Anabolism

Anabolism (/əˈnæbəlɪsm/) is the set of metabolic pathways that construct molecules from smaller units.[1] These reactions require energy, known also as an endergonic process.[2] Anabolism is the building-up aspect of metabolism, whereas catabolism is the breaking-down aspect. Anabolism is usually synonymous with biosynthesis.

Pathway

Polymerization, an anabolic pathway used to build macromolecules such as nucleic acids, proteins, and polysaccharides, uses condensation reactions to join monomers.[3] Macromolecules are created from smaller molecules using enzymes and cofactors.

Catabolism, energy carriers and anabolism
Use of ATP to drive the endergonic process of anabolism.

Energy source

Anabolism is powered by catabolism, where large molecules are broken down into smaller parts and then used up in cellular respiration. Many anabolic processes are powered by the cleavage of adenosine triphosphate (ATP).[4] Anabolism usually involves reduction and decreases entropy, making it unfavorable without energy input.[5] The starting materials, called the precursor molecules, are joined together using the chemical energy made available from hydrolyzing ATP, reducing the cofactors NAD+, NADP+, and FAD, or performing other favorable side reactions.[6] Occasionally it can also be driven by entropy without energy input, in cases like the formation of the phospholipid bilayer of a cell, where hydrophobic interactions aggregate the molecules.[7]

Cofactors

The reducing agents NADH, NADPH, and FADH2,[8] as well as metal ions,[3] act as cofactors at various steps in anabolic pathways. NADH, NADPH, and FADH2 act as electron carriers, while charged metal ions within enzymes stabilize charged functional groups on substrates.

Substrates

Substrates for anabolism are mostly intermediates taken from catabolic pathways during periods of high energy charge in the cell.[9]

Functions

Anabolic processes build organs and tissues. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. Examples of anabolic processes include the growth and mineralization of bone and increases in muscle mass.

Anabolic hormones

Endocrinologists have traditionally classified hormones as anabolic or catabolic, depending on which part of metabolism they stimulate. The classic anabolic hormones are the anabolic steroids, which stimulate protein synthesis and muscle growth, and insulin.

Photosynthetic carbohydrate synthesis

Photosynthetic carbohydrate synthesis in plants and certain bacteria is an anabolic process that produces glucose, cellulose, starch, lipids, and proteins from CO2.[5] It uses the energy produced from the light-driven reactions of photosynthesis, and creates the precursors to these large molecules via carbon assimilation in the photosynthetic carbon reduction cycle, a.k.a. the Calvin cycle.[9]

Amino acid biosynthesis overview
Amino acid biosynthesis from intermediates of glycolysis and the citric acid cycle.

Amino acid biosynthesis

All amino acids are formed from intermediates in the catabolic processes of glycolysis, the citric acid cycle, or the pentose phosphate pathway. From glycolysis, glucose 6-phosphate is a precursor for histidine; 3-phosphoglycerate is a precursor for glycine and cysteine; phosphoenol pyruvate, combined with the 3-phosphoglycerate-derivative erythrose 4-phosphate, forms tryptophan, phenylalanine, and tyrosine; and pyruvate is a precursor for alanine, valine, leucine, and isoleucine. From the citric acid cycle, α-ketoglutarate is converted into glutamate and subsequently glutamine, proline, and arginine; and oxaloacetate is converted into aspartate and subsequently asparagine, methionine, threonine, and lysine.[9]

Glycogen storage

During periods of high blood sugar, glucose 6-phosphate from glycolysis is diverted to the glycogen-storing pathway. It is changed to glucose-1-phosphate by phosphoglucomutase and then to UDP-glucose by UTP--glucose-1-phosphate uridylyltransferase. Glycogen synthase adds this UDP-glucose to a glycogen chain.[9]

