"Composition of the human body Body composition may be analyzed in terms of molecular type e.g., water, protein, connective tissue, fats (or lipids), hydroxylapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, muscle, bone, etc. In terms of cell type, the body contains hundreds of different types of cells, but notably, the largest ""number"" of cells contained in a human body (though not the largest mass of cells) are not human cells, but bacteria residing in the normal human gastrointestinal tract. Almost 99% of the"
"human body obtains the majority of its energy through the citric acid cycle, which can use any of the macronutrients to generate adenosine triphosphate (ATP) used to transport chemical energy within cells. The chemical processes involved use energy themselves, so variations in the efficiency of these processes will have the same effect as variations in caloric intake. The human body requires glucose for the brain and nervous system, and a diet that has very few or no dietary carbohydrates forces it to generate this glucose from protein through gluconeogenesis, with an efficiency of approximately 57% (protein and carbohydrate are approximately"
"Glucose is the human body's key source of energy, through aerobic respiration, providing about 3.75 kilocalories (16 kilojoules) of food energy per gram. Breakdown of carbohydrates (e.g., starch) yields mono- and disaccharides, most of which is glucose. Through glycolysis and later in the reactions of the citric acid cycle and oxidative phosphorylation, glucose is oxidized to eventually form carbon dioxide and water, yielding energy mostly in the form of ATP. The insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood. The physiological caloric value of glucose, depending on the source, is 16.2 kilojoules per gram and"
"human biochemical processes by serving structural and functional roles as well as electrolytes. However, as many as twenty-nine elements in total (including hydrogen, carbon, nitrogen and oxygen) are suggested to be used by mammals, as inferred by biochemical and uptake studies. Calcium makes up 920 to 1200 grams of adult body weight, with 99% of it contained in bones and teeth. Phosphorus makes up about 1% of a person's body weight. The other major minerals (potassium, sodium, chlorine, sulfur and magnesium) make up only about 0.85% of the weight of the body. Together these eleven chemical elements (H, C, N,"
"Food energy Food energy is chemical energy that animals (including humans) derive from food through the process of cellular respiration. Cellular respiration may either involve the chemical reaction of food molecules with molecular oxygen (aerobic respiration) or the process of reorganizing the food molecules without additional oxygen (anaerobic respiration). Humans and other animals need a minimum intake of food energy to sustain their metabolism and to drive their muscles. Foods are composed chiefly of carbohydrates, fats, proteins, water, vitamins, and minerals. Carbohydrates, fats, proteins, and water represent virtually all the weight of food, with vitamins and minerals making up only"
"and magnesium. All of the remaining elements in a human body are called ""trace elements"". The trace elements that have a specific biochemical function in the human body are sulfur, iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine and selenium. Most chemical elements that are ingested by organisms are in the form of simple compounds. Plants absorb dissolved elements in soils, which are subsequently ingested by the herbivores and omnivores that eat them, and the elements move up the food chain. Larger organisms may also consume soil (geophagia) or use mineral resources, such as salt licks, to obtain limited minerals"
"g in men, ~2.3 g in women Of the 94 naturally occurring chemical elements, 60 are listed in the table above. Of the remaining 34, it is not known how many occur in the human body. Most of the elements needed for life are relatively common in the Earth's crust. Aluminium, the third most common element in the Earth's crust (after oxygen and silicon), serves no function in living cells, but is harmful in large amounts. Transferrins can bind aluminium. The composition of the human body is expressed in terms of chemicals: The composition of the human body can be"
"fats, and aromatic esters, carotenoids and terpenes. With nitrogen it forms alkaloids, and with the addition of sulfur also it forms antibiotics, amino acids, and rubber products. With the addition of phosphorus to these other elements, it forms DNA and RNA, the chemical-code carriers of life, and adenosine triphosphate (ATP), the most important energy-transfer molecule in all living cells. Nitrogen is the chemical element with atomic number 7, the symbol N and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere. The element"
"diatomic gas with the formula N. Dinitrogen forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere. Many industrially important compounds, such as ammonia, nitric acid,"
