enzyme practical Flashcards

(12 cards)

1
Q

detailed method

A

-using a pen, draw an X on glass test tubes
-add10cm3 of milk powder solution to each test tube
-add 2cm3 of trypsin solution to 2cm3 of pH7 buffer in another set of test tubes
-stand all test tubes in water bath at 20 degrees for 10 mins
-add trypsin and buffer solution into milk powder solution test tube and mix thoroughly
-put tube back in water bath
-repeat using other test tubes
-time how long it takes for the milk to go clear by measuring time taken to see the X clearly
-record time for each three experiments, gather a mean
-repeat at different temperatures in 10 degree differences
-record data and draw bell curved graph

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2
Q

what are the independent variables

A

temp
pH
enzyme conc
enzyme volume

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3
Q

what are the dependent variables

A

rate of reaction
time taken for solution to turn clear

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4
Q

why are the test tubes left in water baths for 10 mins before the trypsin and milk are added together

A
  • to equilibrate temperatures for reaction to take place
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5
Q

why do you wear safety goggles and gloves

A
  • may have allergic reaction to enzymes
  • avoid contact w eyes and skin
  • also risk of burning yourself
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6
Q

why did the milk become clearer

A

the enzyme trypsin breaks down (hydrolyses) the milk protein into smaller peptides, reducing the opacity of the milk, allowing more light to pass through

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7
Q

explain use of buffer solution

A

to maintain constant pH

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8
Q

describe and explain what you did to make sure the temperatures of water baths were reliable

A

measure temp of water bath throughout or at the start and then the end of reacting period

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9
Q

why were three test tubes used per temperature investigation

A

enables calculation of a reliable mean
allows easy identification of anomalies

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10
Q

A student decided to improve this investigation with control experiments. At each temperature she set up a test tube containing a solution of milk powder and buffer. She did not add trypsin. What would these control experiment show?

A

Controls show that the casein digested was due to the action of enzyme / not due to temperature changes

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11
Q

It is difficult to decide when the milk solution goes clear. Suggest one better way of determining when the milk solution goes clear.

A

use a colorimeter, record time taken to reach a set value of absorbance

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12
Q

drawbacks of this investigation

A

-lots of room for human error as the idea of clear colour is very subjective, some people will view ‘clear’ differently
-water temperature might be difficult to maintain temperature
-hard to know if solutions have been shaken the exact same to the same extent

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