The Basics of Bio-Inorganic Chemistry: An Overview
A Brief Introduction to Bioinorganic Chemistry
Bioinorganic chemistry is the branch of chemistry that deals with the chemical reactions involved in the life processes of living organisms. Initially, it was believed that studying carbon-containing compounds and molecules with carbon-hydrogen bonds would be sufficient to comprehend all life-related chemical reactions. However, it was later discovered that inorganic elements, particularly metal ions, play a crucial role in numerous biological processes. Without the involvement of suitable metal ions, enzyme-catalysed biochemical reactions would proceed at a significantly slower rate. It is where the study of bioinorganic chemistry becomes indispensable. This blog article "A brief introduction to bioinorganic chemistry" explians the definition, classification, and importance of bioinorganic chemistry.
Table of contents
What is bioinorganic chemistry?
Bioinorganic chemistry is a branch of chemistry that focuses
on comprehensively studying the structure, occurrence, abundance, and
biological significance of inorganic elements in relation to various life
processes.
Research has shown that approximately 35-40 inorganic
elements play a crucial role in the biological processes of living organisms.
Over time, bioinorganic chemistry has evolved into a
multidisciplinary field, drawing upon the foundations of medicinal chemistry, biochemistry,
microbiology, and crystallography.
Role of bioinorganic elements in biological processes
Bioinorganic elements play a crucial role in supporting the
growth and metabolic activities of living organisms, especially in energy
production.
Metal ions, acting as catalysts, effectively regulate
electron flow in enzyme-catalysed reactions. Consequently, numerous enzymes
rely on metal ions for their functionality.
Certain processes have specific requirements for metal ions, where only particular metal ions in specific oxidation states can meet the necessary catalytic or structural criteria. For example- Ca2+ ions are required to maintain the regular beating of the heart.
These bioinorganic elements also serve multiple purposes,
including substrate binding and orientation with respect to functional groups in
the active site, as well as facilitating redox activity in metals with multiple
valence states.
(a) Energy sources for life: (Photosynthetic processes)
We all recognize the importance of energy for sustaining life. Green plants utilize sunlight in the process of photosynthesis to produce carbohydrates, which are subsequently oxidized to release energy. Therefore, two fundamental chemical processes are integral to the chemistry of life.
- The absorption of radiant solar energy enables the production of oxygen and reduced organic compounds (such as glucose) from carbon dioxide and water.
- The oxidation of the aforementioned reduced organic substances results in the formation of carbon dioxide, water, and energy.
Living systems can attain thermodynamic equilibrium by
burning their reducing sugars with the release of energy.
Metal-containing enzymes are crucial in energy transfer
reactions involving oxygen transport to the site of oxidation, and subsequent
redox reactions.
Certain living organisms rely solely on simple diffusion for
oxygen transport, lacking any specialized oxygen transport system.
However, there are organisms such as certain worms and
lower-level life forms that possess oxygen transport mechanisms facilitated by
hemoproteins, nonheme iron proteins, and copper-containing proteins.
(b) Energy sources for life: (Non-photosynthetic processes)
Most living organisms depend on photosynthesis to capture
solar energy, either directly through green plants or indirectly through
saprophytes and animals.
However, there are a
few complex biochemical systems that allow certain organisms to obtain energy
through inorganic processes.
Chemolithotrophic bacteria, specifically iron bacteria,
generate energy through the oxidation of iron (II) compounds.
In contrast, nitrifying bacteria produce energy by oxidizing
either ammonia or nitrite ions.
On the other hand, sulfur bacteria derive energy through the
oxidation of different forms of sulfur.
The aforementioned sulfur bacteria reaction closely resembles
photosynthesis, with the exception that sulfur, rather than chlorophyll, serves
as the electron source for the reduction of water to carbohydrate.
Classification of bioinorganic elements according to their action in biological system
Life developed by utilizing chemical elements that are
abundant in concentration, while rarely relying on the rare inorganic elements
that are scarce on Earth.
The bioinorganic elements, due to their significance in
regulating life processes, are classified into two categories: essential
elements and trace elements.
Regardless of their importance, it should be recognized that
chemical elements present in excessively high or low concentrations within
living systems can have toxic effects on life. Depending on their adverse
impact on organisms, they can be classified as toxic elements.
Elements that do not contribute positively to regulating the
life processes of biological species are categorized as non-essential elements.
Al, Ti, and Zr are some examples.
However, determining the precise concentration of elements
that are harmful to organisms is challenging, as the chemical properties of
these inorganic elements remain constant while biological systems and their
requirements vary over time.