"Energy homeostasis In biology, energy homeostasis, or the homeostatic control of energy balance, is a biological process that involves the coordinated homeostatic regulation of food intake (energy inflow) and energy expenditure (energy outflow). The human brain, particularly the hypothalamus, plays a central role in regulating energy homeostasis and generating the sense of hunger by integrating a number of biochemical signals that transmit information about energy balance. Fifty percent of the energy from glucose metabolism is immediately converted to heat. Energy homeostasis is an important aspect of bioenergetics. In the US, biological energy is expressed using the energy unit Calorie with"
"not in an essential biological role. The average adult human body contains approximately atoms and contains at least detectable traces of 60 chemical elements. About 29 of these elements are thought to play an active positive role in life and health in humans. The relative amounts of each element vary by individual, mainly due to differences in the proportion of fat, muscle and bone in their body. Persons with more fat will have a higher proportion of carbon and a lower proportion of most other elements (the proportion of hydrogen will be about the same). The numbers in the table"
"Serum chloride Chloride is an anion in the human body needed for metabolism (the process of turning food into energy). It also helps keep the body's acid-base balance. The amount of serum chloride is carefully controlled by the kidneys. Chloride ions have important physiological roles. For instance, in the central nervous system, the inhibitory action of glycine and some of the action of GABA relies on the entry of Cl into specific neurons. Also, the chloride-bicarbonate exchanger biological transport protein relies on the chloride ion to increase the blood's capacity of carbon dioxide, in the form of the bicarbonate ion;"
"the activation energy. The ""speed"" of a chemical reaction (at given temperature ""T"") is related to the activation energy ""E"", by the Boltzmann's population factor ethat is the probability of molecule to have energy greater than or equal to ""E"" at the given temperature ""T"". This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation.The activation energy necessary for a chemical reaction can be in the form of thermal energy. In biology, energy is an attribute of all biological systems from the biosphere to the smallest living organism. Within an organism it is responsible for"
"same time buildup of argon in the atmosphere has become large enough to be significant. ""For a complete list of the abundance of elements in urban soils, see Abundances of the elements (data page)#Urban soils."" By mass, human cells consist of 65–90% water (HO), and a significant portion of the remainder is composed of carbon-containing organic molecules. Oxygen therefore contributes a majority of a human body's mass, followed by carbon. Almost 99% of the mass of the human body is made up of six elements: hydrogen (H), carbon (C), nitrogen (N), oxygen (O), calcium (Ca), and phosphorus (P). The next"
"growth and development of a biological cell or an organelle of a biological organism. Energy is thus often said to be stored by cells in the structures of molecules of substances such as carbohydrates (including sugars), lipids, and proteins, which release energy when reacted with oxygen in respiration. In human terms, the human equivalent (H-e) (Human energy conversion) indicates, for a given amount of energy expenditure, the relative quantity of energy needed for human metabolism, assuming an average human energy expenditure of 12,500 kJ per day and a basal metabolic rate of 80 watts. For example, if our bodies run"
"or cooler – increase the metabolic rate, thus burning more energy. Prolonged exposure to extremely warm or very cold environments increases the basal metabolic rate (BMR). People who live in these types of settings often have BMRs 5–20% higher than those in other climates. Food energy Food energy is chemical energy that animals (including humans) derive from food through the process of cellular respiration. Cellular respiration may either involve the chemical reaction of food molecules with molecular oxygen (aerobic respiration) or the process of reorganizing the food molecules without additional oxygen (anaerobic respiration). Humans and other animals need a minimum"
"complex carbohydrates and fats, for energy. The first source to which the body turns is glycogen (by glycogenolysis). Glycogen is a complex carbohydrate, 65% of which is stored in skeletal muscles and the remainder in the liver (totaling about 2,000 kcal in the whole body). It is created from the excess of ingested macronutrients, mainly carbohydrates. When glycogen is nearly depleted, the body begins lipolysis, the mobilization and catabolism of fat stores for energy. In this process, fats, obtained from adipose tissue, or fat cells, are broken down into glycerol and fatty acids, which can be used to generate energy."