Gluconeogenesis

Glucagon is traditionally a catabolic hormone, but also stimulates the anabolic process of gluconeogenesis by the liver, and to a lesser extent the kidney cortex and intestines, during starvation to prevent low blood sugar.[8] It is the process of converting pyruvate into glucose. Pyruvate can come from the breakdown of glucose, lactate, amino acids, or glycerol.[10] The gluconeogenesis pathway has many reversible enzymatic processes in common with glycolysis, but it is not the process of glycolysis in reverse. It uses different irreversible enzymes to ensure the overall pathway runs in one direction only.[10]

Regulation

Anabolism operates with separate enzymes from catalysis, which undergo irreversible steps at some point in their pathways. This allows the cell to regulate the rate of production and prevent an infinite loop, also known as a futile cycle, from forming with catabolism.[9]

The balance between anabolism and catabolism is sensitive to ADP and ATP, otherwise known as the energy charge of the cell. High amounts of ATP cause cells to favor the anabolic pathway and slow catabolic activity, while excess ADP slows anabolism and favors catabolism.[9] These pathways are also regulated by circadian rhythms, with processes such as glycolysis fluctuating to match an animal's normal periods of activity throughout the day.[11]

Etymology

The word anabolism is from New Latin, which got the roots from Greek: ἁνά, "upward" and βάλλειν, "to throw".

References

  1. ^ de Bolster MW (1997). "Glossary of Terms Used in Bioinorganic Chemistry: Anabolism". International Union of Pure and Applied Chemistry. Archived from the original on 30 October 2007. Retrieved 2007-10-30.
  2. ^ Rye C, Wise R, Jurukovski V, Choi J, Avissar Y (2013). Biology. Rice University, Houston Texas: OpenStax. ISBN 978-1-938168-09-3.
  3. ^ a b Alberts B, Johnson A, Julian L, Raff M, Roberts K, Walter P (2002). Molecular Biology of the Cell (5th ed.). CRC Press. ISBN 978-0-8153-3218-3. Archived from the original on 6 June 2017. Retrieved 2018-11-01.
  4. ^ Nicholls DG, Ferguson SJ (2002). Bioenergetics (3rd ed.). Academic Press. ISBN 978-0-12-518121-1.
  5. ^ a b Ahern K, Rajagopal I (2013). Biochemistry Free and Easy (PDF) (2nd ed.). Oregon State University.
  6. ^ Voet D, Voet JG, Pratt CW (2013). Fundamentals of biochemistry : life at the molecular level (Fourth ed.). Hoboken, NJ: Wiley. ISBN 978-0-470-54784-7. OCLC 738349533.
  7. ^ Hanin I, Pepeu G. Phospholipids: biochemical, pharmaceutical, and analytical considerations. New York. ISBN 978-1-4757-1364-0. OCLC 885405600.
  8. ^ a b Jakubowski H (2002). "An Overview of Metabolic Pathways - Anabolism". Biochemistry Online. College of St. Benedict, St. John's University: LibreTexts.
  9. ^ a b c d e f Nelson DL, Lehninger AL, Cox MM (2013). Principles of Biochemistry. New York: W.H. Freeman. ISBN 978-1-4292-3414-6.
  10. ^ a b Berg JM, Tymoczko JL, Stryer L (2002). Biochemistry (5th ed.). New York: W.H. Freeman. ISBN 978-0-7167-3051-4. OCLC 48055706.
  11. ^ Ramsey KM, Marcheva B, Kohsaka A, Bass J (2007). "The clockwork of metabolism". Annual Review of Nutrition. 27: 219–40. doi:10.1146/annurev.nutr.27.061406.093546. PMID 17430084.
10-Formyltetrahydrofolate

10-Formyltetrahydrofolate (10-CHO-THF) is a form of tetrahydrofolate that acts as a donor of formyl groups in anabolism. In these reactions 10-CHO-THF is used as a substrate in formyltransferase reactions.

5-Methyl-7-methoxyisoflavone

5-Methyl-7-methoxyisoflavone, commonly referred to simply as methoxyisoflavone, is a chemical compound marketed as a bodybuilding supplement. However, there is no meaningful clinical evidence to support its usefulness. A study published in 2006 examined the effect of methoxyflavone on training adaptations and markers of muscle anabolism and catabolism. No measurable effects were observed in athletic performance or in levels of testosterone and cortisol.Consumption of 5-methyl-7-methoxyisoflavone can produce false positive results in urinary tests for cannabinoid use.

