Top answers

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...
ET
Answered by Emiliya T. • Biology tutor
8882 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 th...
TR
Answered by Tamarind R. • Biology tutor
2990 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 causes...
JM
Answered by James M. • Biology tutor
11490 Views

How does the volume in the lungs change as we breathe?

As humans breathe in, the ribcage moves upwards and outwards. As this happens, the diaphragm flattens and moves down. This allows air to move into the lungs causing an increase in volume within the lungs. Th...
RW
Answered by Rebecca W. • Biology tutor
3483 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 is...
MS
Answered by Martyna S. • Biology tutor
4248 Views