Introduction to Excretion (4.2.1)

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What is excretion?
The removal of unwanted products from metabolism, some of which are toxic.
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What are the main excretory products of the body?
Urea- made in liver from excess amino acids. CO2- from cell respiration.
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How is CO2 excreted?
Passed from respiring cells into bloodstream. Carried as HCO3- back to lungs. At lungs, it's converted back to CO2 and diffuses into alveoli for breathing out.
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How is urea excreted?
It's produced by deamination- breakdown of excess a.a in liver. Urea then passes into bloodstream and travels to kidneys. They then remove urea from blood during production of urine. This is temporarily stored in the bladder before being excreted.
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Why must CO2 be removed from the body?
Excess CO2 is toxic at a high level.
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Give one effect of too much CO2 in the body.
Too much carbon dioxide means excess H+ inside RBC, so more competition with O2 for the binding sites on haemoglobin. So less O2 can be carried in bloodstream.
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Give another effect of too much CO2 in the body.
Can cause respiratory acidosis. CO2 dissolves in plasma and combines with water to form carbonic acid. Can be caused by conditions such as asthma or emphysema.
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Why must urea be removed from the body?
The body can't store amino acids. They are transported to the liver where the toxic amino group is removed- deamination. This produces ammonia which is very soluble and toxic, so it's converted into urea, which can be safely transported and excreted.
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What can urea also be called?
Nitrogenous waste.
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Describe the reactions that lead to the production of urea.
Amino acids + oxygen --> keto acid + ammonia. Then ammonia + carbon dioxide --> urea + water.
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Card 2

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What are the main excretory products of the body?

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Urea- made in liver from excess amino acids. CO2- from cell respiration.

Card 3

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How is CO2 excreted?

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Card 4

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How is urea excreted?

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Card 5

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Why must CO2 be removed from the body?

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