What are the essential elements in bioinorganic chemistry?
Essential elements are vital for carrying out life processes
in living beings, whether required in large or small quantities.
Life originated relying on elements that were abundant in
concentration but became toxic at higher levels, eventually becoming essential
elements.
Examples of essential elements include metals like Sodium,
Potassium, Magnesium, and Calcium, as well as non-metals like Carbon, Nitrogen,
Hydrogen, Oxygen, Chlorine, and Phosphorus.
Carbon, Nitrogen, Hydrogen, and Oxygen are major components
of our food, present in proteins, carbohydrates, and lipids.
Additionally, some elements in our food are needed in
quantities greater than 1 mg. These include Sodium, Potassium, Magnesium,
Calcium, Phosphorus, Sulfur, and Chlorine. They are referred to as macro
nutrients or principle elements, constituting 60-80% of the body's inorganic
elements.
Here are the biological functions of some essential
elements:
Iodine: It plays a crucial role in many organisms. It is
involved in growth regulation, metabolism, and amphibian metamorphosis,
primarily through its association with thyroxine.
Copper: It is essential for all organisms. Copper is a
component of hemocyanin and redox enzymes, contributing to important biological
processes.
Magnesium: Found in all chlorophylls, magnesium serves
multiple functions in organisms. It activates enzymes and plays a role in
electrochemical processes.
Calcium: Found in all organisms, calcium plays a vital role
in various functions. It is involved in blood clotting, contributes to
electrochemical processes, and serves as a structural component in bones, cell
walls, and shells.
Molybdenum: Despite its lower concentration in marine
animals compared to land animals (about 1-2 ppm), molybdenum is an essential
trace element. It is required by all organisms except green algae. Molybdenum
is utilized in enzymes associated with nitrate reduction and nitrogen fixation.
What are the trace elements in bioinorganic chemistry?
Trace elements are essential elements that are required in
low concentrations, typically ranging from 50 ppb to 1 ppm. However, they can
be toxic at higher levels beyond this ultratrace range. Examples of trace
elements include Nickel, Arsenic, and Cadmium.
Although the precise biological functions of these elements
are not fully defined, they are found to be beneficial for various life
processes in organisms.
Here are the biological functions of some trace elements
Nickel: It plays an important role as an active metal in
plant ureases and hydrogenases. Deficiency of nickel can lead to impaired liver
function and morphology in rats and chicks.
Arsenic: It is beneficial for the health of goats, pigs,
rats, and humans. Deficiency of arsenic can result in increased mortality and
depressed growth.
Cadmium: The exact biological importance of cadmium is not
well understood, but it is present in very low concentrations as an ultratrace
element in rats.
Iron is found in heme derivatives, while Zinc is found in
enzymes such as carboxypeptidase and carbonic anhydrase. The classification of
these elements as trace elements may vary, as determining the essentiality of inorganic
substances in living organisms is challenging.
On the other hand, certain elements are considered trace
elements even if their specific biological roles are not clearly defined, but
they have been found to be useful.
For instance, sea squirts have the ability to concentrate
vanadium from sea water by a million-fold, yet its biological function remains
elusive.
Techniques like atomic absorption, X-ray fluorescence,
atomic fluorescence, and activation analysis are employed to measure the
concentration of ultratrace elements, which are typically less than 1 ppm.
Geo-chemical effect on the distribution of metals
The number of elements that play a crucial role in
biological processes is significantly smaller compared to the total number of
118 discovered elements.
This is primarily due to their availability based on natural
abundance. For example, Molybdenum, despite being the heaviest metal, has a
concentration of only 0.0015 g kg-1 in the Earth's crust, while
Iodine, the heaviest non-metal, has a concentration of 0.0005 g kg-1.
However, both these elements have recognized biological importance.
Similarly, the less abundant elements in the first
transition series are found to be more important in enzymes compared to
abundant elements like Sodium (Na), Potassium (K), Magnesium (Mg), Calcium
(Ca), Carbon (C), Nitrogen (N), and Phosphorus (P).
| Table-1: Comparison of concentration of bioinorganic elements | |
|---|---|
| Name of macronutrient elements | Concentration in g/Kg on earth crust |
| Na | 24 |
| Mg | 20 |
| K | 24 |
| Ca | 42 |
| Name of first transition series elements | Concentration in g/Kg on earth crust |
| Sc | 0.22 |
| V | 0.135 |
| Cr | 0.1 |
| Mn | 0.95 |
Therefore, two factors that assist in determining the
suitability of an element for a specific biological function are its natural
abundance and its chemical interaction with biological systems.
