Chemistry of Signalling Metals

Question 1

where are metals found in the periodic table?

Answer 1

alkali metals: group 1
alkaline earth metals: Group 2
transition metals: d-block

Question 2

what processes are metal ions essential for?

Answer 2

• transcription
• translation
• signalling
• transport
• catalysis

Question 3

what are sodium, potassium and calcium essential for?

Answer 3

neuronal signalling with Na and K helping with transfer along the neurone and Ca helps with passing signals from one neurone to the other

Question 4

how do Na+ and K+ help to transmit signals along a neurone (action potential)?

Answer 4

• at resting potential (-70mV) there is a great positive charge outside the cell than inside due to high Na+ conc outside. Inside there are K+ and negatively charged proteins.
• sodium channels are closed when the neurone is at rest and becomes opens when activated to bring in Na+ ions (depolarisation)
• this increases the potential of the cell to -40mV.
• more Na+ channels open further down the neurone passing the signal all the way down the axon.
• Na+ channels then close and more K+ channels open to move K+ out of the cell to make the cell more negatively charged. (repolarisation)
• hyperpolarisation occurs when the cell lets out too many K+ ions so potential falls below resting potential.
• K+ ion channels and Na+/K+ channels correct this to return the membrane to resting potential. Na+/K+ channels bring 3Na+ out of and take 2K+ into the cell.

Question 5

how doe calcium channels help to transmit signals between neurones?

Answer 5

• action potential depolarises axon terminal
• depolarisation opens voltage-gated Ca2+ channels so Ca2+ enters the cell
• this triggers exocytosis of synaptic vesicles (i.e. they fuse with the cell membrane.
• neurotransmitter diffuses out the vesicles into the synaptic cleft then binds to the receptors on the postsynaptic cell
• this binding causes a response in the postsynaptic cell

Question 6

what is the role of Ca2+ in meiosis?

Answer 6

-it activates the ovum after sperm fertilisation

Question 7

what is the role of Ca2+ in mitosis?

Answer 7

• high Ca2+ conc during metaphase-anaphase transition

- suggests calcium has a role in signalling anaphase

Question 8

what is the main role of magnesium?

Answer 8

acts a co-factor aiding the reactivity of others

Question 9

what can result from inadequate Mg intake?

Answer 9

muscle spasms, cardiovascular disease, osteoporosis, diabetes, high blood pressure, anxiety disorders, migraines, cerebral infarction

Question 10

what is the role of Mg in DNA and RNA?

Answer 10

to stabilise the DNA or RNA in the cellular environment by neutralising the negatively charged phosphate groups

Question 11

what role does Mg have on insulin?

Answer 11

-it helps in the tyrosine-kinase activity, which promotes insulin activity.

Question 12

what is the role of manganese?

Answer 12

it is a cofactor and particularly important in the detoxification of superoxide free radicals in organisms that deal with elemental oxygen

Question 13

what can happen with high levels of manganese in the system

Answer 13

1. manganism-condition that leads to neurological damage and is sometimes irreversible
2. neurodegenerative disorders can arise from high manganese levels causing dopaminergic neuronal death and symptoms related to Parkinsons disease

Question 14

what does arginase do?

Answer 14

catalyses the 5th and final step in urea cycle

Question 15

What is superoxide dismutase (SOD) and what does it do?

Answer 15

an enzyme

-catalyse the dismutation (partitioning) of the superoxide (O2-) radical into oxygen or hydrogen peroxide

Question 16

how are superoxides produced?

Answer 16

as a bi-prouct of oxygen metabolism and causes cell damage

Question 17

hydrogen peroxide is damaging, how is it degraded in the body?

Answer 17

by enzymes e.g. catalase

Question 18

where are manganese SOD’s present?

Answer 18

in nearly all mitochondria