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The role of the sperm cell is to fertilise the egg.- It has a streamlined shape with a tail which enables it to swim towards the egg.- It has a head with a nucleus, which contains the genetic ma...
A DNA molecule is shaped in a double helix. It is composed of two sugar-phosphate backbones, conjoined by what we call 'bases'. These nitrogen bases: adenine, guanine, cytosine and thymine, which form the...
Red Blood Cells (erythrocytes) are approximately 0.01 mm, so only one can pass through the small capillary. The advantage of this is that there is a larger surface area exposed, more time available and sh...
Na+ ions are actively transported out of the epithelial cell into the blood by an Na+ pump. This requires ATP. This establishes a concentration gradient of Na+, with a high Na+ concentration in the ileum ...
The alveoli are arranged in clusters at the end of the bronchioles in the lungs. The lungs contain an extremely large surface area of alveoli (around 70m2) which acts to provide the maximum space for the ...
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