The functions of mineral ions in plants and animals
1) INTRO
a) Definition of mineral ions - inorganic ions (ie. they carry a charge and do not contain carbon or hydrogen)
b) examples include magnesium (Mg 2+), sodium (Na+), calcium (Ca2+) etc.
c) common knowledge that calcium is required for strong bones but there are many more important uses of mineral
ions within the body
d) obtained from diet
i) in plants selective uptake of minerals occurs through roots from soil
ii) plants pump +ve sodium ions out of roots to create a charge gradient which helps the uptake of other +ve
charged ions
iii) many plants rely on bacteria or fungi to help uptake of certain minerals
iv) minerals carried in solution in xylem
v) in humans absorbed in small intestine
2) MAIN BODY OF ESSAY
a) General functions
(1) phospholipid membranes require phosphate group
(2) nitrogen required to form amino acids (amine group)
(3) DNA - contains a phosphate group
(4) Copper and Iron used in the electron transport chain
b) Functions in animals
i) used to form a electrochemical gradient in:(1) neurones - resting potential (-70mV) is maintained by sodium and potassium (K+) pumps - more
sodium ions are pumped out of the neurone than potassium ions pumped in so a charge gradient is
formed resulting in a more negative charge inside the neurone
(2) neurones - action potential- at resting potential there is an electrochemical gradient between the inside
and outside of the neurone when an action potential occurs the membrane becomes permeable to
sodium ions and they rush in (along gradient) making it more +ve inside (+40mV)
(3) transmission of signals across synapses (Ca2+)- calcium ions diffuse into the synaptic terminal
causing the acetylcholine to be released into the synaptic cleft.
(4) muscle contraction (Ca 2+)- action potential stimulates muscle contraction because Ca2+ ions are
released from cisternae and the ions bind to actin filaments.
(5) kidneys- ions pumped out of tubule to create a charge gradient which causes -ve charged ions to follow
and forms a concentration gradient which causes water to diffuse out of tubule by osmosis
(6) respiration requires phosphate provided by ADP and NADPH2 for glycolysis and Kreb cycle
(phosphorylation of glucose etc.)
NB. Do NOT include hydrogen pumps or chemiosmotic theory, as hydrogen is not a mineral.
ii) form parts of specialised cells
(1) red blood cells- haemoglobin contains iron
(2) calcium required for strong bones, nails and teeth
(3) phosphate required in ADP and ATP
(4) iodine required to form thyroxine
c) Functions in plants- some mentioned for animals are also very important in plants eg respiration and amine group
in amino acids
i) required in specialised cells
(1) Chlorophyll contains magnesium
ii) phosphate group required for light independent reaction of photosynthesis (Calvin cycle)
iii) potassium- required in opening of stomata
iv) nitrates absorbed and reduced to ammonia beforebeing incorporated into, eg. protein.
3) CONCLUSION
a) mineral ions are very important in both plants and animals
b) supported by the fact that deficiency in any one mineral in plants or animals leads to disease
i) lack of calcium leads to rickets
ii) lack of iron leads to anaemia
iii) lack of magnesium in plants leads to less chlorophyll therefore leaves are white (chlorosis)