Brown adipose tissue (BAT) or brown fat is one of the two types of adipose tissue (the other being white adipose tissue) that is present in many newborn or hibernating mammals. Its primary purpose is to generate body heat. In contrast to white adipocytes (fat cells), which contain a single, large fat vacuole, brown adipocytes contain several smaller vacuoles and a much higher number of mitochondria. Brown fat also contains more capillaries since it has a greater need for oxygen than most tissues. It has been suggested that Subcutaneous fat be merged into this article or section. ... White adipose tissue (WAT) or white fat is one of the two types of adipose tissue found in mammals (compare to brown adipose tissue). ... This article refers to the process of hibernation in biology. ... Adipose tissue is an anatomical term for loose connective tissue composed of energy in the form of fat, although it also cushions and insulates the body. ... Schematic of typical animal cell, showing subcellular components. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... The word capillary is used to describe any very narrow tube or channel through which a fluid can pass. ...

Biochemistry

The mitochondria in a eukaryotic cell utilize fuels to produce energy (in the form of ATP). This process involves storing energy as a proton gradient, also known as the proton motive force (PMF), across the mitochondrial inner membrane. This energy is used to synthesise ATP when the protons flow across the membrane (down their concentration gradient) through the ATP synthase enzyme, this is known as chemiosmosis. Kingdoms Animalia - Animals Fungi Plantae - Plants Protista Alternative Phylogeny Unikonta    Opisthokonta    Amoebozoa Bikonta    Apusozoa    Cabozoa       Rhizaria       Excavata    Corticata       Archaeplastida       Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms with a complex cell or cells, where the genetic material is organized into a membrane-bound nucleus or nuclei. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Electrochemical gradients in cellular biology refers to the electrical and chemical properties across a membrane. ... An ATP synthase (EC 3. ... Chemiosmosis is the diffusion of ions across a membrane. ...

In endothermic animals, body heat is maintained by signalling the mitochondria to allow protons to run back along the gradient without producing ATP. This can occur since an alternative return route for the protons exists through an uncoupling protein in the inner membrane. This protein, known as uncoupling protein 1, facilitates the return of the protons after they have been actively pumped out of the mitochondria by the electron transport chain. This alternative route for protons uncouples oxidative phosphorylation and the energy in the PMF is released as heat. A warm-blooded (homeothermic) animal is one that can keep its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis) . This can involve not only the ability to generate heat, but also the ability to cool down... The Electron Transport Chain. ... The Electron Transport Chain. ...

To some degree all cells of endotherms give off heat, especially when body temperature is below a regulatory threshold, however, brown adipose tissue is highly specialized for this non-shivering thermogenesis. Firstly, each cell has a higher number of mitochondria compared to more typical cells. Secondly, these mitochondria have a higher than normal concentration of thermogenin in the inner membrane. Thermogenesis is the process of heat production in organisms. ...

Function in babies

In neonates (new born babies), brown fat, which then makes up about 5% of the body mass and is located on the back, along the upper half of the spine and towards the shoulders, is of great importance to avoid lethal cold (hypothermia is a major death risk for premature neonates). Numerous factors make infants more susceptible to cold than adults: A human infant The word Infant derives from the Latin in-fans, meaning unable to speak. ... Hypothermia refers to any condition in which the temperature of a body drops below the level required for normal metabolism and/or bodily function to take place. ...

• The higher ratio of body surface (proportional to heat loss) to body volume (proportional to heat production)
• The higher proportional surface area of the head
• The low amount of musculature and the inability or reluctance to shiver
• A lack of thermal insulation, e.g. subcutaneous fat and fine body hair (especially in prematurely born children)
• The inability to move away from cold areas, air currents or heat-draining materials
• The inability to use additional ways of keeping warm (e.g. turning up a heater, drying their skin, changing clothes or performing physical exercise)
• The nervous system is not fully developed and does not respond quickly and/or properly to cold (e.g. by contracting blood vessels in the skin)

However, the burning of the brown fat will, in fact, provide a baby with an alternative form of heat induction. This form is an adequate substitute to any and all other unconscious means of an adult. Shivering is a human bodily function in response to cold. ...

When growing up, most of the mitochondria (which are responsible for the brown color) in brown fat disappear, and the tissue becomes similar in function and appearance to white fat, as a mere fat deposit, though some adults do retain their brown fat.

External links

• Histology at BU 04901lob - "Connective Tissue: multilocular (brown) adipocytes"

This article may require cleanup to meet Wikipedia's quality standards. Please discuss this issue on the talk page or replace this tag with a more specific message. This article has been tagged since June 2007.

Brwon adipose tissue was supposed to disappear in adult humans but recent studies using PET scanning have shown that it is still present in many adults in the upper chest and neck. It becomes more visible (Increasing tracer uptake) with cold exposure and it is blocked by adrenergic beta blocker given before the scan. For similarly-named academic institutions, see Boston (disambiguation). ... Image File history File links Broom_icon. ...