Top answers

Briefly describe the mechanism of muscle contraction.

In muscle, myosin protein has 'heads' that act as cross-bridges as they bind to actin, another protein. When ATP binds to myosin, its head detaches from actin, swings forward and rebinds. Rebinding releases ...
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Answered by Hester G. • Biology tutor
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Describe some of the means by which a plant might defend itself, bearing in mind that it is 'sessile' (it cannot move around)?

The plant could have structural defence mechanisms such as 'thorns' or 'spines' which could cause damage to the mouth of herbivores so the plant is not eaten. It could also have 'stings' which are little hai...
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Answered by Hester G. • Biology tutor
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I know all the theory, but I can never score well with the essay questions in paper 2. Why?

As you've probably noticed, the mark scheme is incredibly specific about the terminology that you use. You could describe the process of, say, endocytosis, to great accuracy, but if you don't use the exact k...
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Answered by Amy W. • Biology tutor
5143 Views

What's the difference between diffusion and osmosis?

These 2 processes can be easily confused because they are both based on the idea of molecules moving from an area of HIGH concentration to LOW concentration. Diffusion= movement of ANY molecule. From an area...
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Answered by Francesca H. • Biology tutor
7646 Views

What are Enzymes ?

Enzyme are biological catalyst that speeds up the rate of the reaction without being used up. Enzymes speeds up the rate of chemical reaction by providing an alternative route to the reaction which lowering ...
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Answered by Mahima L. • Biology tutor
3396 Views