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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 ca...
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Answered by Emiliya T. • Biology tutor
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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 th...
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Answered by Tamarind R. • Biology tutor
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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 causes...
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Answered by James M. • Biology tutor
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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 is...
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Answered by Martyna S. • Biology tutor
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What are the four chambers of the heart and what do they do?

The four chambers are called the right atrium, the left atrium, the right ventricle and the left ventricle. Deoxygenated blood enters the right atrium and is pumped into the right ventricle. The blood is the...
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Answered by Hannah M. • Biology tutor
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