"elemental composition of the solar system, save for the noted loss of volatile elements to space, and loss of iron which has migrated to the Earth's core. The composition of the human body, by contrast, more closely follows the composition of seawater—save that the human body has additional stores of carbon and nitrogen necessary to form the proteins and nucleic acids, together with phosphorus in the nucleic acids and energy transfer molecule adenosine triphosphate (ATP) that occurs in the cells of all living organisms. Certain kinds of organisms require particular additional elements, for example the magnesium in chlorophyll in green"
"up the four big macromolecules that living organisms need to survive- carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates, made up of carbon, hydrogen, and oxygen, are energy storing molecules. The simplest one of carbohydrates is glucose, CHO, is used in cellular respiration to produce ATP, adenosine triphosphate, which supplies cells with energy. Proteins are chains of amino acids that function to contract skeletal muscle, function catalysts, transport molecules, and storage molecules. Proteins can facilitate biochemical processes, by lowering the activation energy of a reaction. Hemoglobins are also proteins, that carry oxygen to the cells in an organisms body. Lipids, also"
"mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are thought on the basis of good evidence to be necessary for life. All of the mass of the trace elements put together (less than 10 grams for a human body) do not add up to the body mass of magnesium, the least common of the 11 non-trace elements."
"with safe levels of substances such as sugar and oxygen in the blood. The body is studied by health professionals, physiologists, anatomists, and by artists to assist them in their work. The human body is composed of elements including hydrogen, oxygen, carbon, calcium and phosphorus. These elements reside in trillions of cells and non-cellular components of the body. The adult male body is about 60% water for a total water content of some 42 litres. This is made up of about 19 litres of extracellular fluid including about 3.2 litres of blood plasma and about 8.4 litres of interstitial fluid,"
"provide energy: Fat has an energy content of 9kcal/g (~37.7 kJ/g) and proteins and carbohydrates 4kcal/g (~16.7 kJ/g). Micronutrients support metabolism. An essential nutrient is a nutrient required for normal physiological function that cannot be synthesized in the body – either at all or in sufficient quantities – and thus must be obtained from a dietary source. Apart from water, which is universally required for the maintenance of homeostasis in mammals, essential nutrients are indispensable for various cellular metabolic processes and maintaining tissue and organ function. In the case of humans, there are nine amino acids, two fatty acids, thirteen"
"and many others. The biochemical reactions that occur in living organisms are collectively known as metabolism. Among the most important of its mechanisms is the anabolism, in which different DNA and enzyme-controlled processes result in the production of large molecules such as proteins and carbohydrates from smaller units. Bioenergetics studies the sources of energy for such reactions. An important energy source is glucose, which can be produced by plants via photosynthesis or assimilated from food. All organisms use this energy to produce adenosine triphosphate (ATP), which can then be used to energize other reactions. Chemical reactions are central to chemical"
"animals may not (or may need ultra-small amounts). Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus—make up almost 99% of the mass of living cells, including those in the human body (see composition of the human body for a complete list). In addition to the six major elements that compose most of the human body, humans require smaller amounts of possibly 18 more. The four main classes of molecules in biochemistry (often called biomolecules) are carbohydrates, lipids, proteins, and nucleic acids. Many biological molecules are polymers: in this terminology, monomers are relatively small micromolecules that are linked together to"
"much of the animal body (e.g. muscles, skin, and hair). They also form the enzymes that control chemical reactions throughout the body. Each protein molecule is composed of amino acids, which are characterized by inclusion of nitrogen and sometimes sulphur (these components are responsible for the distinctive smell of burning protein, such as the keratin in hair). The body requires amino acids to produce new proteins (protein retention) and to replace damaged proteins (maintenance). As there is no protein or amino acid storage provision, amino acids must be present in the diet. Excess amino acids are discarded, typically in the"
"glucose (CHO) and stearin (CHO) are convenient examples. The food molecules are oxidised to carbon dioxide and water in the mitochondria and some of the energy is used to convert ADP into ATP. The rest of the chemical energy in O and the carbohydrate or fat is converted into heat: the ATP is used as a sort of ""energy currency"", and some of the chemical energy it contains is used for other metabolism when ATP reacts with OH groups and eventually splits into ADP and phosphate (at each stage of a metabolic pathway, some chemical energy is converted into heat)."
