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Saltatory conduction refers to the passage of an action potential along a myelinated neurone. Myelin is a lipid that forms a fatty sheath around the neurone axon and it is an electrical insulator. This means...

Fertilisers are generally high in nitrogen, to replenish the nitrogen in the soil assimilated by the crop plants. When this is drained into lakes in run-off, it can cause dramatic consequences. Nitrogen avai...

Cholera is single-celled organism that produces a toxin. The toxin attaches to the ion receptors in the small intestine which causes it to secrete chloride ions into the lumen. This then causes water to move...

DNA is used to code proteins. This requires two steps: transcription and translation.Transcription is the conversion of double stranded DNA into a single stranded mRNA molecule. DNA nucleotides bind to their...

For many reasons cell division can become unregulated. This leads to the formation of a mass of cells called a tumour which cannot perform their normal function – they are said to be undifferentiated. In som...