Amphibolic

The term amphibolic ( Ancient Greek: ἀμφί, translit. amphi, lit. 'both sides') is used to describe a biochemical pathway that involves both catabolism and and anabolism. Catabolism is a degradative phase of metabolism in which large molecule are converted into smaller and simpler molecule, which involves two types of reactions. First, hydrolysis reactions, in which catabolism is the breaking apart of molecules to smaller molecules to release energy. An example of a catabolic reaction is digestion and cellular respiration, where you break apart sugars and fats for energy. Hydrolysis is how this is done and it is approximately the reverse of a dehydration reaction. Breaking down a protein into amino acids or a triglyceride into fatty acids or a disaccharide into monosaccharides are all hydrolysis or catabolic reactions. Second, oxidation reactions involve the removal of hydrogens and electrons from an organic molecule. Anabolism is the biosynthesis phase of metabolism in which smaller simple precursor are converted to large and complex molecule of the cell. Anabolism has two classes of reactions, which are dehydration synthesis reaction, this type involves the joining of smaller molecules together to form larger, more complex molecules. This occurs through dehydration synthesis reactions. These are the most common ways smaller organic molecules can be formed into more complex ones and applies to the formation of carbs, proteins, lipids and nucleic acids. Other type called reduction reaction, which involves the adding of hydrogens and electrons to a molecule. Whenever you do that, it gains calories of energy because when you split a hydrocarbon bond, it releases energy).This term was proposed by B.Davis in 1961 to emphasise the dual metabolic role of such pathway. These pathway consider to be central metabolic pathways which provide, from catabolic sequences, the intermediates which form the substrate of the metabolic processes.

Biological process

Biological processes are the processes vital for a living organism to live, and that shape its capacities for interacting with its environment. Biological processes are made up of many chemical reactions or other events that are involved in the persistence and transformation of life forms. Metabolism and homeostasis are examples.

Regulation of biological processes occurs when any process is modulated in its frequency, rate or extent. Biological processes are regulated by many means; examples include the control of gene expression, protein modification or interaction with a protein or substrate molecule.

Homeostasis: regulation of the internal environment to maintain a constant state; for example, sweating to reduce temperature

Organization: being structurally composed of one or more cells – the basic units of life

Metabolism: transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.

Growth: maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.

Adaptation: the ability to change over time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity, diet, and external factors.

Response to stimuli: a response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.

Reproduction: the ability to produce new individual organisms, either asexually from a single parent organism or sexually from two parent organisms.

Interaction between organisms. the processes by which an organism has an observable effect on another organism of the same or different species.

Also: cellular differentiation, fermentation, fertilisation, germination, tropism, hybridisation, metamorphosis, morphogenesis, photosynthesis, transpiration.

Catabolism

Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, nucleic acids and proteins) into smaller units (such as monosaccharides, fatty acids, nucleotides, and amino acids, respectively). Catabolism is the breaking-down aspect of metabolism, whereas anabolism is the building-up aspect.

Cells use the monomers released from breaking down polymers to either construct new polymer molecules, or degrade the monomers further to simple waste products, releasing energy. Cellular wastes include lactic acid, acetic acid, carbon dioxide, ammonia, and urea. The creation of these wastes is usually an oxidation process involving a release of chemical free energy, some of which is lost as heat, but the rest of which is used to drive the synthesis of adenosine triphosphate (ATP). This molecule acts as a way for the cell to transfer the energy released by catabolism to the energy-requiring reactions that make up anabolism. (Catabolism is seen as destructive metabolism and anabolism as constructive metabolism). Catabolism therefore provides the chemical energy necessary for the maintenance and growth of cells. Examples of catabolic processes include glycolysis, the citric acid cycle, the breakdown of muscle protein in order to use amino acids as substrates for gluconeogenesis, the breakdown of fat in adipose tissue to fatty acids, and oxidative deamination of neurotransmitters by monoamine oxidase.

