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Catabolism

 

 
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Catabolism
 
 
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Catabolism is the set of metabolic pathway
Metabolic pathway

In biochemistry, a metabolic pathway is a series of chemistry reactions occurring within a cell . In each pathway, a principal chemical is modified by chemical reactions....
s which break down molecules into smaller units and release energy
Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
. In catabolism, large molecules such as polysaccharide
Polysaccharide

Polysaccharides are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined together by glycosidic bonds. They are therefore very large, often branched, macromolecules....
s, lipid
Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
s, nucleic acid
Nucleic acid

A nucleic acid is a macromolecule composed of chains of monomeric nucleotides. In biochemistry these molecules carry genetic information or form structures within Cell ....
s and protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s are broken down into smaller units such as monosaccharide
Monosaccharide

Monosaccharides are the most basic unit of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystal solids....
s, fatty acid
Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail , which is either saturation or Unsaturated compound....
s, nucleotide
Nucleotide

Nucleotides are molecules that comprise the structural units of RNA and DNA. Additionally, nucleotides play central roles in metabolism. In that capacity, they serve as sources of chemical energy , participate in cell signaling , and are incorporated into important cofactors of enzymatic reactions ....
s and amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
s, respectively. As molecules such as polysaccharides, proteins and nucleic acids are made from long chains of these small monomer
Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
 units, the large molecules are called polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s.

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.






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Catabolism is the set of metabolic pathway
Metabolic pathway

In biochemistry, a metabolic pathway is a series of chemistry reactions occurring within a cell . In each pathway, a principal chemical is modified by chemical reactions....
s which break down molecules into smaller units and release energy
Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
. In catabolism, large molecules such as polysaccharide
Polysaccharide

Polysaccharides are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined together by glycosidic bonds. They are therefore very large, often branched, macromolecules....
s, lipid
Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
s, nucleic acid
Nucleic acid

A nucleic acid is a macromolecule composed of chains of monomeric nucleotides. In biochemistry these molecules carry genetic information or form structures within Cell ....
s and protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s are broken down into smaller units such as monosaccharide
Monosaccharide

Monosaccharides are the most basic unit of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystal solids....
s, fatty acid
Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail , which is either saturation or Unsaturated compound....
s, nucleotide
Nucleotide

Nucleotides are molecules that comprise the structural units of RNA and DNA. Additionally, nucleotides play central roles in metabolism. In that capacity, they serve as sources of chemical energy , participate in cell signaling , and are incorporated into important cofactors of enzymatic reactions ....
s and amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
s, respectively. As molecules such as polysaccharides, proteins and nucleic acids are made from long chains of these small monomer
Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
 units, the large molecules are called polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s.

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
Lactic acid

Lactic acid , also known as milk acid, is a chemical compound that plays a role in several biochemistry processes. It was first isolated in 1780 by a Swedish chemist, Carl Wilhelm Scheele, and is a carboxylic acid with a chemical formula of C3H6O3....
, acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
, carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
, ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
, and urea
Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
. The creation of these wastes is usually an oxidation process involving a release of chemical free energy, some of which is lost as heat
Heat

In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature....
, but the rest is used to drive the synthesis of adenosine triphosphate
Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
 (ATP). This molecule acts as a way for the cell to transfer the energy released by catabolism to the energy-requiring reactions which make up anabolism
Anabolism

Anabolism is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy. One way of categorizing metabolic processes, whether at the cell ular, organ or organism level is as 'anabolic' or as 'catabolism', which is the opposite....
. Catabolism therefore provides the chemical energy necessary for the maintenance and growth of cells. Examples of catabolic processes include glycolysis
Glycolysis

Glycolysis is the metabolic pathway that converts glucose, C6H12O6, into pyruvate, C3H5O3-....
, the citric acid cycle
Citric acid cycle

The citric acid cycle ? also known as the tricarboxylic acid cycle ; the Krebs cycle; or, more rarely, the Szent-Gy?rgyi-Krebs cycle) ? is a series of enzyme-catalysed chemical reactions of central importance in all living cell s that use oxygen as part of cellular respiration....
, the breakdown of muscle protein in order to use amino acids as substrate
Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalysis chemical reactions involving the substrate. The substrate binds with the enzyme active site, and an enzyme-substrate complex is formed....
s for gluconeogenesis
Gluconeogenesis

Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactic acid, glycerol, and glucogenic amino acids....
 and breakdown of fat
Fat

Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. Chemistry, fats are generally ester of glycerol and fatty acids....
 in adipose tissue
Adipose tissue

In histology, adipose tissue or fat is loose connective tissue composed of adipocytes. Adipose tissue is derived from lipoblasts. Its main role is to store energy in the form of fat, although it also cushions and Thermal insulation the body....
 to fatty acid
Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail , which is either saturation or Unsaturated compound....
s.

There are many signals which control catabolism. Most of the known signals are hormone
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
s and the molecules involved in metabolism itself. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic, depending on which part of metabolism they stimulate. The "classic" catabolic hormones known since the early 20th century are cortisol
Cortisol

Cortisol is a corticosteroid hormone or glucocorticoid produced by the adrenal cortex, that is part of the adrenal gland . It is usually referred to as the "stress hormone" as it is involved in response to stress and anxiety, controlled by Corticotropin-releasing hormone....
, glucagon
Glucagon

Glucagon is an important hormone involved in carbohydrate metabolism. Produced by the pancreas, it is released when the glucose level in the blood is low , causing the liver to convert stored glycogen into glucose and release it into the bloodstream....
, and adrenaline (and other catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s). In recent decades, many more hormones with at least some catabolic effects have been discovered, including cytokine
Cytokine

Cytokines are a category of signaling molecules that, like hormones and neurotransmitters, are used extensively in cell communication. They are proteins, peptides or glycoproteins....
s, orexin
Orexin

Orexins, also called hypocretins, are the common names given to a pair of highly excitatory neuropeptide hormones that were simultaneously discovered by two groups of researchers in rat brains....
 and hypocretin (a hormone pair), and melatonin
Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae....
.

See also

  • Anabolism
    Anabolism

    Anabolism is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy. One way of categorizing metabolic processes, whether at the cell ular, organ or organism level is as 'anabolic' or as 'catabolism', which is the opposite....
  • Autophagy
    Autophagy

    In cell biology, autophagy, or autophagocytosis, is a catabolic process involving the degradation of a cell's own components through the lysosome machinery....
  • Dehydration synthesis
  • Hydrolysis
    Hydrolysis

    Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
  • Metabolism
    Metabolism

    Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....