Nutrient
From Wikipedia, the free encyclopedia
A nutrient is either a chemical element or compound used in an organism's metabolism or physiology. Six nutrient groups exist and are broadly classified into those providing energy, and those used as components in the body or cellular structures.[citation needed] A nutrient is essential to an organism if it cannot be synthesized in the organism and must be obtained from a food source.
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[edit] Substances that provide energy
- Carbohydrates are compounds made up of sugars. Carbohydrates are classified by their number of sugar units: monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).
- Proteins are organic compounds that consists of the amino acids joined by peptide bonds. The body cannot manufacture some of the amino acids (termed essential amino acids); the diet must supply these. In nutrition, proteins are broken down through digestion back into free amino acids.
- Fats consist of a glycerin molecule with three fatty acids attached. Fatty acids are unbranched hydrocarbon chains, connected by single bonds alone (saturated fatty acids) or by both double and single bonds (unsaturated fatty acids). Fats are needed to keep cell membranes functioning properly, to insulate body organs against shock, to keep body temperature stable, and to maintain healthy skin and hair. The body does not manufacture certain fatty acids (termed essential fatty acids) and the diet must supply these.
Fat has an energy content of 9 kcal/g (~37.7 kJ/g); proteins and carbohydrates 4 kcal/g (~16.7 kJ/g). Ethanol (grain alcohol) has an energy content of 7 kcal/g (~29.3 kJ/g).[citation needed]
[edit] Substances that support metabolism
- Minerals are generally trace elements, salts, or ions such as copper and iron. These minerals are essential to human metabolism.
- Vitamins are organic compounds essential to the body. They usually act as coenzymes or cofactors for various proteins in the body.
- Water is an essential nutrient and is the solvent in which all the chemical reactions of life take place.
[edit] Nutrition as a science
Any classification of "nutrients" is likely to be arbitrary given the status of nutrition as a developing science. Researchers are becoming more aware of a wider range of nutrients essential for health.
Organisms can metabolise organic compounds to use for their energy content, for structural purposes (growth or replacement of living structures), or for participation in chemical reactions necessary for life.
The discovery of the group of nutrients called phytonutrients reinforces the provisional nature of our knowledge. We know little about phytonutrients - organic compounds from plants - which play an essential role in the normal functioning of a body and have complex hormonal effects on health or play an active role in the amelioration of disease.[citation needed]
Nutrient Sorted Alphabetically Sorted by Nutrient Content Moisture Protein Fat Energy (Calories) Carbohydrate (by difference) Total dietary fiber Calcium Iron Magnesium Phosphorus Potassium Sodium Zinc Copper Manganese Selenium Vitamin A Vitamin E Vitamin C Thiamin Riboflavin Niacin Pantothenic acid Vitamin B-6 Vitamin B-12 Dietary Folate Equivalents Cholesterol Total saturated fatty acids Total monounsaturated fatty acids Total polyunsaturated fatty acids
[edit] Nutrients and the environment
While in essence true to the definition above, the term weed has a more limited meaning within the specialised fields of quality and water pollution, referring specifically to plant fertilizers. In this context, certain mineral compounds can have an adverse impact on water quality because of their ability to promote excessive plant and algae growth. This process is called eutrophication. An excessive growth of aquatic plants can clog waterways (see giant salvinia for example), and over-stimulation of algae and microbes can lead to an algal bloom and oxygen depletion.
Only a small number of elements are involved in this process: nitrogen and phosphorus in most aquatic systems. Mineral compounds involved are ammonia, nitrites, nitrates, and orthophosphates. Organic compounds also may contribute, since they also contain nitrogen and phosphorus. This is a result of plants being made up mostly of compounds of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P), and lesser amounts of sulfur (S), potassium (K), magnesium (Mg), and calcium (Ca). These elements constitute the macronutrients.[citation needed] Many other elements, though necessary for growth, classify as micronutrients due to the very small quantities required.
Plants obtain carbon, hydrogen, and oxygen (elements most needed for growth) from the air and water, where all three elements occur in great abundance as water and as carbon dioxide. Nutrients having greatest potential to influence plant growth in aquatic environments is those elements needed for plant growth in proportionately large amounts (that is, macronutrients) but likely to become limiting—that is, present in amounts that could be depleted by continued growth. Once used up, further growth will not be possible. Of the nine macronutrients, nitrogen and phosphorus are most likely to become limiting. The others always remain present in great abundance (C, H, O) or usually in amounts that exceed the requirements of aquatic plants or algae.
Farmers apply fertilizer nutrients in the form of nitrogen, phosphorus, and potassium (N, P, and K with perhaps micronutrients) to prevent these elements from becoming limiting in the soil. These elements become concentrated in wastewaters from animal pens and septic or sewage systems. And these elements (especially N and P) in runoff or wastewater discharges reaching streams, lakes, or seas will promote aquatic plant growth. Abundant plant growth itself gives cause for concern in assessing water quality. The most abundant "plants" in most aquatic environments are algae, When essential nutrients are plentiful, algae multiply. If these algae are microscopic phytoplankton, their growth increases the turbidity of the water. The water then becomes cloudy, colored a shade of green, yellow, or brown (sometimes red; see algal bloom). A super abundance of algae, or of higher plants, in an aquatic system can signal excessive inputs of nutrients.
[edit] References
- Donatelle, Rebecca J. Health: The Basic"
[edit] See also
- Ecological sanitation
- Essential fatty acids
- Essential nutrient
- Nutrient density
- Omega-3 fatty acids
- Omega-6 fatty acids