Condensation reaction

A condensation reaction is a class of organic addition reaction that typically proceeds in a step-wise fashion to produce the addition product, usually in equilibrium, and a water molecule (hence named condensation). The reaction may otherwise involve the functional groups of the molecule, and formation of a small molecule such as ammonia, ethanol, or acetic acid instead of water. It is a versatile class of reactions that can occur in acidic or basic conditions or in the presence of a catalyst. This class of reactions is a vital part of life as it is essential to the formation of peptide bonds between amino acids and the biosynthesis of fatty acids.

Many variations of condensation reactions exist, common examples include the aldol condensation, Claisen condensation, Knoevenagel condensation, and the Dieckman condensation (intramolecular Claisen condensation).

Fatty acid metabolism

Fatty acid metabolism consists of catabolic processes that generate energy, and anabolic processes that create biologically important molecules (triglycerides, phospholipids, second messengers, local hormones and ketone bodies).Fatty acids are a family of molecules classified within the lipid macronutrient class. One role of fatty acids in animal metabolism is energy production, captured in the form of adenosine triphosphate (ATP). When compared to other macronutrient classes (carbohydrates and protein), fatty acids yield the most ATP on an energy per gram basis, when they are completely oxidized to CO2 and water by beta oxidation and the citric acid cycle. Fatty acids (mainly in the form of triglycerides) are therefore the foremost storage form of fuel in most animals, and to a lesser extent in plants. In addition, fatty acids are important components of the phospholipids that form the phospholipid bilayers out of which all the membranes of the cell are constructed (the cell wall, and the membranes that enclose all the organelles within the cells, such as the nucleus, the mitochondria, endoplasmic reticulum, and the Golgi apparatus). Fatty acids can also be cleaved, or partially cleaved, from their chemical attachments in the cell membrane to form second messengers within the cell, and local hormones in the immediate vicinity of the cell. The prostaglandins made from arachidonic acid stored in the cell membrane, are probably the most well known group of these local hormones.

Green sulfur bacteria

The green sulfur bacteria (Chlorobiaceae) are a family of obligately anaerobic photoautotrophic bacteria. Together with the non-photosynthetic Ignavibacteriaceae, they form the phylum Chlorobi.Green sulfur bacteria are nonmotile (except Chloroherpeton thalassium, which may glide) and capable of anoxygenic photosynthesis. In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors. They are autotrophs that utilize the reverse tricarboxylic acid cycle to fix carbon dioxide. Green sulfur bacteria have been found in depths of up to 145m in the Black Sea, with low light availability.

Hyperaminoacidemia

Hyperaminoacidemia refers to the condition of having an excess of amino acids in the bloodstream. There is evidence that hyperaminoacidemia increases protein synthesis and anabolism.

List of natural phenomena

Types of natural phenomena include:

Weather, fog, thunder, tornadoes; biological processes, decomposition, germination; physical processes, wave propagation, erosion; tidal flow, and natural disasters such as electromagnetic pulses, volcanic eruptions, and earthquakes.

