Download Biochemistry and biomedical uses

INTRODUCTION TO BIOSTATICS
ANSWERS
1. An antibacterial is an agent that inhibits bacterial growth or kills bacteria.1 The term is often
used synonymously with the term antibiotic(s). Today, however, with increased knowledge of the
causative agents of various infectious diseases, antibiotic(s) has come to denote a broader range
of antimicrobial compounds, including anti-fungal and other compounds.2 Antibacterials must be
distinguished from disinfectants (sanitizing agents), which are less-selective substances used to
destroy microorganisms.
The term antibiotic was first used in 1942 by Selman Waksman and his collaborators in journal articles to
describe any substance produced by a microorganism that is antagonistic to the growth of other
microorganisms in high dilution.3 This definition excluded substances that kill bacteria but are not
produced by microorganisms (such as gastric juices and hydrogen peroxide). It also
excluded synthetic antibacterial compounds such as the sulfonamides. Many antibacterial compounds are
relatively small molecules with a molecular weight of less than 2000 atomic mass units.
With advances in medicinal chemistry, most of today's antibacterials are semisynthetic modifications of
various natural compounds.4 These include, for example, the beta-lactam antibacterials, which include
the penicillins (produced by fungi in the genus Penicillium), the cephalosporins, and the carbapenems.
Compounds that are still isolated from living organisms are theaminoglycosides, whereas other
antibacterials—for example, the sulfonamides, the quinolones, and the oxazolidinones—are produced
solely by chemical synthesis. In accordance with this, many antibacterial compounds are classified on the
basis of chemical/biosynthetic origin into natural, semisynthetic, and synthetic. Another classification
system is based on biological activity; in this classification, antibacterials are divided into two broad
groups according to their biological effect on microorganisms: Bactericidal agents kill bacteria,
and bacteriostatic agents slow down or stall bacterial growth.
2.Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as
foods, pharmaceuticals, paints, biological samples, wood, etc. to preventdecomposition by microbial growth or
by undesirable chemical changes. Preservatives can be divided into two types, depending on their origin. Class
I preservatives refers to those preservatives which are naturally occurring, everyday substances. Examples
include salt, honey and wood smoke.1 Class II preservatives refer to preservatives which are synthetically
manufactured.1
Preservatives in wood
Preservatives may be added to wood to prevent the growth of fungi as well as to repel insects and termites.
Typically arsenic, copper, chromium, borate, and petroleum based chemical compounds are used. For more
information on wood preservatives, see timber treatment.
Preservatives in foods
Preservatives are often added to food to prevent their spoilage, or to retain their nutritional value and/or flavor
for a longer period. The basic approach is to eliminate microorganisms from the food and prevent their
regrowth. This is achieved by methods such as a high concentration of salt, or reducing the water content. This
inhibits spoilage of the food item by microbial growth.
Preservatives may be antimicrobial preservatives, which inhibit the growth of bacteria or fungi,
including mold or they can be antioxidants such as oxygen absorbers, which inhibit the oxidation of food
constituents. Common antimicrobial preservatives include sorbic acid and its salts, benzoic acid and its
salts, calcium propionate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite,potassium hydrogen sulfite,
etc.) and disodium EDTA.23 Antioxidants include BHA, BHT, TBHQ and propyl gallate.2 Other preservatives
include ethanol and methylchloroisothiazolinone. FDA standards do not currently require fruit and vegetable
product labels to reflect the type of chemical preservative(s) used on the produce.citation needed The benefits and
safety of many artificial food additives (including preservatives) are the subject of debate among academics
and regulators specializing in food science, toxicology, and biology.
Natural food preservation
Naturally occurring substances such as rosemary extract, hops, salt, sugar, vinegar, alcohol, diatomaceous
earth and castor oil are also used as traditional preservatives. Certain processes such
as freezing, pickling, smoking and salting can also be used to preserve food. Another group of preservatives
targets enzymes in fruits and vegetables that start to metabolize after they are cut. For instance, the naturally
occurring citric and ascorbic acids in lemon or other citrus juice can inhibit the action of the
