrients, but it does not specifically refer to substances that organisms can metabolize for energy and tissue-building. An organism, on the other hand, is any individual living entity that can carry out life processes, which includes a wide range of forms, from single-celled bacteria to complex multicellular beings like humans, but it is not a substance itself. Thus, nutrients specifically denote those essential substances involved in energy production and tissue synthesis.