MK-0773

MK-0773, also known as PF-05314882, is a steroidal, orally active selective androgen receptor modulator (SARM) that was under development by Merck and GTx for the treatment of sarcopenia (loss of muscle mass) in women and men. Clinical trials for sarcopenia began in late 2007 but the collaboration between Merck and GTx ended in early 2010 and GTx terminated development of MK-0773 shortly thereafter.MK-0773 is a 4-azasteroid and a potent and selective agonist of the androgen receptor (AR). It binds to the AR with an IC50 of 6.6 nM and is a partial agonist in transactivation modulation of the AR with an IP of 25 nM and Emax of 78% and has a TRAF2 Emax of 29% and a virilization (N/C interaction) counterscreen assay Emax of 2%. That is, it produces promoter activation but induces the N/C interaction almost negligibly. MK-0773 is reportedly four times as potent as testosterone as an agonist of the AR. The drug is selective and does not bind to other steroid hormone receptors such as the progesterone receptor or glucocorticoid receptor and shows no significant inhibition of 5α-reductase (IC50 > 10 μM). In addition, it is non-aromatizable and hence has no potential for estrogenic effects or side effects, like gynecomastia. MK-0773 had similar effects on lipid metabolism relative to DHT, including a decrease in total cholesterol and high-density lipoprotein (HDL) of a similar magnitude.MK-0773 shows tissue-selective androgenic effects in vivo in animals. It increases lean body mass with maximal anabolic effects that are approximately 80% of those of dihydrotestosterone (DHT). However, it had less than 5% of the effect of DHT on uterine weight, about 30 to 50% of the increase of sebaceous gland area induced by DHT, and increased the weight of the seminal vesicles by 12% of that of DHT at the highest dosage assessed. It had similarly reduced effects on the prostate gland. No significant increase in gene expression of six candidate genes of virilization was observed. As such, MK-0773 shows a profile of an anabolic SARM with limited effects on sebaceous glands and reproductive tissues in animals and a minimal propensity for virilization.In human clinical studies, MK-0773 produced anabolism in women and men while producing no or very low effects on sebaceous glands, the endometrium, or the prostate gland after 12 weeks of treatment. A decrease in total cholesterol and HDL was also observed in the clinical studies. MK-0773 produced a significant increase in lean body mass in elderly (≥65 years of age) women with sarcopenia and moderate physical dysfunction. It also increased muscle strength relative to placebo but this failed to reach statistical significance. MK-0773 has been associated with elevated liver enzymes in clinical studies.

Metabolic pathway

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. These enzymes often require dietary minerals, vitamins, and other cofactors to function.

Different metabolic pathways function based on the position within a eukaryotic cell and the significance of the pathway in the given compartment of the cell. For instance, the, electron transport chain, and oxidative phosphorylation all take place in the mitochondrial membrane. In contrast, glycolysis, pentose phosphate pathway, and fatty acid biosynthesis all occur in the cytosol of a cell.There are two types of metabolic pathways that are characterized by their ability to either synthesize molecules with the utilization of energy (anabolic pathway) or break down of complex molecules by releasing energy in the process (catabolic pathway). The two pathways complement each other in that the energy released from one is used up by the other. The degradative process of a catabolic pathway provides the energy required to conduct a biosynthesis of an anabolic pathway. In addition to the two distinct metabolic pathways is the amphibolic pathway, which can be either catabolic or anabolic based on the need for or the availability of energy.Pathways are required for the maintenance of homeostasis within an organism and the flux of metabolites through a pathway is regulated depending on the needs of the cell and the availability of the substrate. The end product of a pathway may be used immediately, initiate another metabolic pathway or be stored for later use. The metabolism of a cell consists of an elaborate network of interconnected pathways that enable the synthesis and breakdown of molecules (anabolism and catabolism).

Metabolism

Metabolism (, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous 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 transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism).

Metabolic reactions may be categorized as catabolic - the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic - the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.

The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts - they allow a reaction to proceed more rapidly - and they also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells.

The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The basal metabolic rate of an organism is the measure of the amount of energy consumed by all of these chemical reactions.

A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants. These similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and their retention because of their efficacy.

Methylotroph

Methylotrophs are a diverse group of microorganisms that can use reduced one-carbon compounds, such as methanol or methane, as the carbon source for their growth; and multi-carbon compounds that contain no carbon-carbon bonds, such as dimethyl ether and dimethylamine. This group of microorganisms also includes those capable of assimilating reduced one-carbon compounds by way of carbon dioxide using the ribulose bisphosphate pathway. These organisms should not be confused with methanogens which on the contrary produce methane as a by-product from various one-carbon compounds such as carbon dioxide.

Some methylotrophs can degrade the greenhouse gas methane, and in this case they are called methanotrophs. The methanotroph Methylococcus capsulatus is used to degrade methane and other substrates. The abundance, purity, and low price of methanol compared to commonly used sugars make methylotrophs competent organisms for production of amino acids, vitamins, recombinant proteins, single-cell proteins, co-enzymes and cytochromes.