enzyme phenolase which turns surfaces of cut apples and potatoes brown if a small amount of the juice is
applied to the freshly cut produce. Vitamin C and Vitamin E are also sometimes used as preservatives.
3.Disinfectant
Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on
the objects.1 Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is
less effective than sterilisation, which is an extreme physical and/or chemical process that kills all types of
life.1 Disinfectants are different from other antimicrobial agents such as antibiotics, which destroy
microorganisms within the body, and antiseptics, which destroy microorganisms on living tissue. Disinfectants
are also different from biocides — the latter are intended to destroy all forms of life, not just microorganisms.
Disinfectants work by destroying the cell wall of microbes or interfering with the metabolism.
Sanitisers are substances that simultaneously clean and disinfect. 2
Bacterial endospores are most resistant to disinfectants, but some viruses and bacteria also possess some
tolerance.
Disinfectants are frequently used in hospitals, dental surgeries, kitchens, and bathrooms to kill infectious
organisms.
Properties
A perfect disinfectant would also offer complete and full microbiological sterilisation, without harming humans
and useful forms of life, be inexpensive, and non-corrosive. However, most disinfectants are also, by nature,
potentially harmful (even toxic) to humans or animals. Most modern household disinfectants contain Bitrex, an
exceptionally bitter substance added to discourage ingestion, as a safety measure. Those that are used
indoors should never be mixed with other cleaning products as chemical reactions can occur.3 The choice of
disinfectant to be used depends on the particular situation. Some disinfectants have a wide spectrum (kill many
different types of microorganisms), while others kill a smaller range of disease-causing organisms but are
preferred for other properties (they may be non-corrosive, non-toxic, or inexpensive).4 There are arguments for
creating or maintaining conditions that are not conducive to bacterial survival and multiplication, rather than
attempting to kill them with chemicals. Bacteria can increase in number very quickly, which enables them
to evolve rapidly. Should some bacteria survive a chemical attack, they give rise to new generations composed
completely of bacteria that have resistance to the particular chemical used. Under a sustained chemical attack,
the surviving bacteria in successive generations are increasingly resistant to the chemical used, and ultimately
the chemical is rendered ineffective. For this reason, some question the wisdom of impregnating cloths,cutting
boards and worktops in the home with bactericidal chemicals.citation needed
Types
Air disinfectants
Air disinfectants are typically chemical substances capable of disinfecting microorganisms suspended in the air.
Disinfectants are generally assumed to be limited to use on surfaces, but that is not the case. In 1928, a study
found that airborne microorganisms could be killed using mists of dilute bleach. 5 An air disinfectant must be
dispersed either as an aerosol or vapour at a sufficient concentration in the air to cause the number of viable
infectious microorganisms to be significantly reduced.
In the 1940s and early 1950s, further studies showed inactivation of diverse bacteria, influenza virus,
and Penicillium chrysogenum (previously P. notatum) mold fungus using various glycols, principally propylene
glycol and triethylene glycol.6 In principle, these chemical substances are ideal air disinfectants because they
have both high lethality to microorganisms and low mammalian toxicity.78
Although glycols are effective air disinfectants in controlled laboratory environments, it is more difficult to use
them effectively in real-world environments because the disinfection of air is sensitive to continuous action.
Continuous action in real-world environments with outside air exchanges at door, HVAC, and window
interfaces, and in the presence of materials that adsorb and remove glycols from the air, poses engineering
challenges that are not critical for surface disinfection. The engineering challenge associated with creating a
sufficient concentration of the glycol vapours in the air have not to date been sufficiently addressed. 910
Alcohols
Alcohols, usually ethanol or isopropanol, are sometimes used as a disinfectant, but more often as
an antisepticcitation needed (the distinction being that alcohol tends to be used on living tissue rather than nonliving
surfaces)citation needed. They are non-corrosive, but can be a fire hazard. They also have limited residual activity
due to evaporation, which results in brief contact times unless the surface is submerged, and have a limited
