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Biology
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Tetrodotoxin (TTX) is a chemical found in pufferfish which binds to voltage-gated sodium channels causing inactivation via a conformational change. Poisoning can result in paralysis leading to death. How might this occur? (4 marks)

This question asks about nerve action potential generation. There are a couple of clues - these include 'voltage-gated sodium channels' and 'paralysis' which suggests the idea of failure of impulse transm...

Answered by Rafee A. Biology tutor
3812 Views

What are the main stages of the cardiac cycle?

Blood enters the atria. It cannot pass into the ventricles because the atrioventricular valves are closed. The heart is in diastole.The atria contract. The pressure in the atria becomes greater than the p...

Answered by Anshul A. Biology tutor
4267 Views

How are leaves adapted for gas exchange?

Leaves have a large surface area, which means more space to allow CO2 to enter. They are thin so there is less for gases to travel. Leaves contain Stomata; these are small holes found distributed througho...

Answered by Anika M. Biology tutor
36100 Views

Compare anaerobic respiration in a yeast cell with anaerobic respiration in a muscle cell.

Anaeobic respiration in yeast:
glucose -> carbon dioxide + ethanol

Anaerobic respiration in muscle cells:
glucose -> lactic acid

The lactic acid build up in muscles r...

Answered by Tom M. Biology tutor
25626 Views

Describe methods of solute transport across a cell membrane.

For non-polar small molecules simple diffusion down a concentration gradient through the phospholipid bilayer is possible as it is soluble in the hydrophobic fatty acid tails of the membrane. An example o...

Answered by Ayano F. Biology tutor
2595 Views

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