The energy-yielding nutrients are primarily carbohydrates and lipids, while proteins mainly supply the amino acids that are the building blocks of the body itself. Water also helps regulate our internal temperature and cushions, protects, and lubricates joints and many other body structures.
Moreover, water is the largest component of cells, blood, and the fluid between cells, and water makes up about 70 percent of an adult’s body mass. The body’s functional chemicals are dissolved and transported in water, and the chemical reactions of life take place in water. Depending on the environmental temperature and our state of health, we may be able to survive for only a few days without water. The three basic classes of nutrients are water, the energy-yielding and body-building nutrients, and the micronutrients (vitamins and minerals). NutrientsĪ nutrient is a substance in foods and beverages that is essential to human survival. Brain damage is likely within five minutes without oxygen, and death is likely within ten minutes. Brain cells are especially sensitive to lack of oxygen because of their requirement for a high-and-steady production of ATP. OxygenĪtmospheric air is only about 20 percent oxygen, but that oxygen is a key component of the chemical reactions that keep the body alive, including the reactions that produce ATP. The next sections explore these four requirements of life. Although you may rarely think about it, you also cannot live outside of a certain range of temperature and pressure that the surface of our planet and its atmosphere provides. Earth and its atmosphere have provided us with air to breathe, water to drink, and food to eat, but these are not the only requirements for survival. Humans have been adapting to life on Earth for at least the past 200,000 years.
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