BIOINORGANIC CHEMISTRY
Metal ions present in biological systems, classification of elements according to their action in biological system.
Biological systems contain a wide range of metal ions, including ---
(1) Major ones like sodium (𝑁𝑎+), potassium (𝐾+), calcium (𝐶𝑎2+), magnesium (𝑀𝑔2+), iron (𝐹𝑒), copper (𝐶𝑢), and zinc
(𝑍𝑛),
(2) Trace elements like manganese (𝑀𝑛), cobalt (𝐶𝑜), and molybdenum (𝑀𝑜).
These ions are crucial for numerous functions, such as acting as cofactors in enzymes, transporting molecules, storing
energy, and playing roles in signal transduction.
Major metal ions:
● Sodium and Potassium: Essential for nerve impulse transmission by creating electrochemical gradients across
cell membranes.
● Calcium: Involved in signal transduction, blood clotting, and muscle contraction.
● Magnesium: A cofactor in many enzymes, such as those involved in energy production, and is a component of
chlorophyll.
● Iron: A key component of hemoglobin and myoglobin for oxygen transport, and a cofactor in many enzymes.
● Copper and Zinc: Found in various enzymes and proteins, playing roles in oxidation-reduction reactions and
protein structure.
Other important metal ions:
● Manganese: Involved in photosynthesis and is a component of enzymes like superoxide dismutase.
● Cobalt: Essential for vitamin 𝐵12
● Molybdenum: A cofactor in enzymes those are crucial for nitrogen fixation and other metabolic processes.
● Vanadium: Plays a role in some marine organisms.
Classification of elements according to their action in the biological system
Elements
Essential Trace Non-essential Toxic
O, C, H, N, P I, Fe, Cu, Zn, Mn, Al, Sr, Ba, Sn etc Cd, Pb, Hg
etc
Na, K, Mg, Cl, Co, Mo etc,
Ca, S etc.
I. Essential elements are absolutely essential or necessary for life processes. Trace elements are also
necessary for life processes.
II. Non-essential elements are not essential. If they are absent other elements may serve the same function.
III. Toxic elements disturb the natural functions of the biological system.
METAL IONS IN THE BIOLOGICAL SYSTEM
Metal ions their excess and deficiency
, Concentration of metal ions in human being’s system is controlled within very fine limits. This control is
generally exercised by certain biological complexing agents. The deficiency or excess of metal ions causes
disorder, which leads to various diseases.
Calcium
Calcium is a critical element in all animals and man. The primary dietary source of Ca is milk (65-76%), with
smaller amounts derived from meat, fish and eggs (5-10%). Dietary deficiency of Ca is not a common problem in
nations with high dairy product and protein intake, particularly since normal individuals can regulate intestinal
absorption and renal conservation mechanism with great precision. Hence, human health problems related to
geochemical distribution of Ca, its entry into the human food chain and its bio- availability are relatively uncommon.
Effect of Excess of Ca:
In case of excess of Ca, it comes in to the blood as Ca is rejected by cell and its salts are not soluble. So excess of
Calcium in blood leads to the (i) formation of stones, (ii) hardening of arteries, and (iii)cataracts in the eye.
Role of Ca:
Role in Animal:
• Skeletal structure: Around 99% of the body's calcium is stored in bones and teeth as hydroxyapatite, providing
structural strength and a reserve for other bodily functions.
• Muscle function: Calcium is essential for muscle contraction and relaxation, including the regular beating of the
heart.
• Nerve function: It is crucial for nerve impulse transmission and plays a role in the development and remodeling
of neural cells.
• Blood clotting: Calcium ions are a necessary component in the coagulation cascade, which helps in the efficient
healing of wounds.
• Cell signalling: Calcium acts as a universal second messenger, triggering and regulating a vast array of cellular
activities, from fertilization to cell death.
Roles in plants
• Cell wall stability: Calcium helps to stabilize the cell walls of plants, which is important for their overall growth
and structural integrity.
• Stress response: It plays a role in plant signaling and responses to environmental stresses like drought and salt
stress.
Magnesium
Role : Magnesium, an abundant element in the earth’s crust, is vital to both plant and animal life. Chlorophyll
pigment in plants is a Mg-porphyrin complex. All enzymatic reaction in animals and men that are catalyzed by ATP
require Mg as a cofactor. Oxidative phosphorylation, DNA transcription, RNA function, protein synthesis and critical
cell membrane functions are all dependent upon optimal Mg concentrations. Dietary sources high in Mg include nuts,
sea foods, legumes and vegetables; meat is intermediate in Mg content.
