Effect of ions on living organisms (24 marks)
An ion is a charged atom or molecule. This is because it does not have an equal amount of protons and electrons, therefore giving the atom an overall charge. An example of an ion is , this is sodium and the plus sign represents an overall positive charge. Ions are very important to living organisms as they are essential for life, they play an important role within the cell allowing mechanisms within the living organisms such as respiration, to take place. Ions play a big part in the nitrogen cycle. During the nitrogen cycle, plants take up nitrate ions from the soil by active transport through the root hair cells. This is then used to make proteins within the cell. Consumers then eat the plants and digest these proteins and then convert them into amino acids for growth, therefore the protein is passed along the food chain. Ions are also used in the nitrogen cycle during de-nitrification; where the nitrates are converted to nitrogen gas. Also, ions are present during nitrification where ammonium ions are oxidised to nitrites then nitrates by nitrifying bacteria. Therefore, without ions, the nitrogen cycle would not be able to occur. In addition, some living organisms would not be able to survive as they cannot get nitrogen direct from air therefore would not have proteins for growth and repair; showing the importance of ions and the effect they have on living organisms. Some of the more important ions are sodium, potassium and calcium. Sodium and potassium are important within the nervous impulse; without those living organisms would not be able to send an impulse across a nerve, therefore we would not be able to survive. This is because, for depolarisation to take place, firstly there must be a resting potential at -70mv, this is acquired by the sodium-potassium pump, which pumps 3 ions out of the ion in exchange for 2 ions into the axon. But the membrane is more permeable to potassium than sodium, therefore...
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