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Biology
A Level

Why is the oxygen saturation curve of haemoglobin sigmoidal?

The saturation curve of haemoglobin shows positive cooperativity. Initially, the porphyrin ring of the haem prosthetic group in haemoglobin is dome-shaped. When one molecule of oxygen binds one of the fou...

YM
Answered by Yunzila M. Biology tutor
2352 Views

What is the benefit of myelination of an axon?

Myelination of an axon makes propagation of action potentials along it much faster. In unmyelinated axons, the action potential is constantly regenerated by active propagation, with the depolarisation cau...

YM
Answered by Yunzila M. Biology tutor
2667 Views

Explain three ways in which the structure of the xylem vessels makes them well-adapted to their function.

The end walls are removed from each end, forming an uninterrupted tube, so water can pass through easily.Their walls are thickened with a woody substance called lignin, w...

HW
Answered by Hannah W. Biology tutor
53080 Views

Describe the generation of action potentials in neurons.

When the neuron is stimulated, it causes rapid depolarisation of the cell surface membrane. This will not generate an action potential unless it is large enough to exceed the threshold potential...

HR
Answered by Howard R. Biology tutor
4908 Views

Why is water being a solvent important?

dilute harmful substancestransport in bloodstream and plantsfor metabolic reactions to occurseparation of substancesabsorption of ions etc.

SA
2351 Views

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