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Where is DNA found in a human cell? What is a gene?

DNA is a long molecule found in the nucleus (or more specifically the nucleolus) of a human cell. When it is condensed and shortened it appears, under a microscope, as 23 pairs of chromosomes. A gene is a lo...
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Answered by Ryan M. • Biology tutor
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Describe the passive movement through diffusion and explain Fick's Law

Diffusion is the net passive movement of particles (atoms, ions or molecules) from a region in which they are in higher concentration to regions of lower concentration. It continues until the concentration o...
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Answered by Zuzana B. • Biology tutor
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How do muscle fibres contract?

Contraction occurs when an impulse from a motor neurone reaches the synapse at the junction with the muscle, the neuromuscular junction (NMJ). At the presynaptic membrane of the NMJ, depolarisation results i...
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Answered by Emily B. • Biology tutor
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Describe the different roles of aldosterone and cortisol in the body

Both aldosterone and cortisol are produced in the adrenal cortex of the adrenal gland (which are situated above the kidneys on either side of the body). Aldosterone is a mineralocorticoid and helps to contro...
AJ
Answered by Aiman J. • Biology tutor
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Describe the roll of kupffer cells in the liver

Kuppfer cells are a specialised type of macrophage. They travel within the sinusoids of the liver and breakdown and recycle old red blood cells. Red blood cells contain heamoglobin, and when haemoglobin is b...
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Answered by Aiman J. • Biology tutor
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