Bioenergetics

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Bioenergetics is a field in biochemistry and cell biology that concerns energy flow through living systems. [1] This is an active area of biological research that includes the study of the transformation of energy in living organisms and the study of thousands of different cellular processes such as cellular respiration and the many other metabolic and enzymatic processes that lead to production and utilization of energy in forms such as adenosine triphosphate (ATP) molecules. [2] [3] That is, the goal of bioenergetics is to describe how living organisms acquire and transform energy in order to perform biological work. [4] The study of metabolic pathways is thus essential to bioenergetics.

Contents

Overview

Bioenergetics is the part of biochemistry concerned with the energy involved in making and breaking of chemical bonds in the molecules found in biological organisms. [5] It can also be defined as the study of energy relationships and energy transformations and transductions in living organisms. [6] The ability to harness energy from a variety of metabolic pathways is a property of all living organisms. Growth, development, anabolism and catabolism are some of the central processes in the study of biological organisms, because the role of energy is fundamental to such biological processes. [7] Life is dependent on energy transformations; living organisms survive because of exchange of energy between living tissues/ cells and the outside environment. Some organisms, such as autotrophs, can acquire energy from sunlight (through photosynthesis) without needing to consume nutrients and break them down. [8] Other organisms, like heterotrophs, must intake nutrients from food to be able to sustain energy by breaking down chemical bonds in nutrients during metabolic processes such as glycolysis and the citric acid cycle. Importantly, as a direct consequence of the First Law of Thermodynamics, autotrophs and heterotrophs participate in a universal metabolic network—by eating autotrophs (plants), heterotrophs harness energy that was initially transformed by the plants during photosynthesis. [9]

In a living organism, chemical bonds are broken and made as part of the exchange and transformation of energy. Energy is available for work (such as mechanical work) or for other processes (such as chemical synthesis and anabolic processes in growth), when weak bonds are broken and stronger bonds are made. The production of stronger bonds allows release of usable energy.

Adenosine triphosphate (ATP) is the main "energy currency" for organisms; the goal of metabolic and catabolic processes are to synthesize ATP from available starting materials (from the environment), and to break- down ATP (into adenosine diphosphate (ADP) and inorganic phosphate) by utilizing it in biological processes. [4] In a cell, the ratio of ATP to ADP concentrations is known as the "energy charge" of the cell. A cell can use this energy charge to relay information about cellular needs; if there is more ATP than ADP available, the cell can use ATP to do work, but if there is more ADP than ATP available, the cell must synthesize ATP via oxidative phosphorylation. [5]

Living organisms produce ATP from energy sources via oxidative phosphorylation. The terminal phosphate bonds of ATP are relatively weak compared with the stronger bonds formed when ATP is hydrolyzed (broken down by water) to adenosine diphosphate and inorganic phosphate. Here it is the thermodynamically favorable free energy of hydrolysis that results in energy release; the phosphoanhydride bond between the terminal phosphate group and the rest of the ATP molecule does not itself contain this energy. [10] An organism's stockpile of ATP is used as a battery to store energy in cells. [11] Utilization of chemical energy from such molecular bond rearrangement powers biological processes in every biological organism.

Living organisms obtain energy from organic and inorganic materials; i.e. ATP can be synthesized from a variety of biochemical precursors. For example, lithotrophs can oxidize minerals such as nitrates or forms of sulfur, such as elemental sulfur, sulfites, and hydrogen sulfide to produce ATP. In photosynthesis, autotrophs produce ATP using light energy, whereas heterotrophs must consume organic compounds, mostly including carbohydrates, fats, and proteins. The amount of energy actually obtained by the organism is lower than the amount present in the food; there are losses in digestion, metabolism, and thermogenesis. [12]

Environmental materials that an organism intakes are generally combined with oxygen to release energy, although some nutrients can also be oxidized anaerobically by various organisms. The utilization of these materials is a form of slow combustion because the nutrients are reacted with oxygen (the materials are oxidized slowly enough that the organisms do not produce fire). The oxidation releases energy, which may evolve as heat or be used by the organism for other purposes, such as breaking chemical bonds.

Types of reactions

The free energy (ΔG) gained or lost in a reaction can be calculated as follows: ΔG = ΔH − TΔS where ∆G = Gibbs free energy, ∆H = enthalpy, T = temperature (in kelvins), and ∆S = entropy. [15]

Examples of major bioenergetic processes

Additional information

Reaction coupling

Is the linkage of chemical reactions in a way that the product of one reaction becomes the substrate of another reaction.

