Residue (chemistry)

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Distillation apparatus Distillation 2-a.jpg
Distillation apparatus

In chemistry, residue is whatever remains or acts as a contaminant after a given class of events. Residue may be the material remaining after a process of preparation, separation, or purification, such as distillation, evaporation, or filtration. It may also denote the undesired by-products of a chemical reaction.

Contents

Residues as an undesired by-product are a concern in agricultural and food industries.

Food safety

Toxic chemical residues, wastes or contamination from other processes, are a concern in food safety. The most common food residues originate from pesticides, veterinary drugs, and industrial chemicals. [1] For example, the U.S. Food and Drug Administration (FDA) and the Canadian Food Inspection Agency (CFIA) have guidelines for detecting chemical residues that are possibly dangerous to consume. [2] [3] In the U.S., the FDA is responsible for setting guidelines while other organizations enforce them.

Environmental concerns

Similar to the food industry, in environmental sciences residue also refers to chemical contaminants. Residues in the environment are often the result of industrial processes, such as escaped chemicals from mining processing, fuel leaks during industrial transportation, trace amounts of radioactive material, and excess pesticides that enter the soil. [4]

3D image of Aflatoxin Aflatoxin 3d.png
3D image of Aflatoxin

Characteristic units within a molecule

Residue may refer to an atom or a group of atoms that form part of a molecule, such as a methyl group.

Biochemistry

In biochemistry and molecular biology, the term residue refers to a specific monomer within the polymeric chain of a polysaccharide, protein or nucleic acid.

In proteins, the carboxyl group of one amino acid links with the amino group of another amino acid to form a peptide. This results in the removal of water, and what remains is called the residue. In naming residues, the word acid is replaced with residue. [5] A residue's properties will influence interactions with other residues and the overall chemical properties of the protein it resides in. One might say, "This protein consists of 118 amino acid residues" or "The histidine residue is considered to be basic because it contains an imidazole ring." Note that a residue is different from a moiety, which, in the above example would be constituted by the imidazole ring or the imidazole moiety.

A DNA or RNA residue is a single nucleotide in a nucleic acid. Examples of residues in DNA are the bases "A", "T", "G", and "C".

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<span class="mw-page-title-main">Amino acid</span> Organic compounds containing amine and carboxylic groups

Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 appear in the genetic code of life.

<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 that 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">Biopolymer</span> Polymer produced by a living organism

Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, classified according to the monomers used and the structure of the biopolymer formed: polynucleotides, polypeptides, and polysaccharides. The Polynucleotides, RNA and DNA, are long polymers of nucleotides. Polypeptides include proteins and shorter polymers of amino acids; some major examples include collagen, actin, and fibrin. Polysaccharides are linear or branched chains of sugar carbohydrates; examples include starch, cellulose, and alginate. Other examples of biopolymers include natural rubbers, suberin and lignin, cutin and cutan, melanin, and polyhydroxyalkanoates (PHAs).

<span class="mw-page-title-main">Chymotrypsin</span> Digestive enzyme

Chymotrypsin (EC 3.4.21.1, chymotrypsins A and B, alpha-chymar ophth, avazyme, chymar, chymotest, enzeon, quimar, quimotrase, alpha-chymar, alpha-chymotrypsin A, alpha-chymotrypsin) is a digestive enzyme component of pancreatic juice acting in the duodenum, where it performs proteolysis, the breakdown of proteins and polypeptides. Chymotrypsin preferentially cleaves peptide amide bonds where the side chain of the amino acid N-terminal to the scissile amide bond (the P1 position) is a large hydrophobic amino acid (tyrosine, tryptophan, and phenylalanine). These amino acids contain an aromatic ring in their side chain that fits into a hydrophobic pocket (the S1 position) of the enzyme. It is activated in the presence of trypsin. The hydrophobic and shape complementarity between the peptide substrate P1 side chain and the enzyme S1 binding cavity accounts for the substrate specificity of this enzyme. Chymotrypsin also hydrolyzes other amide bonds in peptides at slower rates, particularly those containing leucine at the P1 position.

