Enzymes

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What makes up the cell’s metabolism?
The different chemical reactions going on inside the cell at all time. E.g. - respiration, photosynthesis and protein synthesis
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Why do the chemical reactions in a cell need to be carefully controlled?
To get right amounts of substances and keep the organism working properly
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How can you make a reaction happen more quickly?
By raising the temperature
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What is an advantage of raising the temperature to speed up a chemical reaction?
It speeds up the useful reactions
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What is a disadvantage of raising the temperature to speed up a chemical reaction?
It speeds up the unwanted reactions
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Why is there a limit to how far you can raise the temperature inside a living creature?
Because its cells can start getting damaged
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What do enzymes act as?
Biological catalysts
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What is a catalyst?
A substance that speeds up a reaction, without being changed or used up in the reaction itself
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What do enzymes reduce?
The need for high temperatures
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Why do we have enzymes?
To speed up the useful chemical reactions in the body
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What does every different biological reaction have?
Its own enzyme especially for it
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What is each enzyme protein coded for by?
A different gene
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Why does each enzyme have an unique shape?
It needs to have a unique shape to do its jobs
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What do chemical reactions usually involve?
Things being split apart or joined together
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What is the substrate?
The molecule changed in the reaction
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What is the active site?
The part where it joins on to its substrate to catalyse the reaction
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Why do enzymes have a high specificity for their substrate?
Because they usually only work with one substrate
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What is needed for the enzyme to work?
The substrate has to fit into the active site
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What happens if the substrate’s shape doesn’t match the active site’s shape?
Then the reaction won’t be catalysed
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Why is the reaction between the substrate and active site called the ‘lock and key hypothesis’?
Because the substrate fits into the enzyme just like a key fits into a lock
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Enzymes are described as having a ‘high specificity’ for their substrate. What is meant by this?
Enzymes have an active site, which the substrate has to fit into in order for the reaction to be catalysed. This means that enzymes usually only work with one substrate so they are very specific
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What does changing the temperature do to the enzyme-controlled reaction?
Changes the rate of an enzyme-controlled reaction
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What happens when the temperature is increased in an enzyme-controlled reaction?
The enzymes and the substrate move about more, so they’re more likely to meet up and react
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What happens to the bonds holding the enzymes together if the temperature gets too hot?
The bonds holding the enzymes together break
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When the bonds holding the enzyme together break, what happens to the enzyme?
It becomes denatured—it loses its shape and the substrate doesn’t fit the active site any more.
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What happens if the substrate doesn’t fit into the active site anymore?
The enzyme can’t catalyse the reaction and the reaction stops
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What does it mean when the enzyme is denatured irreversibly?
It won’t go back to its normal shape if things cool down again
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What does each enzyme have to make the reaction go its fastest?
Its own optimum temperature
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What is the optimum temperature?
Before it gets too hot and starts to denature
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What is the optimum temperature for the most important human enzymes?
37°C - our body temperature
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What happens if the pH is too high or too low in an enzyme reaction?
It interferes with the bonds holding the enzyme together
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What does the pH do to the enzyme if it’s too high or too low?
It changes the shape of the active site and can irreversibly denature the enzymes
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What is the often optimum pH that enzymes best work at?
Neutral pH 7
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Why does increasing the concentration of the enzyme increase the rate of reaction?
Because the more enzyme molecules there are in a solution, the more likely a substrate molecule will meet up with one and join with it
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What happens if the substrate is limited?
Then there are more than enough enzyme molecules to deal with all the available substrate, so adding more enzymes has no further effect
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What happens when the substrate concentration is high?
The reaction is faster - it is more likely the enzyme will meet up and react with a substance molecule
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What happens when the substrate concentration becomes too high?
There are too many substrate molecules that the enzymes have about as much as they can cope with (all the active sites are full), adding more makes no difference
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How can you investigate the effect of pH in an enzyme reaction?
Add a buffer solution with a different pH level to a series of different tubes containing the enzyme-substrate mixture
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What is the calculation for the mean rate of reaction?
Mean rate of reaction = The mean volume of oxygen produced (cm3) ÷ The time taken (seconds)
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If starch is present, what colour does the iodine solution go?
From browny-orange to blue-black
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An enzyme-controlled reaction was carried at 25°C. After 60 seconds, 33cm3 of product had been released. Calculate the rate of reaction in cm3/second.
33 ÷ 60 = 0.55cm3/second
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Other cards in this set

Card 2

Front

Why do the chemical reactions in a cell need to be carefully controlled?

Back

To get right amounts of substances and keep the organism working properly

Card 3

Front

How can you make a reaction happen more quickly?

Back

Preview of the front of card 3

Card 4

Front

What is an advantage of raising the temperature to speed up a chemical reaction?

Back

Preview of the front of card 4

Card 5

Front

What is a disadvantage of raising the temperature to speed up a chemical reaction?

Back

Preview of the front of card 5
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