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How is the the small intestine adapted for absorption?

The Ileum is long (up to 7m!) and has a very high surface area due to the presence of many villi and microvilli . A single villus is made up of many cells, each with lots of microvilli, and have many blood v...
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Answered by James P. • Biology tutor
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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 transmiss...
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Answered by Rafee A. • Biology tutor
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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 pres...
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Answered by Anshul A. • Biology tutor
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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 throughout ...
AM
Answered by Anika M. • Biology tutor
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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 requires oxygen to be broken down an...
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Answered by Tom M. • Biology tutor
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