Cotransport

In August 1960, Robert K. Crane presented for the first time his discovery of the sodium-glucose cotransport as the mechanism for intestinal glucose absorption. [24] Crane's discovery of cotransport was the first ever proposal of flux coupling in biology and was the most important event concerning carbohydrate absorption in the 20th century. [25] [26]

Chemiosmotic theory

One of the major triumphs of bioenergetics is Peter D. Mitchell's chemiosmotic theory of how protons in aqueous solution function in the production of ATP in cell organelles such as mitochondria. [27] This work earned Mitchell the 1978 Nobel Prize for Chemistry. Other cellular sources of ATP such as glycolysis were understood first, but such processes for direct coupling of enzyme activity to ATP production are not the major source of useful chemical energy in most cells. Chemiosmotic coupling is the major energy producing process in most cells, being utilized in chloroplasts and several single celled organisms in addition to mitochondria.

Binding Change Mechanism

The binding change mechanism, proposed by Paul Boyer and John E. Walker, who were awarded the Nobel Prize in Chemistry in 1997, suggests that ATP synthesis is linked to a conformational change in ATP synthase. This change is triggered by the rotation of the gamma subunit. [28] ATP synthesis can be achieved through several mechanisms. The first mechanism postulates that the free energy of the proton gradient is utilized to alter the conformation of polypeptide molecules in the ATP synthesis active centers. [29] The second mechanism suggests that the change in the conformational state is also produced by the transformation of mechanical energy into chemical energy using biological mechanoemission. [30]

Energy balance

Energy homeostasis is the homeostatic control of energy balance  – the difference between energy obtained through food consumption and energy expenditure – in living systems. [31] [32]

See also

Related Research Articles

<span class="mw-page-title-main">Biochemistry</span> Study of chemical processes in living organisms

Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, and metabolism. Over the last decades of the 20th century, biochemistry has become successful at explaining living processes through these three disciplines. Almost all areas of the life sciences are being uncovered and developed through biochemical methodology and research. Biochemistry focuses on understanding the chemical basis which allows biological molecules to give rise to the processes that occur within living cells and between cells, in turn relating greatly to the understanding of tissues and organs as well as organism structure and function. Biochemistry is closely related to molecular biology, the study of the molecular mechanisms of biological phenomena.

<span class="mw-page-title-main">Citric acid cycle</span> Interconnected biochemical reactions releasing energy

The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of biochemical reactions to release the energy stored in nutrients through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The chemical energy released is available under the form of ATP. The Krebs cycle is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism. Even though it is branded as a "cycle", it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized.

<span class="mw-page-title-main">Glycolysis</span> Series of interconnected biochemical reactions

Glycolysis is the metabolic pathway that converts glucose into pyruvate and, in most organisms, occurs in the liquid part of cells. The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). Glycolysis is a sequence of ten reactions catalyzed by enzymes.

<span class="mw-page-title-main">Metabolism</span> Set of chemical reactions in organisms

Metabolism is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks of proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transportation of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism.

<span class="mw-page-title-main">Metabolic pathway</span> Linked series of chemical reactions occurring within a cell

In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reactions catalyzed by enzymes. In most cases of a metabolic pathway, the product of one enzyme acts as the substrate for the next. However, side products are considered waste and removed from the cell.

<span class="mw-page-title-main">Adenosine diphosphate</span> Chemical compound

Adenosine diphosphate (ADP), also known as adenosine pyrophosphate (APP), is an important organic compound in metabolism and is essential to the flow of energy in living cells. ADP consists of three important structural components: a sugar backbone attached to adenine and two phosphate groups bonded to the 5 carbon atom of ribose. The diphosphate group of ADP is attached to the 5’ carbon of the sugar backbone, while the adenine attaches to the 1’ carbon.

<span class="mw-page-title-main">Cellular respiration</span> Process to convert glucose to ATP in cells

Cellular respiration is the process by which biological fuels are oxidized in the presence of an inorganic electron acceptor, such as oxygen, to drive the bulk production of adenosine triphosphate (ATP), which contains energy. Cellular respiration may be described as a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from nutrients into ATP, and then release waste products.

Anaerobic glycolysis is the transformation of glucose to lactate when limited amounts of oxygen (O2) are available. This occurs in health as in exercising and in disease as in sepsis and hemorrhagic shock. Anaerobic glycolysis is an effective means of energy production only during short, intense exercise, providing energy for a period ranging from 10 seconds to 2 minutes. This is much faster than aerobic metabolism. The anaerobic glycolysis (lactic acid) system is dominant from about 10–30 seconds during a maximal effort. It replenishes very quickly over this period and produces 2 ATP molecules per glucose molecule, or about 5% of glucose's energy potential (38 ATP molecules). The speed at which ATP is produced is about 100 times that of oxidative phosphorylation.

