The chemical term earths was historically applied to certain chemical
substances, once thought to be elements, and this name was borrowed from one of the
four classical elements of Plato. "Earths" later turned out to be chemical compounds,
albeit difficult to concentrate, such as rare earths and alkaline earths.
Earths are metallic oxides, and the corresponding metals were classified into
the corresponding groups: rare earth metals and alkaline earth metals
Let’s take a moment for a closer look at the Earth’s chemistry; in particular, the
chemical elements interspersed in the Earth’s major depths.
With an atmosphere containing 78% nitrogen and 21% oxygen, the Earth is the
only planet in the solar system capable of initiating and sustaining life-forms; the
various chemical elements that make up the Earth, from the crust, down to the mantle
and core, have a little something to do with that.
Defining the Earth’s Boundaries and Elements
As scientists are not able to visit the Earth’s deep interior or place instruments
within it, they explore in subtle ways. One approach is to study the Earth with non-
material probes, such as seismic waves emitted by earthquakes. As seismic waves
pass through the Earth, they undergo sudden changes in direction and velocity at
certain depths. These depths mark the major boundaries, also called discontinuities,
that divide the Earth into crust, mantle and core.
The Crust. The Earth’s crust is the thin outermost layer of the Earth, with an
average depth of 24 km (15 mi). The crust accounts for 1.05% of the Earth’s volume
and 0.5% of its mass. The chemical elements oxygen, silicon and aluminum dominate
the crustal composition. The major mineral type – the feldspars – are alumino-
silicates of the alkali and alkaline-earth metals. Silicon dioxide is the second most
about 2865 km (1780 mi) thick, occupying about 82.5% of the Earth’s volume. The
upper mantle is rich in olivine and pyroxenes. The major mineral type in the lower
mantle appears to be pyroxenes, especially magnesium silicate. Scientists think that
the lowest layer of the mantle called “D layer” is richer in aluminum and calcium
than the higher layers of the mantle.
The Core. The core extends from the base of the mantle to the Earth’s center,
and is 6964 kn (4327 mi) in diameter – accounting for only 16.3% of the Earth’s
volume, but 33.5% of its mass. The core is made up of two distinct parts – a liquid
outer core, which is 2260 km (1404 mi) thick, and a solid inner core, which has a
radius of 1222 km (759 mi). The core is chemically distinct from the mantle and
contains about 89% iron and 6% nickel. The remaining 5% is made of lighter
elements, possibly sulfur – but we cannot rule out the presence of oxygen and silicon,
in light of a 2013 study published in Nature, which calls them “prime candidates” for
the lighter elements in the Earth’s core.
As we celebrate Earth Day, and as in recent times, emphasis has been given to
environmental awareness or the value of “green.” This year, let’s pay attention to all
the other colors of Earth as well – the colors we see through chemistry.
Chemistry of Carbon and Its Compounds
Atomic Number: 6
Electronic configuration: 2, 4
Valence electrons: 4
Abundance: Carbon is the 4th most abundant substance in universe and 15th
most abundant substance in the earth’s crust.
Compounds having carbon atoms among the components are known as carbon
compounds. Previously, carbon compounds could only be obtained from a living
source; hence they are also known as organic compounds.
Bonding In Carbon: Covalent Bond
Bond formed by sharing of electrons is called covalent bond. Two of more
atoms share electrons to make their configuration stable. In this type of bond, all the
atoms have similar rights over shared electrons. Compounds which are formed
because of covalent bond are called COVALNET COMPOUNDS.
Covalent bonds are of three types: Single, double and triple covalent bond.
Single Covalent Bond: Single covalent bond is formed because of sharing of
two electrons, one from each of the two atoms.
Formation of hydrogen molecule (H
Atomic Number of H = 1
Electronic configuration of H = 1
Valence electron of H = 1
Hydrogen forms a duet, to obtain stable configuration. This configuration is
similar to helium (a noble gas).
Since, hydrogen has one electron in its valence shell, so it requires one more
electron to form a duet. So, in the formation of hydrogen molecule; one electron from
each of the hydrogen atoms is shared.
Formation of hydrogen chloride (HCl):
Atomic number of chlorine = 17
Electronic configuration of chlorine: 2, 8, 7
Electrons in outermost orbit = 7
Valence electron = 7
Formation of chlorine molecule (Cl
Formation of water (H
Atomic number of oxygen = 8
Electronic configuration of oxygen = 2, 6
Valence electron = 6
Oxygen in water molecule completes stable configuration by the sharing one
Formation of Methane (CH
Valence electron of carbon = 4
Formation of Ethane (C
two from each of the two atoms.
Formation of oxygen molecule (O
In the formation of oxygen molecule, two electrons are shared by each of the
In oxygen, the total number of shared electrons is four, two from each of the
oxygen atoms. So a double covalent bond is formed.
Formation of Carbon dioxide (CO
Valence electron of oxygen = 6
In carbon dioxide two double covalent bonds are formed.
