Top answers

Biology
A Level

If the concentration of testosterone in a man’s blood starts to rise above normal, this system leads to a reduction in testosterone. How does this occur?

Students are aware of the Hyothalamus-pituitary axis (HPA axis) in the female, but are not as aware about the role of the HPA axis in the male reproductive system. Here,we should start off by explaining t...

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Answered by Thahesh T. Biology tutor
3838 Views

How is the process by which plants turn towards a light source called and what is the role of auxin (IAA) in it?

The process is called phototropism (‘photo’-light, ‘tropism’ – ‘tendency of an animal or plant to turn or move in response to a stimulus’). IAA (Indole Acetic Acid) is a plant hormone belonging to a class...

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Answered by Emiliya T. Biology tutor
7898 Views

Name a substance that can be transported across a membrane by simple diffusion and explain why it is able to be transported by this method.

Oxygen is an example of a molecule that is able to move across a membrane via simple diffusion. It is able to do so as it is a non-polar, uncharged molecule. Thus, it is a lipophillic molecule which means...

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Answered by Tamarind R. Biology tutor
2441 Views

Describe the electrical conduction system of the heart and how it initiates the heart beat

The sinoatrial node (SAN) is the pacemaker of the heart and initiates a wave of excitation (impulse) at a regular interval. This wave of excitation sweeps across the walls of the atria and in doing so cau...

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Answered by James M. Biology tutor
10515 Views

Why is the model of the structure of biological membranes described as ‘fluid mosaic’?

The biological membrane is a complex, heterogenous structure, built by two lipid layers with proteins and molecules immersed and in it. Its properties were developed due to the fact that its main function...

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Answered by Martyna S. Biology tutor
3756 Views

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