<span class="mw-page-title-main">Anabolism</span> Metabolic pathways to build molecules

Anabolism is the set of metabolic pathways that construct macromolecules like DNA or RNA from smaller units. These reactions require energy, known also as an endergonic process. Anabolism is the building-up aspect of metabolism, whereas catabolism is the breaking-down aspect. Anabolism is usually synonymous with biosynthesis.

Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms.

<span class="mw-page-title-main">Glyceraldehyde 3-phosphate</span> Chemical compound

Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a metabolite that occurs as an intermediate in several central pathways of all organisms. With the chemical formula H(O)CCH(OH)CH2OPO32-, this anion is a monophosphate ester of glyceraldehyde.

<span class="mw-page-title-main">Cori cycle</span> Series of interconnected biochemical reactions

The Cori cycle, named after its discoverers, Carl Ferdinand Cori and Gerty Cori, is a metabolic pathway in which lactate, produced by anaerobic glycolysis in muscles, is transported to the liver and converted to glucose, which then returns to the muscles and is cyclically metabolized back to lactate.

In biochemistry, steady state refers to the maintenance of constant internal concentrations of molecules and ions in the cells and organs of living systems. Living organisms remain at a dynamic steady state where their internal composition at both cellular and gross levels are relatively constant, but different from equilibrium concentrations. A continuous flux of mass and energy results in the constant synthesis and breakdown of molecules via chemical reactions of biochemical pathways. Essentially, steady state can be thought of as homeostasis at a cellular level.

Substrate-level phosphorylation is a metabolism reaction that results in the production of ATP or GTP supported by the energy released from another high-energy bond that leads to phosphorylation of ADP or GDP to ATP or GTP (note that the reaction catalyzed by creatine kinase is not considered as "substrate-level phosphorylation"). This process uses some of the released chemical energy, the Gibbs free energy, to transfer a phosphoryl (PO3) group to ADP or GDP. Occurs in glycolysis and in the citric acid cycle.

<span class="mw-page-title-main">Phosphoenolpyruvic acid</span> Chemical compound

Phosphoenolpyruvate is the carboxylic acid derived from the enol of pyruvate and phosphate. It exists as an anion. PEP is an important intermediate in biochemistry. It has the highest-energy phosphate bond found in organisms, and is involved in glycolysis and gluconeogenesis. In plants, it is also involved in the biosynthesis of various aromatic compounds, and in carbon fixation; in bacteria, it is also used as the source of energy for the phosphotransferase system.

<span class="mw-page-title-main">1,3-Bisphosphoglyceric acid</span> Chemical compound

1,3-Bisphosphoglyceric acid (1,3-Bisphosphoglycerate or 1,3BPG) is a 3-carbon organic molecule present in most, if not all, living organisms. It primarily exists as a metabolic intermediate in both glycolysis during respiration and the Calvin cycle during photosynthesis. 1,3BPG is a transitional stage between glycerate 3-phosphate and glyceraldehyde 3-phosphate during the fixation/reduction of CO2. 1,3BPG is also a precursor to 2,3-bisphosphoglycerate which in turn is a reaction intermediate in the glycolytic pathway.

<span class="mw-page-title-main">Fructose 6-phosphate</span> Chemical compound

Fructose 6-phosphate is a derivative of fructose, which has been phosphorylated at the 6-hydroxy group. It is one of several possible fructosephosphates. The β-D-form of this compound is very common in cells. The great majority of glucose is converted to fructose 6-phosphate upon entering a cell. Fructose is predominantly converted to fructose 1-phosphate by fructokinase following cellular import.

Flux, or metabolic flux is the rate of turnover of molecules through a metabolic pathway. Flux is regulated by the enzymes involved in a pathway. Within cells, regulation of flux is vital for all metabolic pathways to regulate the pathway's activity under different conditions. Flux is therefore of great interest in metabolic network modelling, where it is analysed via flux balance analysis and metabolic control analysis.