activity in the presence of organic materialcitation needed. Alcohols are most effective when combined with purified
water to facilitate diffusion through the cell membrane; 100% alcohol typically denatures only external
membrane proteins.11 A mixture of 70% ethanol or isopropanol diluted in water is effective against a wide
spectrum of bacteria, though higher concentrations are often needed to disinfect wet surfaces.12 Additionally,
high-concentration mixtures (such as 80% ethanol + 5% isopropanol) are required to effectively inactivate lipidenveloped viruses (such as HIV, hepatitis B, and hepatitis C).121314 High concentrations of alcohol or solvents or
combination with other disinfectants can result in drying out much more quickly on the applied surface. citation
needed
Such drying could lead to cyst formation and thus ineffective or incomplete disinfection citation needed. Alcohol
is, at best, only partly effective against most non-enveloped viruses (such as hepatitis A)citation needed, and is not
effective against fungal and bacterial sporescitation needed.1113 The efficacy of alcohol is enhanced when in solution
with the wetting agent dodecanoic acid (coconut soap). The synergistic effect of 29.4% ethanol with
dodecanoic acid is effective against a broad spectrum of bacteria, fungi, and viruses. Further testing is being
performed against Clostridium difficile (C.Diff) spores with higher concentrations of ethanol and dodecanoic
acid, which proved effective with a contact time of ten minutes.
20 marks
1.Metabolism
Metabolism (from Greek: μεταβολή metabolē, "change" or Greek: μεταβολισμός metabolismos, "outthrow") is
the set of life-sustaining chemical transformations within the cells of living organisms. 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 all chemical reactions that occur in living organisms, including digestion
and the transport of substances into and between different cells, in which case the set of reactions within the
cells is called intermediary metabolism or intermediate metabolism.
Metabolism is usually divided into two categories. Catabolism, that breaks down organic matter and harvests
energy by way of cellular respiration, andanabolism that uses energy to construct components of cells such
as proteins and nucleic acids.
The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is
transformed through a series of steps into another chemical, by a sequence of enzymes. 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 that
allow the reactions to proceed more rapidly. Enzymes also allow the regulation of metabolic pathways in
response to changes in the cell's environment or tosignals from other cells.
The metabolism 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.1 The speed of metabolism, the metabolic rate, influences how much food an organism will require,
and also affects how it is able to obtain that food.
A striking feature of metabolism is the similarity of the basic metabolic pathways and components between
even vastly different species.2 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 multicellularorganisms like elephants.3 These striking
similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and retained
because of their efficacy.45
Key biochemicals
Most of the structures that make up animals, plants and microbes are made from three basic classes
of molecule: amino acids, carbohydratesand lipids (often called fats). As these molecules are vital for life,
metabolic reactions either focus on making these molecules during the construction of cells and tissues, or by
breaking them down and using them as a source of energy, by their digestion. These biochemicals can be
joined together to make polymers such as DNA and proteins, essential macromolecules of life.
Amino acids and proteins
Proteins are made of amino acids arranged in a linear chain joined together by peptide bonds. Many proteins
are enzymes that catalyze the chemical reactions in metabolism. Other proteins have structural or mechanical
functions, such as those that form the cytoskeleton, a system ofscaffolding that maintains the cell
shape.6 Proteins are also important in cell signaling, immune responses, cell adhesion, active transport across
membranes, and the cell cycle.7 Amino acids also contribute to cellular energy metabolism by providing a
carbon source for entry into the citric acid cycle (tricarboxylic acid cycle),8 especially when a primary source of
energy, such asglucose, is scarce, or when cells undergo metabolic stress.9
Lipids
Lipids are the most diverse group of biochemicals. Their main structural uses are as part of biological
membranes both internal and external, such as the cell membrane, or as a source of energy.7 Lipids are
usually defined as hydrophobic or amphipathic biological molecules but will dissolve in organic solvents such
