Qualitative: Activity of Immobilised Enzymes
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Qualitative: Activity of Immobilised Enzymes I nvertase Breaks down sucrose into glucose and fructose Yeast cells make invertase Invertase is a reducing sugar Tests for biological molecules: Benedict's - blue to red/orange precipitate Biuret- blue to lilac

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Qualitative: Activity of Immobilised Enzymes I nvertase

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Qualitative activity of immobilised enzymes i nvertase

Qualitative: Activity of Immobilised Enzymes

Invertase

Breaks down sucrose into glucose and fructose

Yeast cells make invertase

Invertase is a reducing sugar

Tests for biological molecules:

Benedict's - blue to red/orange precipitate

Biuret- blue to lilac

Why do we need to test for the presence of protein?


Qualitative activity of immobilised enzymes i nvertase

Skills:

similar size beads

columns filled to same level

columns left for same length of time before opening the tap


Qualitative activity of immobilised enzymes i nvertase

Limitations of Benedict's:

does not test for other reducing sugars/only indicates the presence of glucose

not sensitive enough

colour comparison is subjective

if the time given is not long enough, it can give incorrect results

Advantages of having an immobilised enzyme only:

more product

no contamination by yeast

no sugar is used by the yeast for respiration

Advantages of having immobilised yeast:

little loss of enzyme

enzyme stays inside the yeast cell

don't have to extract the enzyme from the yeast

using a whole organism is cheaper


Qualitative activity of immobilised enzymes i nvertase

Quantitative task - Effect of NaCl on Activity of Yeast Cells:

0% - 20% NaCl When would you expect yeast to be most and least active?

If results from 5-20% are similar, how might you explain it?

If yeast remain active, what does this indicate about their tolerance of NaCl?

Which concentration of salt would you expect them to be most and least tolerant of?


Qualitative activity of immobilised enzymes i nvertase

Evaluative Task: Effect of NaCl on Activity in Yeast (0-20% NaCl)

Skills task - identification of how table should be laid out

Consider the following table showing the results of an unrelated experiment - the effect of humidity on the rate of transpiration:

Identify all the things wrong with the above table


Qualitative activity of immobilised enzymes i nvertase

Carbon dioxide can be made by yeast cells both aerobically and anaerobically

How do you think NaCl affects the rate of respiration? Think Unit 4!

Considering the answer to the above, why would you leave the yeast for several minutes before collecting data?

to allow time for the NaCl to affect the proteins/respiration/yeast

to allow time for the yeast to reach the desired temperature/30 degrees

The experiment required students to record the distance moved by yeast suspension up to a maximum of two minutes. Why would recording the volume of gas be an improvement?

gas could be collected over a longer time

What would you expect the control to be in this experiment?

What would you expect to happen to the pH during the experiment? Think back to AS Transport in Animals/respiration


Qualitative activity of immobilised enzymes i nvertase

Explain why scientists do replicates:

increase reliability

more easily identify anomalies

make comparisons more valid

enable us to undertake statistical tests

Explain the osmotic effect of NaCl - use AS knowledge!:

reduces water potential

water diffuses out of yeast cells

down the water potential

stops the yeast cell working/stops reactions


Qualitative activity of immobilised enzymes i nvertase

If NaCl affects the proteins involved in respiration, what type of protein might this be? enzyme/sodium:potassium pump/protein channel

What level of protein structure would these be and what can you remember about this level of protein from AS knowledge?

Tertiary/globular/3D/coiling of alpha-helix/ionic bonds


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