Valence electron of hydrogen = 1
Triple Covalent Bond: Triple covalent bond is formed because of the sharing of
Formation of Nitrogen (N
Electronic configuration of nitrogen = 2, 5
Valence electron = 5
In the formation of nitrogen, three electrons are shared by each of the nitrogen
Formation of Acetylene (C
Properties of Covalent Bond:
Intermolecular force is smaller.
Covalent bonds are weaker than ionic bond. As a result, covalent compounds
particles are formed in covalent bond.
Since, carbon compounds are formed by the formation of covalent bond, so
conductor of electricity.
5.1 Biochemistry, sometimes called biological chemistry, is the study of
information flow through biochemical signaling and the flow of chemical energy
through metabolism, biochemical processes give rise to the complexity of life. Over
the last decades of the 20th century, biochemistry has become so successful at
explaining living processes that now almost all areas of the life sciences from botany
to medicine to genetics are engaged in biochemical research.
Today, the main focus
processes that occur within living cells,
which in turn relates greatly to the study
Biochemistry is closely related to molecular biology, the study of the molecular
mechanisms by which genetic information encoded inDNA is able to result in the
processes of life.
Depending on the exact definition of the terms used, molecular
which to investigate and study molecular biology.
Much of biochemistry deals with the structures, functions and interactions of
biological macromolecules, such as proteins, nucleic acids, carbohydrates and lipids,
which provide the structure of cells and perform many of the functions associated
The chemistry of the cell also depends on the reactions of smaller
organic, for example the amino acids, which are used to synthesize proteins.
reactions are known as metabolism. The findings of biochemistry are applied
primarily in medicine, nutrition, and agriculture. In medicine, biochemists investigate
the causes and cures of diseases.
In nutrition, they study how to maintain health and
soil andfertilizers, and try to discover ways to improve crop cultivation, crop storage
and pest control.
Biochemistry is the branch of science that explores the chemical processes
within and related to living organisms. It is a laboratory based science that brings
together biology and chemistry. By using chemical knowledge and techniques,
biochemists can understand and solve biological problems.
on what’s happening inside our cells, studying components like proteins, lipids and
organelles. It also looks at how cells communicate with each other, for example
during growth or fighting illness. Biochemists need to understand how the structure
of a molecule relates to its function, allowing them to predict how molecules will
Biochemistry covers a range of scientific disciplines, including genetics,
microbiology, forensics, plant science and medicine. Because of its breadth,
biochemistry is very important and advances in this field of science over the past 100
years have been staggering. It’s a very exciting time to be part of this fascinating area
What do biochemists do?
makers, engineers and many more professionals
Biochemists work in many places, including:
Biochemists have many transferable skills, including:
career opportunities at all levels. The Government recognizes the potential that
developments in biochemistry and the life sciences have for contributing to national
prosperity and for improving the quality of life of the population. Funding for
research in these areas has been increasing dramatically in most countries, and the
biotechnology industry is expanding rapidly.
At its broadest definition, biochemistry can be seen as a study of the
components and composition of living things and how they come together to become
life, and the history of biochemistry may therefore go back as far as the ancient
However, biochemistry as a specific scientific discipline has its beginning
some time in the 19th century, or a little earlier, depending on which aspect of
biochemistry one is being focused on. Some argued that the beginning of
biochemistry may have been the discovery of the first enzyme, diastase (today called
amylase), in 1833 byAnselme Payen,
while others considered Eduard Buchner's
free extracts in 1897 to be the birth of biochemistry.
Some might also point as
its beginning to the influential 1842 work by Justus von Liebig,Animal chemistry, or,
Organic chemistry in its applications to physiology and pathology, which presented a
chemical theory of metabolism,
or even earlier to the 18th century studies on
field who helped to uncover the layers of complexity of biochemistry have been
proclaimed founders of modern biochemistry, for example Emil Fischer for his work
on the chemistry of proteins,
and F. Gowland Hopkins on enzymes and the
The term "biochemistry" itself is derived from a combination of biology and
chemistry. In 1877, Felix Hoppe-Seyler used the term (biochemie in German) as a
synonym for physiological chemistry in the foreword to the first issue of Zeitschrift
the setting up of institutes dedicated to this field of study.
The German chemist
Carl Neuberghowever is often cited to have been coined the word in 1903,
while some credited it to Franz Hofmeister.
DNA structure (1D65)
It was once generally believed that life and its materials had some essential
found in non-living matter, and it was thought that only living beings could produce
the molecules of life.
synthesis of urea, proving that organic compounds can be created artificially.
development of new techniques such as chromatography, X-ray diffraction, dual
polarisation interferometry, NMR spectroscopy, radioisotopic labeling, electron
microscopy, and molecular dynamics simulations. These techniques allowed for the
discovery and detailed analysis of many molecules and metabolic pathways of the
cell, such as glycolysis and theKrebs cycle (citric acid cycle).
Another significant historic event in biochemistry is the discovery of the gene
and its role in the transfer of information in the cell. This part of biochemistry is often
called molecular biology.
Franklin, and Maurice Wilkins were instrumental in solving DNA structure and
suggesting its relationship with genetic transfer of information.