as benzene or chloroform.10 The fats are a large group of compounds that contain fatty acids and glycerol; a
glycerol molecule attached to three fatty acid esters is called a triacylglyceride.11 Several variations on this
basic structure exist, including alternate backbones such as sphingosine in the sphingolipids,
and hydrophilic groups such as phosphate as in phospholipids. Steroids such as cholesterol are another major
class of lipids.12
Carbohydrates
Carbohydrates are aldehydes or ketones, with many hydroxyl groups attached, that can exist as straight chains
or rings. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the
storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in
animals).7 The basic carbohydrate units are called monosaccharides and include galactose, fructose, and most
importantly glucose. Monosaccharides can be linked together to form polysaccharides in almost limitless
ways.13
Nucleotides
The two nucleic acids, DNA and RNA are polymers of nucleotides, each nucleotide composed of a phosphate
group, a ribose sugar group, and anitrogenous base. Nucleic acids are critical for the storage and use of
genetic information, and its interpretation through the processes of transcriptionand protein biosynthesis.7 This
information is protected by DNA repair mechanisms and propagated through DNA replication.
Many viruses have anRNA genome, for example HIV, which uses reverse transcription to create a DNA
template from its viral RNA genome.14 RNA in ribozymes such asspliceosomes and ribosomes is similar to
enzymes as it can catalyze chemical reactions. Individual nucleosides are made by attaching a nucleobaseto
a ribose sugar. These bases are heterocyclic rings containing nitrogen, classified as purines or pyrimidines.
Nucleotides also act as coenzymes in metabolic group transfer reactions.15
Coenzymes
Structure of the coenzyme acetyl-CoA.The transferableacetyl group is bonded to the sulfur atom at the extreme left.
Main article: Coenzyme
Metabolism involves a vast array of chemical reactions, but most fall under a few basic types of reactions that
involve the transfer offunctional groups.16 This common chemistry allows cells to use a small set of metabolic
intermediates to carry chemical groups between different reactions.15 These group-transfer intermediates are
called coenzymes. Each class of group-transfer reactions is carried out by a particular coenzyme, which is
the substrate for a set of enzymes that produce it, and a set of enzymes that consume it. These coenzymes are
therefore continuously made, consumed and then recycled.17
One central coenzyme is adenosine triphosphate (ATP), the universal energy currency of cells. This nucleotide
is used to transfer chemical energy between different chemical reactions. There is only a small amount of ATP
in cells, but as it is continuously regenerated, the human body can use about its own weight in ATP per
day.17 ATP acts as a bridge between catabolism and anabolism, with catabolic reactions generating ATP and
anabolic reactions consuming it. It also serves as a carrier of phosphate groups in phosphorylation reactions.
A vitamin is an organic compound needed in small quantities that cannot be made in the cells. In
human nutrition, most vitamins function as coenzymes after modification; for example, all water-soluble
vitamins are phosphorylated or are coupled to nucleotides when they are used in cells.18 Nicotinamide adenine
dinucleotide (NAD+), a derivative of vitamin B3 (niacin), is an important coenzyme that acts as a hydrogen
acceptor. Hundreds of separate types of dehydrogenases remove electrons from their substrates
and reduce NAD+ into NADH. This reduced form of the coenzyme is then a substrate for any of
the reductases in the cell that need to reduce their substrates.19 Nicotinamide adenine dinucleotide exists in
two related forms in the cell, NADH and NADPH. The NAD+/NADH form is more important in catabolic
reactions, while NADP+/NADPH is used in anabolic reactions.
2.Antiseptic
From Wikipedia, the free encyclopedia
Antiseptics (from Greek ἀντί: anti, '"against"1 + σηπτικός: sēptikos, "putrefactive"2) are antimicrobial
substances that are applied to living tissue/skin to reduce the possibility of infection,sepsis, or putrefaction.
Antiseptics are generally distinguished from antibiotics by the latter's ability to be transported through
the lymphatic system to destroy bacteria within the body, and fromdisinfectants, which destroy microorganisms
found on non-living objects.
Some antiseptics are true germicides, capable of destroying microbes (bacteriocidal), while others
are bacteriostatic and only prevent or inhibit their growth.
Antibacterials are antiseptics that have the proven ability to act against bacteria. Microbicides which destroy
virus particles are called viricides or antivirals.