For instance, elements such as Lead (Pb), Cadmium (Cd), and
Mercury (Hg) are considered toxic due to their low natural abundance, which
makes them rarely available in living systems.
On the other hand, abundant elements like Aluminium (Al),
Titanium (Ti), and Zirconium (Zr) are deemed non-essential because they tend to
form insoluble oxides at biologically relevant pH levels.
Importance of bioinorganic chemistry
1. Studying the role of inorganic elements in
biological processes allows us to identify the specific metal ions responsible
for particular biological activities and understand their adverse effects in
cases of deficiency or excessive intake.
For instance, sodium is predominantly present as Na+
in extracellular fluids. Sodium deficiency leads to muscle cramps, while
excessive sodium intake can result in high blood pressure.
Despite the complexity of biochemical molecules, techniques
such as Electron Paramagnetic Resonance (EPR) spectroscopy aid in studying
metal ions within living systems.
2. Inorganic elements are integral components of
metalloenzymes, metalloproteins, vitamins, hormones, and nucleic acids.
Studying the inorganic substances such as metal ions and coordination compounds
essential for the survival of organisms provides insights into their intricate
mechanisms.
This is because many enzymes and metabolites are metal
complexes, functioning primarily as metal complexes in the majority of cases.
3.
Bioinorganic chemistry is of utmost importance in medical chemistry as it aids
in the discovery of life-saving drugs.
By studying bioinorganic chemistry, researchers can uncover
potential treatments for life-threatening diseases, as a significant number of
medications rely on inorganic molecules.
For instance, inorganic molecules are employed in the
development of drugs for conditions such as cancer, pernicious anemia, and
Alzheimer's disease.
FAQs on bioinorganic chemistry introduction
1. Write some examples of bioinorganic chemistry?
Bioinorganic chemistry exemplifies itself through various
biological processes that involve complex metal ions.
One notable example is the transamination process, which
entails the exchange of functional groups and relies on the pyridoxal (Fe2+/Cu2+
complex) coenzyme.
Additionally, the functioning of chlorophyll in
photosynthesis heavily depends on the Mg2+ complex.
Similarly, in storage and transfer reactions, such as those
involving hemoglobin, the Fe complex is utilized.
2. What are essential and trace elements in biological
processes?
Essential elements play a crucial role in the biological processes of living organisms and are categorized as macronutrients and micronutrients based on their required quantities.
Macronutrients are inorganic elements that are needed in larger amounts by the human body to support various biological processes. For example, calcium serves as a major structural component in bones and cell walls, with concentrations ranging from 1000-1100 grams depending on body weight.
On the other hand, micronutrients are required in smaller quantities to fulfill specific biological functions. Copper, for instance, is a constituent of hemocyanin and redox enzymes and is present in the human body at an approximate concentration of 0.11 grams.
In contrast, trace elements are essential for biological processes, but their precise biological functions are not fully understood due to the complexity of biomolecules.
However, their deficiency can have severe
consequences for organisms. Examples of trace elements include boron, arsenic,
nickel, and tin.
3. What are the non-essential elements in bioinorganic
chemistry?
It is worth noting that out of the 119 chemical elements discovered thus far, not all of them have been found to play a vital role in regulating biological processes.
Inorganic elements that are deemed non-essential to living organisms, meaning they are not required for normal physiological functions, and do not cause harm to the living world even at moderate concentrations, are referred to as non-essential elements.
Examples of non-essential elements include aluminium, barium, strontium, and zirconium. These elements may be present in the environment or biological systems but are not necessary for sustaining life or carrying out essential biological functions.
Know your understanding
1. Which metal ion is necessary for photosynthesis to occur?
- Ca2+
- Co2+
- Mn3+
- Mg2+
Answer: Mg2+
2. Which of the following is an example of non-essential element?
- Zn
- Zr
- S
- Cl
Answer: Zr
3. Which technique is employed to quantify the concentration of an element below 1 ppm?
- Spin magnetic spectroscopy
- Titrimetric analysis
- X-ray fluorescence
- Precipitation reactions
Answer: X-ray fluorescence
4. Which of the following element is a macronutrient?
- Arsenic
- Lead
- Potassium
- Selenium
Answer: Potassium
5. Which of the following functions are performed by the metal ion?
- Transportation of Oxygen
- Participate in enzyme-catalysed reactions
- Engage in growth and metabolic activitites
- All the above
Answer: All the above