A futile cycle, also known as a substrate cycle, occurs when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than to dissipate energy in the form of heat. The reason this cycle was called "futile" cycle was because it appeared that this cycle operated with no net utility for the organism. As such, it was thought of being a quirk of the metabolism and thus named a futile cycle. After further investigation it was seen that futile cycles are very important for regulating the concentrations of metabolites. For example, if glycolysis and gluconeogenesis were to be active at the same time, glucose would be converted to pyruvate by glycolysis and then converted back to glucose by gluconeogenesis, with an overall consumption of ATP. Futile cycles may have a role in metabolic regulation, where a futile cycle would be a system oscillating between two states and very sensitive to small changes in the activity of any of the enzymes involved. The cycle does generate heat, and may be used to maintain thermal homeostasis, for example in the brown adipose tissue of young mammals, or to generate heat rapidly, for example in insect flight muscles and in hibernating animals during periodical arousal from torpor. It has been reported that the glucose metabolism substrate cycle is not a futile cycle but a regulatory process. For example, when energy is suddenly needed, ATP is replaced by AMP, a much more reactive adenine.

<span class="mw-page-title-main">Bioenergetic systems</span> Metabolic processes for energy production

Bioenergetic systems are metabolic processes that relate to the flow of energy in living organisms. Those processes convert energy into adenosine triphosphate (ATP), which is the form suitable for muscular activity. There are two main forms of synthesis of ATP: aerobic, which uses oxygen from the bloodstream, and anaerobic, which does not. Bioenergetics is the field of biology that studies bioenergetic systems.