Usage in surgery
Joseph Lister
The widespread introduction of antiseptic surgical methods followed the publishing of the paper Antiseptic
Principle of the Practice of Surgery in 1867 by Joseph Lister, inspired by Louis Pasteur's germ theory of
putrefaction. In this paper, Lister advocated the use of carbolic acid (phenol) as a method of ensuring that any
germs present were killed. Some of this work was anticipated by:

Ancient Greek physicians Galen (circa 130–200 ) and Hippocrates (circa 400 BC) and Sumerian clay
tablets dating from 2150 BC that advocate the use of similar techniques.3

Medieval surgeons Hugo of Lucca, Theoderic of Servia, and his pupil Henri de Mandeville were opponents
of Galen's opinion that pus was important to healing, which had led ancient and medieval surgeons to let
pus remain in wounds. They advocated draining and cleaning wound lips with wine, dressing the wound
after suturing it if necessary, and leaving the dressing on for ten days, soaking it in warm wine all the while,
before changing it. Their theories were bitterly opposed by Galenist Guy de Chauliac and others trained in
the classical tradition.4

Joseph Smith, Jr., alluded to the use of alcohol as an antiseptic in February 1833, when he wrote what is
now section 89 of the Doctrine and Covenants, popularly known as the "Word of Wisdom". Specifically,
verse 7 states: "And, again, strong drinks are not for the belly, but for the washing of your bodies."5

Oliver Wendell Holmes, Sr., who published The Contagiousness of Puerperal Fever in 1843

Florence Nightingale, who contributed substantially to the report on the Royal Commission on the Health
of the Army (1856–1857), based on her earlier work

Ignaz Semmelweis, who published his work The Cause, Concept and Prophylaxis of Childbed Fever in
1861, summarizing experiments and observations since 18476

George H. Tichenor, who experimented with the use of alcohol on wounds circa 1861–1863 during
the American Civil War
Functionality
Bacterial growth requires a food supply, moisture, oxygen (if the bacteria are obligate aerobes), and a certain
minimum temperature (see bacteriology). These conditions have been studied and dealt with in food
preservation and the ancient practice of embalming the dead, which is the earliest known systematic use of
antiseptics.
In early inquiries before microbes were understood, much emphasis was given to the prevention of
putrefaction, and procedures were carried out to determine the amount of agent that must be added to a given
solution to prevent the development of pus and putrefaction; however, due to a lack of a developed
understanding of germ theory, this method was inaccurate and, today, an antiseptic is judged by its effect on
pure cultures of a defined microbe and/or its vegetative and spore forms. The standardization of antiseptics has
been implemented in many instances, and a water solution of phenol of a certain fixed strength is now used as
the standard to which other antiseptics are compared.
3.Bactericide
From Wikipedia, the free encyclopedia
(Redirected from Bacteriocidal)
A bactericide or bacteriocide, sometimes abbreviated Bcidal, is a substance that kills bacteria. Bactericides
are disinfectants, antiseptics, or antibiotics.1
Bactericidal disinfectants
The most used disinfectants are those applying

active chlorine (i.e., hypochlorites, chloramines, dichloroisocyanurate and trichloroisocyanurate, wet
chlorine, chlorine dioxide, etc.),

active oxygen (peroxides, such as peracetic acid, potassium persulfate, sodium perborate, sodium
percarbonate, and urea perhydrate),

iodine (iodpovidone (povidone-iodine, Betadine), Lugol's solution, iodine tincture, iodinated nonionic
surfactants),

concentrated alcohols (mainly ethanol, 1-propanol, called also n-propanol and 2-propanol,
called isopropanol and mixtures thereof; further, 2-phenoxyethanol and 1- and 2-phenoxypropanolsare
used),

phenolic substances (such as phenol (also called "carbolic acid"), cresols (called "Lysole" in combination
with liquid potassium soaps), halogenated (chlorinated, brominated) phenols, such
as hexachlorophene, triclosan, trichlorophenol, tribromophenol, pentachlorophenol, Dibromol and salts
thereof),

cationic surfactants, such as some quaternary ammonium cations (such as benzalkonium chloride, cetyl
trimethylammonium bromide or chloride, didecyldimethylammonium chloride,cetylpyridinium
chloride, benzethonium chloride) and others, non-quaternary compounds, such
as chlorhexidine, glucoprotamine, octenidine dihydrochloride etc.),

strong oxidizers, such as ozone and permanganate solutions;

heavy metals and their salts, such as colloidal silver, silver nitrate, mercury chloridedisambiguation
needed
, phenylmercury salts, copper sulfate, copper oxide-chloride etc. Heavy metals and their salts are the
most toxic and environment-hazardous bactericides and therefore their use is strongly discouraged or
prohibited

properly concentrated strong acids (phosphoric, nitric, sulfuric, amidosulfuric, toluenesulfonic acids) and

alkalis (sodium, potassium, calcium hydroxides), such as of pH < 1 or > 13, particularly under elevated
temperature (above 60°C), kills bacteria.
Bactericidal antiseptics
As antiseptics (i.e., germicide agents that can be used on human or animal body, skin, mucoses, wounds and
the like), few of the above mentioned disinfectants can be used, under proper conditions (mainly concentration,
pH, temperature and toxicity toward humans and animals). Among them, some important are

properly diluted chlorine preparations (f.e. Daquin's solution, 0.5% sodium or potassium hypochlorite
solution, pH-adjusted to pH 7 – 8, or 0.5 – 1% solution of sodium benzenesulfochloramide (chloramine B)),
some