Effect of Excess of Mg:
1. Cardiovascular effects:
• Low blood pressure (hypotension)
• Slowed heart rate (bradycardia)
• Heart block and other arrhythmias
• Cardiac arrest
2. Neurological and neuromuscular effects:
• Lethargy and confusion
• Muscle weakness or paralysis
• Decreased or absent deep tendon reflexes
• Respiratory depression or paralysis
Potassium
An adult human has approximately 140 g K of which >90% is both intracellular and exchangeable (K is the
predominant cation in intracellular water) since muscle contains most of the body’s intracellular water, it also contains
most of the K. Since K is found in most animal and vegetable foods, dietary deficiency is exceedingly rare except
under unusual conditions (such as diets very high in refined sugars, alcoholic individuals deriving most of their
calories from low-K alcoholic beverages in the states of starvation etc.).
Key biological roles of potassium
• Fluid and electrolyte balance: As the primary intracellular ion, potassium maintains the body's fluid balance and
, is a key part of the electrolyte balance with sodium.
• Nerve function: It is essential for the transmission of nerve signals and the maintenance of the electrochemical
gradients necessary for nerve cell function.
• Muscle contraction: Potassium helps stimulate calcium ions to move across the cell membrane, which triggers
muscle cells to contract. It is vital for both skeletal and smooth muscle contractions, including the heart muscle.
• Cellular processes: It is involved in processes like the oxidation of glucose to produce energy (ATP) and activates
many enzymes.
• Heart health: Potassium helps ensure the heart muscle beats regularly. Low potassium levels can lead to abnormal
and irregular heart rhythms.
• Nutrient transport: It helps move nutrients into cells and waste products out of cells.
• Blood pressure regulation: A diet rich in potassium can help offset some of the harmful effects of sodium and
lower blood pressure.
Effect of Excess of K:
In plants:
• Nutrient imbalance: Excess potassium (K) competes with other positively charged nutrients (cations)
such as magnesium (Mg) and calcium (Ca) for absorption by the plant's roots.
• Induced deficiencies: This competition can lead to a deficiency in these other essential nutrients, even if
they are present in the soil, most notably causing magnesium deficiency.
• Leaf Yellowing: A visible sign of induced magnesium deficiency is interveinal chlorosis (yellowing
between the veins) on older leaves.
• Growth impact: These imbalances can limit overall plant growth, stunt development, and reduce fruit
or yield, as seen in both corn and soybean crops.
In animals
• Cardiac issues: In animals, the most serious effect of excess potassium is its impact on the heart.
• Arrhythmias: High potassium can cause cardiac arrhythmias, or irregular heartbeats, notes Wag!.
• Severity: While a veterinarian would likely notice the irregular heartbeat, severe cases can lead to more
obvious symptoms like coughing and fainting.
Sodium
Sodium is the predominant extracellular cation in animals and man. An adult human has about 105 g Na, about
24% is located in bone and about 65% in extracellular water. Sodium ion equilibrium is maintained primarily by the
kidney, the key organ in water and electrolyte balance. Sodium chloride (salt) is the predominant dietary source.
Excess sodium harms plants by causing osmotic stress, making water absorption difficult, and creating ion toxicity
that inhibits photosynthesis and nutrient uptake, leading to stunted growth and wilting. In animals, excess sodium can
lead to dehydration, electrolyte imbalance, and salt toxicity, which can be life-threatening.
Key roles of sodium in the body:
• Nerve impulse transmission: Sodium ions are crucial for transmitting nerve signals throughout the body.
• Fluid and electrolyte balance: Sodium helps maintain the body's overall fluid balance and electrolyte levels, which
is vital for many bodily functions.
• Nutrient transport: It plays a significant role in the transport of sugars and amino acids into cells.
• Heart function: Sodium is necessary for the proper functioning of the heart muscle.
• Muscle contraction: It works with other electrolytes to regulate muscle contraction and relaxation.
• Water regulation: It helps regulate the flow of water across cell membranes.
Effect of Excess sodium:
In plants
• Osmotic stress: High salt concentrations in the soil create a low osmotic potential, making it difficult for plants to
absorb water from the soil.
• Ion toxicity: Excessive sodium ions and chloride ions can be absorbed by the plant, damaging tissues and
interfering with cellular functions.
• Nutrient imbalance: Sodium can outcompete essential nutrients like potassium magnesium, and calcium for
uptake, leading to nutrient deficiencies.
