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How does the kidney filter out different molecules?

In the blood flowing through the kidneys, you find lots of different substances, like glucose and amino acids (which the body wants to keep and use) and urea (which the body wants to get rid of). The first i...
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Answered by Isobel E. • Biology tutor
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Explain how DNA replicates inside a cell

DNA is made up of 4 bases (Adenine, Thymine, Guanine, Cytosine) Adenine, guanine = purine 'Pure AGony' Thymine and cytosine = pyramidines Adenine pairs with thymine (2 Hydrogen bonds - '2 people know where i...
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Answered by Claire D. • Biology tutor
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Describe the similarities and differences between simple diffusion, facilitated diffusion and active transport.

Simple diffusion, facilitated diffusion and active transport are three methods to transport various molecules across a membrane. Whilst similar in the overall effect, there are some major differences between...
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Answered by James G. • Biology tutor
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Describe how the fluidity of the membrane and how this allows transport across it.

The fluidity of membranes allows it to invaginate and form vesicles. This is important for the process of endocytosis by which the cell is able to uptake materials from the extracellular environment. Vesicle...
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Answered by Naomi H. • Biology tutor
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A neuron transmits an electrical impulse across a synapse in order to pass this impulse to the next neuron. Outline this process.

This is an example of a common process that must be known: Impulse reaches the synaptic bulb, causing calcium channels to open and calcium to enter. This causes synaptic vesicles to move towards the pre-syna...
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Answered by Matthew M. • Biology tutor
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