Precursor (chemistry)

In chemistry, a precursor is a compound that participates in a chemical reaction that produces another compound.

In biochemistry, the term "precursor" often refers more specifically to a chemical compound preceding another in a metabolic pathway, such as a protein precursor.

Protein metabolism

Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism.

The steps of protein synthesis include transcription, translation, and post translational modifications. During transcription, RNA polymerase transcribes a coding region of the DNA in a cell producing a sequence of RNA, specifically messenger RNA (mRNA). This mRNA sequence contains codons: 3 nucleotide long segments that code for a specific amino acid. Ribosomes translate the codons to their respective amino acids. In humans, non-essential amino acids are synthesized from intermediates in major metabolic pathways such as the Citric Acid Cycle. Essential amino acids must be consumed and are made in other organisms. The amino acids are joined by peptide bonds making a polypeptide chain. This polypeptide chain then goes through post translational modifications and is sometimes joined with other polypeptide chains to form a fully functional protein.

Dietary proteins are first broken down to individual amino acids by various enzymes and hydrochloric acid present in the gastrointestinal tract. These amino acids are further broken down to α-keto acids which can be recycled in the body for generation of energy, and production of glucose or fat or other amino acids. Proteins can be broken down by enzymes known as peptidases or can break down as a result of denaturation. Proteins can denature in environmental conditions the protein is not made for.

Protein turnover

Protein turnover is the balance between protein synthesis and protein degradation. More synthesis than breakdown indicates an anabolic state that builds lean tissues, more breakdown than synthesis indicates a catabolic state that burns lean tissues. According to D.S. Dunlop, protein turnover occurs in brain cells the same as any other eukaryotic cells, but that "knowledge of those aspects of control and regulation specific or peculiar to brain is an essential element for understanding brain function."Protein turnover is believed to decrease with age in all senescent organisms including humans. This results in an increase in the amount of damaged protein within the body.

Four weeks of aerobic exercise has been shown to increase skeletal muscle protein turnover in previously unfit individuals. A diet high in protein increases whole body turnover in endurance athletes.Some bodybuilding supplements claim to reduce the protein breakdown by reducing or blocking the number of catabolic hormones within the body. This is believed to increase anabolism. However, if protein breakdown falls too low then the body would not be able to remove muscle cells that have been damaged during workouts which would in turn prevent the growth of new muscle cells.

When older proteins are broken down in the body, they must be replaced. This concept is called protein turnover, and different types of proteins have very different turnover rates. Protein synthesis occurs during the process of translation on ribosomes. Protein breakdown occurs generally in two cellular locations:

Lysosomal proteases digest endocytosed proteins

Cytoplasmic complexes, called proteasomes, digest older or abnormal proteins that have been tagged with ubiquitin for destruction.

Purple bacteria

Purple bacteria or purple photosynthetic bacteria are proteobacteria that are phototrophic, that is, capable of producing their own food via photosynthesis. They are pigmented with bacteriochlorophyll a or b, together with various carotenoids, which give them colours ranging between purple, red, brown, and orange. They may be divided into two groups – purple sulfur bacteria (Chromatiales, in part) and purple non-sulfur bacteria (Rhodospirillaceae). In a 2018 Frontiers in Energy Research paper, it has been suggested purple bacteria be used as a biorefinery.

Sleep and metabolism

Sleep is important in regulating metabolism. Mammalian sleep can be sub-divided into two distinct phases - REM (rapid eye movement) and non-REM (NREM) sleep. In humans and cats, NREM sleep has four stages, where the third and fourth stages are considered slow-wave sleep (SWS). SWS is considered deep sleep, when metabolism is least active.Metabolism involves two biochemical processes that occur in living organisms. The first is anabolism, which refers to the build up of molecules. The second is catabolism, the breakdown of molecules. These two processes work to regulate the amount of energy the body uses to maintain itself. During non-REM sleep, metabolic rate and brain temperature are lowered to deal with damages that may have occurred during time of wakefulness.

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