Biological significance of various elements in  the Periodic Table

12) Al - T.E. implicated in Alzheimer's disease

13) Si - T.E. siliceous exoskeleton of diatoms (marine phytoplankton)
-  forms the sharp edges of grasses and sedges

14) P - limiting nutrient in most environments ATP, ADP, GTP, AMP,
nucleic acids , DNA,  teeth, bones

15) S - hydrogen sulphide was an early source of metabolic fuel
- important element in formation of several amino acids (disulphide bonds)
- primary source in formation of acid rain

16) Cl - important electrolyte

17) K important neuron (excitable tissue) electrolyte K + ion (bananas)
Voltage sensitive K⁺ gate

18) Ca - essential essential for muscle contraction, bone formation
- important electrolyte (need Vitamin D to absorb Ca) and neurotransmitter release at synapse

19) Cr, Mn T.E.

20) Fe - Fe++ sits in the centre of the porphyrin ring of hemoglobin and myoglobin
- iron deficiency leads to symptoms of anemia in animals and foliar and stem weakness in plants

21) Co - T.E. - produced in Canadian CANDU reactors
- CANDU reactors produce the world supply of CO 60 and powerful radioactive isotope used in cancer therapy
- half life (T1/2) 5.2Y    Gamma rays @1.172MeV
- cells in mitosis expose DNA and more vulnerable to ionizing radiation
- thus actively dividing cells (high mitotic index) are killed at higher rate than surrounding cells
- skin, G.I. tract epithelia, hair follicles, bone marrow are thus unfortunately affected as well

22) Ni, Cu, Zn, = T.E.  zinc often used in skin lotions to cure rashes
23) As = cyanotic

24) Se, Br, =  T.E.
25) Kr - radioactive form must not be brought to class