The Formation of Urea in the Liver (4.2.1)

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How much protein do we need a day?
40-60g.
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Why can't amino acids be stored?
Because their amino groups make them toxic.
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What happens in deamination?
Amino acid and oxygen gives keto acid and ammonia.
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What happens in the ornothine cycle?
The toxic ammonia combines with oxygen to produce urea which is less soluble and less toxic. ATP is needed for this cycle.
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Where does the urea go?
It's passed into the bloodstream and then the kidneys where it's filtered and enters the urine. It's then stored in the bladder until it's released.
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Give examples of substances that the liver can detoxify.
Alcohol. Drugs. Hyrdogen peroxide- waste product from cellular reactions.
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What do liver cells do to hydrogen peroxide?
Use the enzyme catalase to convert it into water and oxygen.
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What is ethanol?
A small, lipid-soluble molecule- it can pass into cells easily. It is toxic.
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How is alcohol detoxified?
Enzyme ethanol dehydrogenase converts ethanol to ethanal & H is given off. The ethanal dehyrdogenase enzyme converts ethanol to ethanoate & H is given off. Co-enzyme A converts ethanoate into Acetyl-co-A. This can enter respiration to release energy.
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What happens to the hydrogen atoms given off in the detoxification of alcohol?
These can reduce NAD which is a substance found in liver cells
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How does reduced NAD cause problems?
NAD needed by liver to break down fatty acids for use in respiration. If too much alcohol is consumed, more NAD is reduced- isn't enough NAD to deal with fatty acids. Turned back to lipids & stored in liver cells. Liver gets enlarged- fatty liver.
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Other cards in this set

Card 2

Front

Why can't amino acids be stored?

Back

Because their amino groups make them toxic.

Card 3

Front

What happens in deamination?

Back

Preview of the front of card 3

Card 4

Front

What happens in the ornothine cycle?

Back

Preview of the front of card 4

Card 5

Front

Where does the urea go?

Back

Preview of the front of card 5
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