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Most foods contain a mix of some or all of the nutrient classes, together with other substances. Some nutrients can be stored internally (e.g., the fat soluble vitamins), while others are required more or less continuously. Poor health can be caused by a lack of required nutrients or, in extreme cases, too much of a required nutrient.
All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves.
These nutrients are oxidized to produce carbon dioxide and water, and to release chemical energy to drive the organism's metabolism. Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments (cellular respiration in mitochondria ).
The energy provided by macronutrients in food is measured in kilocalories, usually called Calories, where 1 Calorie is the amount of energy required to raise 1 kilogram of water by 1 degree Celsius. [27] Carbohydrates are molecules that store significant amounts of energy. Animals digest and metabolize carbohydrates to obtain this energy.
The sources of energy can be light or chemical compounds; the sources of carbon can be of organic or inorganic origin. [ 1 ] The terms aerobic respiration , anaerobic respiration and fermentation ( substrate-level phosphorylation ) do not refer to primary nutritional groups, but simply reflect the different use of possible electron acceptors in ...
Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. [ 1 ] Most animals derive most of their energy from aerobic respiration , namely combining the carbohydrates , fats , and proteins with oxygen from air or dissolved in water . [ 2 ]
A heterotroph (/ ˈ h ɛ t ər ə ˌ t r oʊ f,-ˌ t r ɒ f /; [1] [2] from Ancient Greek ἕτερος (héteros) 'other' and τροφή (trophḗ) 'nutrition') is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are ...
Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water (green arrow). An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms.