Inorganic ions in
animals and
plants are
ions necessary for vital
cellular activity.[1] In body tissues, ions are also known as
electrolytes, essential for the electrical activity needed to support muscle contractions and neuron activation. They contribute to
osmotic pressure of
body fluids as well as performing a number of other important functions. Below is a list of some of the most important ions for living things as well as examples of their functions:
Ca2+ – calcium ions are a component of
bones and
teeth. They also function as biological messengers, as do most of the ions listed below. (See
Hypocalcaemia.)
Zn2+ - zinc ions are found in very small concentrations in the body, and their main purpose is that of an antioxidant; the zinc ions act as antioxidants both generally and for liver specific
pro-oxidants.[2] Zinc ions can also act as an antioxidant-like stabilizer for some macro-molecules which bind zinc ions with high affinity, especially in
cysteine-rich binding sites.[2] These binding sites use these zinc ions as a stabilizer to protein folds, making these protein motifs more rigid in structure. These structures include
zinc fingers, and have several different conformations.[2]
K+ – potassium ions' main function in animals is osmotic balance, particularly in the
kidneys. (See
Hypokalemia.)
Na+ – sodium ions have a similar role to potassium ions. (See
Sodium deficiency.)
Mn2+- manganese ions are seen being used as stabilizer for varying protein configurations. However, manganese ion overexposure is linked to several
neurodegenerative diseases such as
Parkinson's disease.[3]
Cl− – inability to transport chloride ions in humans manifests itself as
cystic fibrosis (CF)
CO2− 3 – the shells of sea creatures are
calcium carbonate. In blood approximately 85% of
carbon dioxide, is converted into aqueous carbonate ions (an
acidicsolution), allowing a greater rate of transportation.
Co2+- cobalt ions are present in the human body in amounts from 1 to 2 mg.[4] Cobalt is observed in the heart, liver, kidney, and spleen, and considerably smaller quantities in the pancreas, brain, and serum.[4][5] Cobalt is a necessary component of
vitamin B12 and a fundamental coenzyme of cell
mitosis.[5] Cobalt is crucial for amino acid formation and some proteins to create
myelin sheath in nerve cells.[6][3] Cobalt also plays a role in creating
neurotransmitters, which are vital for proper function within the organism.[3]
Fe2+/Fe3+ – as found in
haemoglobin, the main oxygen carrying molecule has a central iron ion.
NO− 3 – source of nitrogen in plants for the synthesis of proteins.
Biological functions of inorganic ions
Ion channels
K+ channels
Potassium ion channels play a key role in maintaining the membrane's electric potential. These ion channels are present in many various biological systems. They frequently play a role in regulation of cellular level processes, many of these processes including muscle relaxation, hypertension, insulin secretion etc.[7] Some examples of potassium ion channels within biological systems include
KATP channels,
BK channels, and
ether-a-go-go potassium channels[7]
Na+ channels
Sodium ion channels provide an integral service through the body, as they transmit depolarizing impulses at the cellular and intracellular level. This allows sodium ions to coordinate much more intensive processes such as movement and cognition.[8] Sodium ion channels consist of various subunits, however, only the principle subunit is required for function.[8] These sodium ion channels consist of four internally homologous domains, each of which containing six transmembrane segments and resembling a single subunit of a
voltage-dependent potassium ion channel.[8] The four domains fold together, forming a central pore.[8] That central pore of the sodium ions dictates the selectivity of the channel: both
ionic radius and ionic charge are key in channel selectivity.[8]
Cl− channels
Chloride ion channels vary from many other ion channels due to being controlled by the anionic chloride ions. Chloride ion channels are pore-forming membrane proteins that allow the
passive transport of chloride ions across biological membranes.[9] Chloride ion channels involve both
voltage-gated and
ligand-gated mechanisms to transport the ions across cellular membranes.[9] Chloride ion channels have been found to play crucial roles in the development of human diseases, for example, mutations in the genes encoding chloride ion channels lead to a variety of deleterious diseases in muscle, kidney, bone, and brain, including
cystic fibrosis,
osteoporosis, and
epilepsy, and similarly their activation is supposed to be responsible for the progression of
glioma in the brain and the growth of malaria-parasite in the red blood cells.[9] Currently, chloride ion channels are not completely understood, and more research is necessary.
^
abcGupta, Satya P.; Kaur, Preet K. (2011), Gupta, Satya Prakash (ed.), "Chloride Ion Channels: Structure, Functions, and Blockers", Ion Channels and Their Inhibitors, Springer Berlin Heidelberg, pp. 309–339,
doi:
10.1007/978-3-642-19922-6_11,
ISBN9783642199226