Final answer:
Essential nutrients are substances that the body cannot make on its own and must acquire through diet. These include certain amino acids, fatty acids, vitamins, and minerals. Macronutrients and micronutrients are classifications that refer to the required quantity, not whether a nutrient is essential.
Step-by-step explanation:
Nutrients that cannot be synthesized by the body and are required for normal functioning are known as essential nutrients. These nutrients must be obtained through food because the body is incapable of producing them on its own. While non-essential nutrients can be synthesized by the body and do not need to be obtained directly from the diet, essential nutrients are vital for maintaining health. Examples of essential nutrients include certain amino acids, fatty acids, vitamins, and minerals.
Macronutrients such as carbohydrates, proteins, lipids, and water are required in larger quantities, whereas micronutrients encompass vitamins and minerals needed in smaller amounts. Both macro- and micronutrients can be essential if the body is unable to synthesize them. Vitamin A, for instance, is an essential micronutrient crucial for maintaining connective tissue, and vitamin K is necessary for blood clotting.