• Photosynthesis reduction: The combination of stress and nutrient deficiency leads to lower rates of
photosynthesis and can impair energy and lipid metabolism.
• Growth inhibition: Excessive sodium reduces leaf expansion, and overall growth, which can lead to plant death.
In animals
• Dehydration: High sodium intake can cause animals to become dehydrated because their bodies are unable to
properly regulate water balance.
, • Electrolyte imbalance: The natural balance of electrolytes in the body is disrupted, affecting normal body
functions.
• Salt toxicosis: In severe cases, the body can no longer cope with the high salt concentration, leading to a
condition known as salt poisoning, which can be fatal.
• Nervous system effects: Sodium is crucial for nerve function, but too much can lead to neurological problems
Cobalt:
Cobalt is an essential element for humans, but its pathway through the food chain to human being remains elusive.
Only a little over 1 mg Co is present in an adult human. In man dietary Co deficiency is only likely among strict
vegetarians or when the intrinsic factor from the stomach that facilitates decreased as in pernicious anaemia.
Key roles of cobalt:
• Vitamin B12 (Cobalamin): Cobalt is the central atom in vitamin B12, a coenzyme necessary for several
enzymes. The active forms, methylcobalamin and adenosylcobalamin, are essential for metabolic processes.
• DNA and protein synthesis: Vitamin B12, and therefore cobalt, is required for the synthesis of DNA and the
production of amino acids and proteins.
• Red blood cell production: Cobalt is essential for the production of red blood cells and can help prevent anemia.
• Nervous system health: It plays a crucial role in the functioning of the nervous system and is involved in
preventing demyelination, which can lead to conditions like multiple sclerosis.
• Metabolism: Cobalt aids in the metabolism of fats and carbohydrates and the conversion of folate into its active
form.
• Plant growth: Cobalt is necessary for the nitrogen-fixing process in leguminous plants, as it is a component of
vitamin B12 required by the symbiotic microbes.
Effect of Excess cobalt:
Effects on plants
• Growth and Development: High levels of cobalt can inhibit growth, reduce biomass, and lead to leaf loss.
• Nutrient Uptake: It can hinder the plant's ability to absorb essential nutrients like iron, leading to iron deficiency
(chlorosis).
• Photosynthesis: Cobalt stress can reduce photosynthetic efficiency and cause ultrastructural damage to
chloroplasts.
• Root Inhibition: It can slow down root growth by retarding cell division.
• Necrosis: In severe cases, excess cobalt can cause leaf necrosis (tissue death).
Effects on animals
• Cardiovascular System: High cobalt intake can lead to heart muscle disease and an increase in red blood cells.
• Gastrointestinal System: Acute exposure can cause vomiting, nausea, and diarrhea.
• Endocrine System: Excess cobalt can enlarge the thyroid gland and reduce its activity. It can also increase blood
sugar levels.
• Nervous System: High cobalt levels can affect the central and peripheral nervous systems, and it has been
observed to decrease neural transmission.
• Metabolic and Immune Effects: It can interfere with steroid metabolism, reduce immune response, and lead to
other systemic changes in organs like the liver, kidneys, and brain.
Zinc
An adult has about 1.5-3.0 g Zn with the largest amounts being in liver and bone. There is evidence that Zn
concentrations in blood and several tissues vary considerably in response to many stimuli. Zinc appears to be critical
in many functions. Human Zn deficiency in an inherited form in infants is termed acrodermatitis enteropathica and is
characterized by behavioral disturbances, diarrhoea, hair loss and severe peri-orificial skin rash, all of which respond
with remarkable promptness to Zn administration. Similar syndromes have now been reported many times with
penicillamine treatment of other disorders, presumably due to chelation of Zn, as well as during total parenteral
nutrition when Zn was not added to the nutritional solutions for even as short a time as two weeks.
Key roles of zinc in biological systems
• Enzymatic and structural roles: Zinc is a cofactor for hundreds of enzymes, including carbonic anhydrase
(involved in carbon dioxide regulation) and carboxypeptidase (involved in protein digestion). It also stabilizes the
structure of many proteins, such as zinc-finger proteins.
• Immune function: Zinc is necessary for the proper development and function of immune cells, such as
neutrophils, natural killer cells, and T and B lymphocytes. A deficiency can weaken both innate and acquired
immunity.
• DNA and RNA synthesis and repair: Zinc is required for the function of DNA and RNA polymerases, which
Metal ions present in biological systems, classification of elements according to their action in biological system.
Biological systems contain a wide range of metal ions, including ---
(1) Major ones like sodium (𝑁𝑎+), potassium (𝐾+), calcium (𝐶𝑎2+), magnesium (𝑀𝑔2+), iron (𝐹𝑒), copper (𝐶𝑢), and zinc
(𝑍𝑛),
(2) Trace elements like manganese (𝑀𝑛), cobalt (𝐶𝑜), and molybdenum (𝑀𝑜).
These ions are crucial for numerous functions, such as acting as cofactors in enzymes, transporting molecules, storing
energy, and playing roles in signal transduction.
Major metal ions:
● Sodium and Potassium: Essential for nerve impulse transmission by creating electrochemical gradients across
cell membranes.
● Calcium: Involved in signal transduction, blood clotting, and muscle contraction.
● Magnesium: A cofactor in many enzymes, such as those involved in energy production, and is a component of
chlorophyll.
● Iron: A key component of hemoglobin and myoglobin for oxygen transport, and a cofactor in many enzymes.
● Copper and Zinc: Found in various enzymes and proteins, playing roles in oxidation-reduction reactions and
protein structure.
Other important metal ions:
● Manganese: Involved in photosynthesis and is a component of enzymes like superoxide dismutase.
● Cobalt: Essential for vitamin 𝐵12
● Molybdenum: A cofactor in enzymes those are crucial for nitrogen fixation and other metabolic processes.
● Vanadium: Plays a role in some marine organisms.
Classification of elements according to their action in the biological system
Elements
Essential Trace Non-essential Toxic
O, C, H, N, P I, Fe, Cu, Zn, Mn, Al, Sr, Ba, Sn etc Cd, Pb, Hg
etc
Na, K, Mg, Cl, Co, Mo etc,
Ca, S etc.
I. Essential elements are absolutely essential or necessary for life processes. Trace elements are also
necessary for life processes.
II. Non-essential elements are not essential. If they are absent other elements may serve the same function.
III. Toxic elements disturb the natural functions of the biological system.
METAL IONS IN THE BIOLOGICAL SYSTEM
Metal ions their excess and deficiency
, Concentration of metal ions in human being’s system is controlled within very fine limits. This control is
generally exercised by certain biological complexing agents. The deficiency or excess of metal ions causes
disorder, which leads to various diseases.
Calcium
Calcium is a critical element in all animals and man. The primary dietary source of Ca is milk (65-76%), with
smaller amounts derived from meat, fish and eggs (5-10%). Dietary deficiency of Ca is not a common problem in
nations with high dairy product and protein intake, particularly since normal individuals can regulate intestinal
absorption and renal conservation mechanism with great precision. Hence, human health problems related to
geochemical distribution of Ca, its entry into the human food chain and its bio- availability are relatively uncommon.
Effect of Excess of Ca:
In case of excess of Ca, it comes in to the blood as Ca is rejected by cell and its salts are not soluble. So excess of
Calcium in blood leads to the (i) formation of stones, (ii) hardening of arteries, and (iii)cataracts in the eye.
Role of Ca:
Role in Animal:
• Skeletal structure: Around 99% of the body's calcium is stored in bones and teeth as hydroxyapatite, providing
structural strength and a reserve for other bodily functions.
• Muscle function: Calcium is essential for muscle contraction and relaxation, including the regular beating of the
heart.
• Nerve function: It is crucial for nerve impulse transmission and plays a role in the development and remodeling
of neural cells.
• Blood clotting: Calcium ions are a necessary component in the coagulation cascade, which helps in the efficient
healing of wounds.
• Cell signalling: Calcium acts as a universal second messenger, triggering and regulating a vast array of cellular
activities, from fertilization to cell death.
Roles in plants
• Cell wall stability: Calcium helps to stabilize the cell walls of plants, which is important for their overall growth
and structural integrity.
• Stress response: It plays a role in plant signaling and responses to environmental stresses like drought and salt
stress.
Magnesium
Role : Magnesium, an abundant element in the earth’s crust, is vital to both plant and animal life. Chlorophyll
pigment in plants is a Mg-porphyrin complex. All enzymatic reaction in animals and men that are catalyzed by ATP
require Mg as a cofactor. Oxidative phosphorylation, DNA transcription, RNA function, protein synthesis and critical
cell membrane functions are all dependent upon optimal Mg concentrations. Dietary sources high in Mg include nuts,
sea foods, legumes and vegetables; meat is intermediate in Mg content.
Effect of Excess of Mg:
1. Cardiovascular effects:
• Low blood pressure (hypotension)
• Slowed heart rate (bradycardia)
• Heart block and other arrhythmias
• Cardiac arrest
2. Neurological and neuromuscular effects:
• Lethargy and confusion
• Muscle weakness or paralysis
• Decreased or absent deep tendon reflexes
• Respiratory depression or paralysis
Potassium
An adult human has approximately 140 g K of which >90% is both intracellular and exchangeable (K is the
predominant cation in intracellular water) since muscle contains most of the body’s intracellular water, it also contains
most of the K. Since K is found in most animal and vegetable foods, dietary deficiency is exceedingly rare except
under unusual conditions (such as diets very high in refined sugars, alcoholic individuals deriving most of their
calories from low-K alcoholic beverages in the states of starvation etc.).
Key biological roles of potassium
• Fluid and electrolyte balance: As the primary intracellular ion, potassium maintains the body's fluid balance and
, is a key part of the electrolyte balance with sodium.
• Nerve function: It is essential for the transmission of nerve signals and the maintenance of the electrochemical
gradients necessary for nerve cell function.
• Muscle contraction: Potassium helps stimulate calcium ions to move across the cell membrane, which triggers
muscle cells to contract. It is vital for both skeletal and smooth muscle contractions, including the heart muscle.
• Cellular processes: It is involved in processes like the oxidation of glucose to produce energy (ATP) and activates
many enzymes.
• Heart health: Potassium helps ensure the heart muscle beats regularly. Low potassium levels can lead to abnormal
and irregular heart rhythms.
• Nutrient transport: It helps move nutrients into cells and waste products out of cells.
• Blood pressure regulation: A diet rich in potassium can help offset some of the harmful effects of sodium and
lower blood pressure.
Effect of Excess of K:
In plants:
• Nutrient imbalance: Excess potassium (K) competes with other positively charged nutrients (cations)
such as magnesium (Mg) and calcium (Ca) for absorption by the plant's roots.
• Induced deficiencies: This competition can lead to a deficiency in these other essential nutrients, even if
they are present in the soil, most notably causing magnesium deficiency.
• Leaf Yellowing: A visible sign of induced magnesium deficiency is interveinal chlorosis (yellowing
between the veins) on older leaves.
• Growth impact: These imbalances can limit overall plant growth, stunt development, and reduce fruit
or yield, as seen in both corn and soybean crops.
In animals
• Cardiac issues: In animals, the most serious effect of excess potassium is its impact on the heart.
• Arrhythmias: High potassium can cause cardiac arrhythmias, or irregular heartbeats, notes Wag!.
• Severity: While a veterinarian would likely notice the irregular heartbeat, severe cases can lead to more
obvious symptoms like coughing and fainting.
Sodium
Sodium is the predominant extracellular cation in animals and man. An adult human has about 105 g Na, about
24% is located in bone and about 65% in extracellular water. Sodium ion equilibrium is maintained primarily by the
kidney, the key organ in water and electrolyte balance. Sodium chloride (salt) is the predominant dietary source.
Excess sodium harms plants by causing osmotic stress, making water absorption difficult, and creating ion toxicity
that inhibits photosynthesis and nutrient uptake, leading to stunted growth and wilting. In animals, excess sodium can
lead to dehydration, electrolyte imbalance, and salt toxicity, which can be life-threatening.
Key roles of sodium in the body:
• Nerve impulse transmission: Sodium ions are crucial for transmitting nerve signals throughout the body.
• Fluid and electrolyte balance: Sodium helps maintain the body's overall fluid balance and electrolyte levels, which
is vital for many bodily functions.
• Nutrient transport: It plays a significant role in the transport of sugars and amino acids into cells.
• Heart function: Sodium is necessary for the proper functioning of the heart muscle.
• Muscle contraction: It works with other electrolytes to regulate muscle contraction and relaxation.
• Water regulation: It helps regulate the flow of water across cell membranes.
Effect of Excess sodium:
In plants
• Osmotic stress: High salt concentrations in the soil create a low osmotic potential, making it difficult for plants to
absorb water from the soil.
• Ion toxicity: Excessive sodium ions and chloride ions can be absorbed by the plant, damaging tissues and
interfering with cellular functions.
• Nutrient imbalance: Sodium can outcompete essential nutrients like potassium magnesium, and calcium for
uptake, leading to nutrient deficiencies.