<span class="mw-page-title-main">Denaturation (biochemistry)</span> Loss of structure in proteins and nucleic acids due to external stress

In biochemistry, denaturation is a process in which proteins or nucleic acids lose folded structure present in their native state due to various factors, including application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent, agitation and radiation, or heat. If proteins in a living cell are denatured, this results in disruption of cell activity and possibly cell death. Protein denaturation is also a consequence of cell death. Denatured proteins can exhibit a wide range of characteristics, from conformational change and loss of solubility or dissociation of cofactors to aggregation due to the exposure of hydrophobic groups. The loss of solubility as a result of denaturation is called coagulation. Denatured proteins lose their 3D structure, and therefore, cannot function.

<span class="mw-page-title-main">Protein</span> Biomolecule consisting of chains of amino acid residues

Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity.

<span class="mw-page-title-main">Protein primary structure</span> Linear sequence of amino acids in a peptide or protein

Protein primary structure is the linear sequence of amino acids in a peptide or protein. By convention, the primary structure of a protein is reported starting from the amino-terminal (N) end to the carboxyl-terminal (C) end. Protein biosynthesis is most commonly performed by ribosomes in cells. Peptides can also be synthesized in the laboratory. Protein primary structures can be directly sequenced, or inferred from DNA sequences.

<span class="mw-page-title-main">Proteolysis</span> Breakdown of proteins into smaller polypeptides or amino acids

Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, but may also occur by intra-molecular digestion.

<span class="mw-page-title-main">Protease</span> Enzyme that cleaves other proteins into smaller peptides

A protease is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds. Proteases are involved in numerous biological pathways, including digestion of ingested proteins, protein catabolism, and cell signaling.

<span class="mw-page-title-main">Post-translational modification</span> Chemical changes in proteins following their translation from mRNA

In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translate mRNA into polypeptide chains, which may then change to form the mature protein product. PTMs are important components in cell signalling, as for example when prohormones are converted to hormones.

In polymer science, the polymer chain or simply backbone of a polymer is the main chain of a polymer. Polymers are often classified according to the elements in the main chains. The character of the backbone, i.e. its flexibility, determines the properties of the polymer. For example, in polysiloxanes (silicone), the backbone chain is very flexible, which results in a very low glass transition temperature of −123 °C. The polymers with rigid backbones are prone to crystallization in thin films and in solution. Crystallization in its turn affects the optical properties of the polymers, its optical band gap and electronic levels.

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<span class="mw-page-title-main">Codex Alimentarius</span> Collection of internationally recognized food standards

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<span class="mw-page-title-main">Fine chemical</span> Pure chemical substances produced by and for the chemical industry

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Dietary exposure assessments in the United States involve the evaluation of dietary consumption and chemical residue data while taking into consideration additional factors that may affect a specified population of interest or sensitive population. The process of conducting a dietary exposure assessment involves the determination of the chemical residues on a particular food or foods and the calculation of the dietary exposure to these chemicals based on consumption data for the specified food or foods. A dietary exposure assessment allows a comparison to a relevant health standard such as the acceptable daily intake (ADI), the acute reference dose.

References

  1. "Chemical Residues and Contaminants". Food Safety and Inspection Service U.S. Department of Agriculture. July 28, 2023.
  2. "Drug & Chemical Residues Methods". U.S. Food and Drug Administration.
  3. "Chemical Residues / Microbiology - Food". Canadian Food Inspection Agency.
  4. Tudi, Muyesaier; Daniel Ruan, Huada; Wang, Li; Lyu, Jia; Sadler, Ross; Connell, Des; Chu, Cordia; Phung, Dung Tri (February 2021). "Agriculture Development, Pesticide Application and Its Impact on the Environment". International Journal of Environmental Research and Public Health. 18 (3): 1112. doi: 10.3390/ijerph18031112 . ISSN   1661-7827. PMC   7908628 . PMID   33513796.
  5. "Nomenclature and symbolism for amino acids and peptides (Recommendations 1983)". Pure and Applied Chemistry. 56 (5): 595–624. 1984-01-01. doi:10.1351/pac198456050595. ISSN   1365-3075.