"a spark, in a forest fire, or it may be made available more slowly for animal or human metabolism, when these molecules are ingested, and catabolism is triggered by enzyme action. Any living organism relies on an external source of energy – radiant energy from the Sun in the case of green plants, chemical energy in some form in the case of animals – to be able to grow and reproduce. The daily 1500–2000 Calories (6–8 MJ) recommended for a human adult are taken as a combination of oxygen and food molecules, the latter mostly carbohydrates and fats, of which"
"a clinical trial of a pharmaceutical drug. The concept of human-equivalent energy (H-e) assists in understanding of energy flows in physical and biological systems by expressing energy units in human terms: it provides a “feel” for the use of a given amount of energy by expressing it in terms of the relative quantity of energy needed for human metabolism, assuming an average human energy expenditure of 12,500 kJ per day and a basal metabolic rate of 80 watts. A light bulb running at 100 watts is running at 1.25 human equivalents (100/80), i.e. 1.25 H-e. On the other hand, a"
"energy flows in physical and biological systems by expressing energy units in human terms: it provides a ""feel"" for the use of a given amount of energy. Sunlight's radiant energy is also captured by plants as ""chemical potential energy"" in photosynthesis, when carbon dioxide and water (two low-energy compounds) are converted into the high-energy compounds carbohydrates, lipids, and proteins. Plants also release oxygen during photosynthesis, which is utilized by living organisms as an electron acceptor, to release the energy of carbohydrates, lipids, and proteins. Release of the energy stored during photosynthesis as heat or light may be triggered suddenly by"
"Acetylcholine Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals, including humans, as a neurotransmitter—a chemical message released by nerve cells to send signals to other cells [neurons, muscle cells, and gland cells]. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic. Substances that interfere with acetylcholine activity are called anticholinergics. Acetylcholine is the neurotransmitter used at the neuromuscular junction—in other words, it is the chemical that"
"converted to chemical energy in the form of adenosine triphosphate (ATP – a coenzyme) or related compounds, or dissipated as heat. Energy intake is measured by the amount of calories consumed from food and fluids. Energy intake is modulated by hunger, which is primarily regulated by the hypothalamus, and choice, which is determined by the sets of brain structures that are responsible for stimulus control (i.e., operant conditioning and classical conditioning) and cognitive control of eating behavior. Hunger is regulated in part by the action of certain peptide hormones and neuropeptides (e.g., insulin, leptin, ghrelin, and neuropeptide Y, among others)"
"element in the human body by weight, about equal in abundance to potassium, and slightly greater than sodium and chlorine. A human body contains about 140 grams of sulfur. In plants and animals, the amino acids cysteine and methionine contain most of the sulfur, and the element is present in all polypeptides, proteins, and enzymes that contain these amino acids. In humans, methionine is an essential amino acid that must be ingested. However, save for the vitamins biotin and thiamine, cysteine and all sulfur-containing compounds in the human body can be synthesized from methionine. The enzyme sulfite oxidase is needed"
"and about 23 litres of fluid inside cells. The content, acidity and composition of the water inside and outside cells is carefully maintained. The main electrolytes in body water outside cells are sodium and chloride, whereas within cells it is potassium and other phosphates. The body contains trillions of cells, the fundamental unit of life. At maturity, there are roughly 30–37 trillion cells in the body, an estimate arrived at by totalling the cell numbers of all the organs of the body and cell types. The body is also host to about the same number of non-human cells as well"