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Knowing when to use the preterite or imperfect tense when expressing a past action is one of the trickiest aspects of spanish grammar and can cause confusion for any level of spanish speaker. I always lik...

Tips: When a keyword is mentioned in the question, it is advised to start your answer by defining that keyword or concept (you would usually get a few marks for this) . In this case, star...

An impulse travels along the pre-synaptic neurone, and when it reaches the axon ending it stimulates calcium channles to open on the pre-synaptic membrane. This allows calcium ions to rush into the neuron...

The two main past tenses in German are the simple past and the present perfect. The simple past uses just one word, for example 'ich ging', while the present perfect uses two words, for example 'ich bin g...

Enzymes are proteins. They are biological catalysts, meaning they increase the rate of reaction without being used up or changed. Different enzymes have different optimum temperatures and pHs, depending o...