iodine preparations, such as iodopovidone in various galenics (ointment, solutions, wound plasters), in the
past also Lugol's solution,

peroxides such as urea perhydrate solutions and pH-buffered 0.1 – 0.25% peracetic acid solutions,

alcohols with or without antiseptic additives, used mainly for skin antisepsis,

weak organic acids such as sorbic acid, benzoic acid, lactic acid and salicylic acid

some phenolic compounds, such as hexachlorophene, triclosan and Dibromol, and

cation-active compounds, such as 0.05 – 0.5% benzalkonium, 0.5 – 4% chlorhexidine, 0.1 – 2% octenidine
solutions.
Others are generally not applicable as safe antiseptics, either because of their corrosive or toxic nature.
4.Sodium azide
Sodium azide is the inorganic compound with the formula NaN3. This colorless salt is the gas-forming
component in many car airbag systems. It is used for the preparation of other azide compounds. It is
an ionic substance, is highly soluble in water, and is very acutely toxic.

Structure and preparation
Sodium azide is an ionic solid. Two crystalline forms are known, rhombohedral and hexagonal.23 The azide
anion is very similar in each, beingcentrosymmetric with N–N distances of 1.18 Å. The Na+
ion is pentacoordinated.
The common synthesis method is the "Wislicenus process," which proceeds in two steps from ammonia. In the
first step, ammonia is converted tosodium amide:
2 Na + 2 NH3 → 2 NaNH2 + H2
The sodium amine is subsequently combined with nitrous oxide:
2 NaNH2 + N2O → NaN3 + NaOH + NH3
Alternatively the salt can be obtained by the reaction of sodium nitrate with sodium amide.4
Applications
Automobile airbags and airplane escape chutes
Older airbag formulations contained mixtures of oxidizers and sodium azide and other agents
including ignitors and accelerants. An electronic controller detonates this mixture during an automobile
crash:
2 NaN3 → 2Na + 3 N2
The same reaction occurs upon heating the salt to approximately 300 °C. The sodium that is
formed is a potential hazard itself and, in automobile airbags, it is converted by reaction with other
ingredients, such as potassium nitrate and silica. In the latter case, innocuous sodium silicates
are generated.5 Sodium azide is also used in airplane escape chutes. Newer generation air bags
contain nitroguanidine or similar less sensitive explosives.
Organic and inorganic synthesis
Due to its explosion hazard, sodium azide is of only limited value in industrial scale organic
chemistry. In the laboratory, it is used in organic synthesis to introduce the azide functional group
by displacement of halides. The azide functional group can thereafter be converted to
an amine by reduction with either lithium aluminium hydride or a tertiary phosphine such
as triphenylphosphine in the Staudinger reaction, with Raney nickel or with hydrogen sulfide in
pyridine.
Iron aziderecursor to other inorganic azide compounds, e.g. lead azide and silver azide, which
are used in explosives.
Biochemistry and biomedical uses
Sodium azide is a useful probe reagent, mutagen, and preservative. In hospitals and laboratories,
it is a biocide; it is especially important in bulk reagents and stock solutions which may otherwise
support bacterial growth where the sodium azide acts as a bacteriostatic by inhibiting cytochrome
oxidase in gram-negative bacteria; gram-positive (streptococci, pneumococci, lactobacilli) are
intrinsically resistant.6 It is also used in agriculture for pest control.
Azide inhibits cytochrome oxidase by binding irreversibly to the heme cofactor in a process
similar to the action of carbon monoxide. Sodium azide particularly affects organs that undergo
high rates of respiration, such as the heart and the brain.citation needed
Reactions
Treatment of sodium azide with strong acids gives hydrazoic acid, which is also extremely toxic:
H+
+ N−
3
→ HN
3
Aqueous solutions contain minute amounts of hydrogen azide, as described by the following
equilibrium:
N−
3
+H
2O
3
HN
+ OH−
(K = 10−4.6
)
Sodium azide can be destroyed by treatment with nitrous acid solution:7
2 NaN3 + 2 HNO2 → 3 N2 + 2 NO + 2 NaOH
Safety considerations
Sodium azide is a severe poison. It may be fatal in contact with skin or if swallowed.
Even minute amounts can cause symptoms. The toxicity of this compound is
comparable to that of soluble alkali cyanides and the lethal dose for an adult human
is about 0.7 grams.8 No toxicity has been reported from spent airbags.9