Respiration Respiration is the process by which animals take in oxygen necessary for cellular metabolism and release the carbon dioxide that accumulates in their bodies as a result of the expenditure of energy. When an animal breathes, air or water is moved across such respiratory surfaces as the lung or gill in order to help with the process of respiration. Oxygen must be continuously supplied to the animal and carbon dioxide, the waste product, must be continuously removed for cellular metabolism to function properly. For example, if this does not happen and carbon dioxide levels increase in the body, pH levels decrease and the animals may eventually die (see Question: Why is the regulation of body pH important?).
Cellular respiration Cellular respiration (also known as oxidative metabolism) is the set of the metabolic reactions and processes that take place in organisms cells to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions ducoda fields involved in respiration are catabolic reactions that involve the oxidation of one molecule and the reduction of another. Respiration is one of the key ways a cell gains useful energy to fuel cellular reformations. Nutrients commonly used by animal and plant cells in respiration include glucose, amino acids and fatty acids, and a common oxidizing agent (electron acceptor) is molecular oxygen (O2). Bacteria and archaea can also be lithotrophs and these organisms may respire using a broad range of inorganic molecules as electron donors and acceptors, such as sulfur, metal ions, methane or hydrogen. Organisms that use oxygen as a final electron acceptor in respiration are described as aerobic, while those that do not are referred to as anaerobic. The energy released in respiration is used to synthesize ATP to store this energy. The energy stored in ATP can then be used to drive processes requiring energy, including biosynthesis, locomotion or transportation of molecules across cell membranes
Anaerobic respiration biology, anaerobic respiration is a way for an organism to produce usable energy, in the form of adenosine triphosphate, or ATP, without the involvement of oxygen; it is respiration without oxygen. This process is mainly used by prokaryotic organisms (bacteria) that live in environments devoid of oxygen. Although oxygen is not used, the process is still called respiration because the first step of respiration is used, glycolysis. In order for the electron transport chain to function, an exogenous final electron acceptor must be present to take the electron away from the system after it is used. In aerobic organisms, this final electron acceptor is oxygen. Oxygen is a highly electronegative atom and therefore is an excellent candidate for the job. In anaerobes, the chain still functions, but oxygen is not used as the final electron acceptor. Other less electronegative substances such as sulfate (SO4), nitrate (NO3), and sulfur (S) are used. Oftentimes, anaerobic organisms are obligate anaerobes, meaning they can only respire using anaerobic compounds and can actually die in the presence of oxygen Anaerobic respiration is not the same as fermentation, which does not use either the citric acid cycle or the respiratory chain (electron transport chain). In anaerobic respiration, microorganisms are donating electrons to a final electron acceptor, while in fermentation they are essentially creating their own electron acceptor to which they can dump electrons with the purpose of regenerating their NAD+ pool. .
Respiratory system In humans and other animals, for example, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveolar region of the lungs.  Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants also includes anatomical features such as holes on the undersides of leaves known as stomata.
Ecosystem respiration Ecosystem respiration is the sum of all respiration occurring by the living organisms in a specific ecosystem. Ecosystem respiration is typically measured in the natural environment, such as a forest or grassland field, rather than in the laboratory. Ecosystem respiration is the production portion of carbon dioxide in an ecosystems carbon flux, while photosynthesis typically accounts for the majority of the ecosystems carbon consumption.
Plant Respiration Respiration in plants, as in all living organisms, is essential to provide metabolic energy and carbon skeletons for growth and maintenance. As such, respiration is an essential component of a plants carbon budget. Depending on species and environmental conditions, it consumes 25-75% of all the carbohydrates produced in photosynthesis - even more at extremely slow growth rates. Respiration in plants can also proceed in a manner that produces neither metabolic energy nor carbon skeletons, but heat. This type of respiration involves the cyanide-resistant, alternative oxidase; it is unique to plants, and resides in the mitochondria. The activity of this alternative pathway can be measured based on a difference in fractionation of oxygen isotopes between the cytochrome and the alternative oxidase. Heat production is important in some flowers to attract pollinators; however, the alternative oxidase also plays a major role in leaves and roots of most plants. A common thread throughout this volume is to link respiration, including alternative oxidase activity, to plant functioning in different environments.
Animals Respiration In complex animals, where the cells of internal organs are distant from the external environment, respiratory systems facilitate the passage of gases to and from internal tissues. In such systems, when there is a difference in pressure of a particular gas on opposite sides of a membrane, the gas diffuses from the side of greater pressure to the side of lesser pressure, and each gas is transported independently of other gases. For example, in tissues where carbon dioxide concentration is high and oxygen concentration is low as a result of active metabolism, oxygen diffuses into the tissue and carbon dioxide diffuses out. Read more: respiration: Animal Respiration — Infoplease.com http://www.infoplease.com/ce6/sci/A0860708.html#ixzz18BtNM9KO
Aerobic Respiration Aerobic respiration is the release of energy from glucose or another organic substrate in the presence of Oxygen. Strictly speaking aerobic means in air, but it is the Oxygen in the air which is necessary for aerobic respiration. Anaerobic respiration is in the absence of air. Here is a molecular model of a glucose molecule. You do not need to memorise the diagram for you GCSE exam, but it should help you to understand that a molecule of glucose contains six atoms of Carbon (shown in blue), twelve atoms of Hydrogen (shown in green), and six atoms of Oxygen (shown in red).
Glycolysis Glycolysis (from glycose, an older term for glucose + -lysis degradation) is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+. The free energy released in this process is used to form the high-energy compounds ATP (adenosine triphosphate) and NADH ( reduced nicotinamide adenine dinucleotide ). Glycolysis is a definite sequence of ten reactions involving ten intermediate compounds (one of the steps involves two intermediates). The intermediates provide entry points to glycolysis. For example, most monosaccharides, such as fructose, glucose, and galactose, can be converted to one of these intermediates
Photosynthesis Photosynthesis (from the Greek φώτο- [photo-], "light," and σύνθεσις [synthesis], "putting together", "composition") is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can create their own food. In plants, algae, and cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food (the exceptions are chemoautotrophs that live in rocks or around deep sea hydrothermal vents). The rate of energy capture by photosynthesis is immense, approximately 100 terawatts, which is about six times larger than the power consumption of human civilization. As well as energy, photosynthesis is also the source of the carbon in all the organic compounds within organisms bodies. In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year.