Beadle and Edward Tatum received the Nobel Prize for work in fungi showing that
one gene produces one enzyme.
convicted of murder with DNA evidence, which led to growth of forensic science.
More recently, Andrew Z. Fire and Craig C. Mello received the2006 Nobel Prize for
Starting materials: the chemical elements of life
The main elements that compose the human body are shown from most
Around two dozen of the 92 naturally occurring chemical elements are
essential to various kinds of biological life. Most rare elements on Earth are not
needed by life (exceptions being selenium and iodine), while a few common ones
(aluminum and titanium) are not used. Most organisms share element needs, but there
are a few differences between plants and animals. For example, ocean algae use
bromine, but land plants and animals seem to need none. All animals require sodium,
but some plants do not. Plants need boron and silicon, but animals may not (or may
need ultra-small amounts).
Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and
phosphorus—make up almost 99% of the mass of living cells, including those in the
human body (see composition of the human body for a complete list). In addition to
the six major elements that compose most of the human body, humans require
smaller amounts of possibly 18 more.
are carbohydrates, lipids, proteins, and nucleic acids.
Many biological molecules
are linked together to create largemacromolecules known as polymers. When
monomers are linked together to synthesize a biological polymer, they undergo a
process calleddehydration synthesis. Different macromolecules can assemble in
larger complexes, often needed for biological activity.
Glucose, a monosaccharide
A molecule of sucrose (glucose +fructose), a disaccharide
Amylose, a polysaccharide made up of several thousand glucose units
Sugars are carbohydrates, but not all carbohydrates are sugars. There are more
carbohydrates on Earth than any other known type of biomolecule; they are used to
store energy and genetic information, as well as play important roles in cell to cell
interactions and communications.
The simplest type of carbohydrate is a monosaccharide, which among other
properties contains carbon, hydrogen, and oxygen, mostly in a ratio of 1:2:1
(generalized formula C
, where n is at least 3). Glucose (C
) is one of the
commonly associated with the sweet taste of fruits,
and deoxyribose (C
form, through a nucleophilic addition reaction between thecarbonyl group and one of
the hydroxyls of the same molecule. The reaction creates a ring of carbon atoms
closed by one bridgingoxygen atom. The resulting molecule has an hemiacetal or
hemiketal group, depending on whether the linear form was an aldose or a ketose.
The reaction is easily reversed, yielding the original open-chain form.
In these cyclic forms, the ring usually has 5 or 6 atoms. These forms are called
furanoses and pyranoses, respectively — by analogy withfuran and pyran, the
simplest compounds with the same carbon-oxygen ring (although they lack the
double bonds of these two molecules). For example, the aldohexose glucose may
form a hemiacetal linkage between the hydroxyl on carbon 1 and the oxygen on
carbon 4, yielding a molecule with a 5-membered ring, called glucofuranose. The
same reaction can take place between carbons 1 and 5 to form a molecule with a 6-
membered ring, called glucopyranose. Cyclic forms with a 7-atom ring (the same of
oxepane), rarely encountered, are called heptoses.
When two monosaccharides undergo dehydration synthesis whereby a
molecule of water is released, as two hydrogen atoms and one oxygen atom are lost
from the two monosaccharides. The new molecule, consisting of two
monosaccharides, is called a disaccharide and is conjoined together by a glycosidic
or ether bond. The reverse reaction can also occur, using a molecule of water to split
up a disaccharide and break the glycosidic bond; this is termed hydrolysis. The most
well-known disaccharide is sucrose, ordinary sugar (in scientific contexts, called
table sugar or cane sugar to differentiate it from other sugars). Sucrose consists of a
glucose molecule and a fructose molecule joined together. Another important
disaccharide is lactose, consisting of a glucose molecule and a galactose molecule. As
most humans age, the production of lactase, the enzyme that hydrolyzes lactose back
into glucose and galactose, typically decreases. This results in lactase deficiency, also
called lactose intolerance.
When a few (around three to six) monosaccharides are joined, it is called an
oligosaccharide (oligo- meaning "few"). These molecules tend to be used as markers
and signals, as well as having some other uses.
Many monosaccharides joined
or they may bebranched. Two of the most common polysaccharides are cellulose and
glycogen, both consisting of repeating glucose monomers. Examples are Cellulose
which is an important structural component of plant's cell walls, and glycogen, used
as a form of energy storage in animals.
Sugar can be characterized by having reducing or non-reducing ends. A
reducing end of a carbohydrate is a carbon atom that can be in equilibrium with the
open-chain aldehyde(aldose) or keto form (ketose). If the joining of monomers takes
place at such a carbon atom, the free hydroxy group of the pyranose or furanose form
is exchanged with an OH-side-chain of another sugar, yielding a full acetal. This
prevents opening of the chain to the aldehyde or keto form and renders the modified
residue non-reducing. Lactose contains a reducing end at its glucose moiety, whereas
the galactose moiety form a full acetal with the C4-OH group of glucose. Saccharose
does not have a reducing end because of full acetal formation between the aldehyde
carbon of glucose (C1) and the keto carbon of fructose (C2).