• Photosynthesis reduction: The combination of stress and nutrient deficiency leads to lower rates of
photosynthesis and can impair energy and lipid metabolism.
• Growth inhibition: Excessive sodium reduces leaf expansion, and overall growth, which can lead to plant death.
In animals
• Dehydration: High sodium intake can cause animals to become dehydrated because their bodies are unable to
properly regulate water balance.
, • Electrolyte imbalance: The natural balance of electrolytes in the body is disrupted, affecting normal body
functions.
• Salt toxicosis: In severe cases, the body can no longer cope with the high salt concentration, leading to a
condition known as salt poisoning, which can be fatal.
• Nervous system effects: Sodium is crucial for nerve function, but too much can lead to neurological problems
Cobalt:
Cobalt is an essential element for humans, but its pathway through the food chain to human being remains elusive.
Only a little over 1 mg Co is present in an adult human. In man dietary Co deficiency is only likely among strict
vegetarians or when the intrinsic factor from the stomach that facilitates decreased as in pernicious anaemia.
Key roles of cobalt:
• Vitamin B12 (Cobalamin): Cobalt is the central atom in vitamin B12, a coenzyme necessary for several
enzymes. The active forms, methylcobalamin and adenosylcobalamin, are essential for metabolic processes.
• DNA and protein synthesis: Vitamin B12, and therefore cobalt, is required for the synthesis of DNA and the
production of amino acids and proteins.
• Red blood cell production: Cobalt is essential for the production of red blood cells and can help prevent anemia.
• Nervous system health: It plays a crucial role in the functioning of the nervous system and is involved in
preventing demyelination, which can lead to conditions like multiple sclerosis.
• Metabolism: Cobalt aids in the metabolism of fats and carbohydrates and the conversion of folate into its active
form.
• Plant growth: Cobalt is necessary for the nitrogen-fixing process in leguminous plants, as it is a component of
vitamin B12 required by the symbiotic microbes.
Effect of Excess cobalt:
Effects on plants
• Growth and Development: High levels of cobalt can inhibit growth, reduce biomass, and lead to leaf loss.
• Nutrient Uptake: It can hinder the plant's ability to absorb essential nutrients like iron, leading to iron deficiency
(chlorosis).
• Photosynthesis: Cobalt stress can reduce photosynthetic efficiency and cause ultrastructural damage to
chloroplasts.
• Root Inhibition: It can slow down root growth by retarding cell division.
• Necrosis: In severe cases, excess cobalt can cause leaf necrosis (tissue death).
Effects on animals
• Cardiovascular System: High cobalt intake can lead to heart muscle disease and an increase in red blood cells.
• Gastrointestinal System: Acute exposure can cause vomiting, nausea, and diarrhea.
• Endocrine System: Excess cobalt can enlarge the thyroid gland and reduce its activity. It can also increase blood
sugar levels.
• Nervous System: High cobalt levels can affect the central and peripheral nervous systems, and it has been
observed to decrease neural transmission.
• Metabolic and Immune Effects: It can interfere with steroid metabolism, reduce immune response, and lead to
other systemic changes in organs like the liver, kidneys, and brain.
Zinc
An adult has about 1.5-3.0 g Zn with the largest amounts being in liver and bone. There is evidence that Zn
concentrations in blood and several tissues vary considerably in response to many stimuli. Zinc appears to be critical
in many functions. Human Zn deficiency in an inherited form in infants is termed acrodermatitis enteropathica and is
characterized by behavioral disturbances, diarrhoea, hair loss and severe peri-orificial skin rash, all of which respond
with remarkable promptness to Zn administration. Similar syndromes have now been reported many times with
penicillamine treatment of other disorders, presumably due to chelation of Zn, as well as during total parenteral
nutrition when Zn was not added to the nutritional solutions for even as short a time as two weeks.
Key roles of zinc in biological systems
• Enzymatic and structural roles: Zinc is a cofactor for hundreds of enzymes, including carbonic anhydrase
(involved in carbon dioxide regulation) and carboxypeptidase (involved in protein digestion). It also stabilizes the
structure of many proteins, such as zinc-finger proteins.
• Immune function: Zinc is necessary for the proper development and function of immune cells, such as
neutrophils, natural killer cells, and T and B lymphocytes. A deficiency can weaken both innate and acquired
immunity.
• DNA and RNA synthesis and repair: Zinc is required for the function of DNA and RNA polymerases, which