References

  1. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 24.
  2. ↑ Green, D. E.; Zande, H. D. (1981). "Universal energy principle of biological systems and the unity of bioenergetics". Proceedings of the National Academy of Sciences of the United States of America. 78 (9): 5344–5347. Bibcode:1981PNAS...78.5344G. doi: 10.1073/pnas.78.9.5344 . PMC   348741 . PMID   6946475.
  3. 1 2 Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 27.
  4. 1 2 3 Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 24.
  5. 1 2 Ferrick, David A.; Neilson, Andy; Beeson, Craig (March 2008). "Advances in measuring cellular bioenergetics using extracellular flux". Drug Discovery Today. 13 (5–6): 268–274. doi:10.1016/j.drudis.2007.12.008. ISSN   1359-6446. PMID   18342804.
  6. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 506.
  7. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 28.
  8. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 22.
  9. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pgs. 22, 506.
  10. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 522- 523.
  11. ↑ Hardie, D. Grahame; Ross, Fiona A.; Hawley, Simon A. (April 2012). "AMPK: a nutrient and energy sensor that maintains energy homeostasis". Nature Reviews Molecular Cell Biology. 13 (4): 251–262. doi:10.1038/nrm3311. ISSN   1471-0080. PMC   5726489 . PMID   22436748.
  12. ↑ "CHAPTER 3: CALCULATION OF THE ENERGY CONTENT OF FOODS - ENERGY CONVERSION FACTORS". www.fao.org. Archived from the original on 2023-03-21. Retrieved 2023-05-08.
  13. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 502.
  14. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg. 503.
  15. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., p. 23.
  16. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 544.
  17. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 568.
  18. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 633.
  19. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 640.
  20. ↑ Masood W, Annamaraju P, Khan Suheb MZ, et al. Ketogenic Diet. [Updated 2023 Jun 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499830/ Archived 2021-06-14 at the Wayback Machine
  21. ↑ Devrim-Lanpir, Aslı, Lee Hill, and Beat Knechtle. 2021. "Efficacy of Popular Diets Applied by Endurance Athletes on Sports Performance: Beneficial or Detrimental? A Narrative Review" Nutrients 13, no. 2: 491. https://doi.org/10.3390/nu13020491
  22. 1 2 Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 731.
  23. ↑ Nelson, David L., Cox, Michael M. Lehninger: Principles of Biochemistry. New York: W.H. Freeman and Company, 2013. Sixth ed., pg 734.
  24. ↑ Robert K. Crane, D. Miller and I. Bihler. "The restrictions on possible mechanisms of intestinal transport of sugars". In: Membrane Transport and Metabolism. Proceedings of a Symposium held in Prague, August 22–27, 1960. Edited by A. Kleinzeller and A. Kotyk. Czech Academy of Sciences, Prague, 1961, pp. 439-449.
  25. ↑ Wright, Ernest M.; Turk, Eric (2004). "The sodium glucose cotransport family SLC5". Pflügers Arch. 447 (5): 510–8. doi:10.1007/s00424-003-1063-6. PMID   12748858. S2CID   41985805. Crane in 1961 was the first to formulate the cotransport concept to explain active transport [7]. Specifically, he proposed that the accumulation of glucose in the intestinal epithelium across the brush border membrane was coupled to downhill Na+
     transport cross the brush border. This hypothesis was rapidly tested, refined and extended [to] encompass the active transport of a diverse range of molecules and ions into virtually every cell type.
  26. ↑ Boyd, C A R (2008). "Facts, fantasies and fun in epithelial physiology". Experimental Physiology. 93 (3): 303–14. doi: 10.1113/expphysiol.2007.037523 . PMID   18192340. S2CID   41086034. the insight from this time that remains in all current text books is the notion of Robert Crane published originally as an appendix to a symposium paper published in 1960 (Crane et al. 1960). The key point here was 'flux coupling', the cotransport of sodium and glucose in the apical membrane of the small intestinal epithelial cell. Half a century later this idea has turned into one of the most studied of all transporter proteins (SGLT1), the sodium–glucose cotransporter.
  27. ↑ Peter Mitchell (1961). "Coupling of phosphorylation to electron and hydrogen transfer by a chemi-osmotic type of mechanism". Nature. 191 (4784): 144–8. Bibcode:1961Natur.191..144M. doi:10.1038/191144a0. PMID   13771349. S2CID   1784050.
  28. ↑ Boyer, Paul (1997). "THE ATP SYNTHASE—A SPLENDID MOLECULAR MACHINE". Annual Review of Biochemistry. 66: 717–749. doi:10.1146/annurev.biochem.66.1.717. PMID   9242922 . Retrieved 18 July 2024.
  29. ↑ Mitchell, Peter (11 March 1985). "Molecular mechanics of protonmotive F 0 F 1 ATPases: Rolling well and turnstile hypothesis". FEBS Letters. 182 (1): 1–7. Bibcode:1985FEBSL.182....1M. doi:10.1016/0014-5793(85)81142-X. ISSN   0014-5793. PMID   2857661.
  30. ↑ Orel, Valeri E. (October 1998). "Biological mechanochemiemission and bioenergetics". Bioelectrochemistry and Bioenergetics. 46 (2): 273–278. doi:10.1016/S0302-4598(98)00133-0.
  31. ↑ Malenka RC, Nestler EJ, Hyman SE (2009). Sydor A, Brown RY (ed.). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. pp. 179, 262–263. ISBN   9780071481274. Orexin neurons are regulated by peripheral mediators that carry information about energy balance, including glucose, leptin, and ghrelin. ... Accordingly, orexin plays a role in the regulation of energy homeostasis, reward, and perhaps more generally in emotion. ... The regulation of energy balance involves the exquisite coordination of food intake and energy expenditure. Experiments in the 1940s and 1950s showed that lesions of the lateral hypothalamus (LH) reduced food intake; hence, the normal role of this brain area is to stimulate feeding and decrease energy utilization. In contrast, lesions of the medial hypothalamus, especially the ventromedial nucleus (VMH) but also the PVN and dorsomedial hypothalamic nucleus (DMH), increased food intake; hence, the normal role of these regions is to suppress feeding and increase energy utilization. Yet discovery of the complex networks of neuropeptides and other neurotransmitters acting within the hypothalamus and other brain regions to regulate food intake and energy expenditure began in earnest in 1994 with the cloning of the leptin (ob, for obesity) gene. Indeed, there is now explosive interest in basic feeding mechanisms given the epidemic proportions of obesity in our society, and the increased toll of the eating disorders, anorexia nervosa and bulimia. Unfortunately, despite dramatic advances in the basic neurobiology of feeding, our understanding of the etiology of these conditions and our ability to intervene clinically remain limited.
  32. ↑ Morton GJ, Meek TH, Schwartz MW (2014). "Neurobiology of food intake in health and disease". Nat. Rev. Neurosci. 15 (6): 367–378. doi:10.1038/nrn3745. PMC   4076116 . PMID   24840801. However, in normal individuals, body weight and body fat content are typically quite stable over time2,3 owing to a biological process termed 'energy homeostasis' that matches energy intake to expenditure over long periods of time. The energy homeostasis system comprises neurons in the mediobasal hypothalamus and other brain areas4 that are a part of a neurocircuit that regulates food intake in response to input from humoral signals that circulate at concentrations proportionate to body fat content4-6. ... An emerging concept in the neurobiology of food intake is that neurocircuits exist that are normally inhibited, but when activated in response to emergent or stressful stimuli they can override the homeostatic control of energy balance. Understanding how these circuits interact with the energy homeostasis system is fundamental to understanding the control of food intake and may bear on the pathogenesis of disorders at both ends of the body weight spectrum.

Further reading

  1. ↑ Juretić, Davor (2022). Bioenergetics : a bridge across life and universe. Boca Raton, FL: CRC Press. ISBN   978-0-8153-8838-8. OCLC   1237252428.
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