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DNA is made up of nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C). N...

Blood that has been used up by the body (deoxygenated) enters the right side of the heart via a large vein known as the superior vena cava. It enters the right atrium from the top, which then contracts an...

Blood glucose level is controlled by two hormones, insulin and glucagon. These are produced by the pancreas. If the blood glucose (sugar) level is too high, then insulin is released. This causes glucose i...

The refractory period is a period of recovery after an action potential where the ion channels will not open and the membrane can't be excited or depolar...

The order of the amino acids (primary structure) in the two proteins may be different. This can result in ionic, hydrogen and disulphide bonds to form in different locations in each protein. Such differen...