1. Retardation Factors (Rf)
A chemical can also be identified by its retardation factor (Rf)
The formula is:
Rf = distance moved by sample
distance moved by solvent
The answer is never greater than 1.

2. AMINO ACID RF VALUES Mixture: Glycine, Leucine and tryptophan
Glycine = 0.26 Leucine = 0.73 Proline = 0.43 Serine = 0.27 Tryptophan = 0.66
Mixture:
Glycine, Leucine and tryptophan

3. Grab a whiteboard and pen

4. How do enzymes work?
For enzymes to have their effect, the active site and substrate have to physically meet, and the active site must be able to ‘fit’ or contain the substrate.
Which factors could affect the rate of enzyme controlled reactions?
Enzyme concentration
cofactors pH
Substrate concentration
Temperature
Inhibitors

5. Temperature
Can you explain what this graph shows in terms of substrate/enzyme interaction?
Increase in temperature gives molecules greater kinetic energy and they move around more quickly increasing the chance of molecules colliding. This causes an enzyme controlled reaction to increase its rate of reaction.
Above this temperature the increasing vibration of the molecules cause the hydrogen bonds to break and cause a change in the tertiary structure of the enzyme. This alters the active site of the enzyme.
The enzyme is then said to be DENATURED. This is a permanent change in the structure .

6. Effect of ph
pH refers to the concentration of H+ ions in a solution. These hydrogen ions (or hydroxyl ions) can interact with charged side chains of amino acids, and interrupt hydrogen bonds within the protein structure. This can have an effect on the shape of the active site of the enzyme.
The rate of an enzyme catalysed reaction will vary with changes in pH. Enzymes have a narrow optimum range and small changes in pH can affect the rate of reaction without affecting the structure of the enzyme.
At extremes of pH, the hydrogen bonding is affected and the 3D shape of the enzyme is altered and so is the shape of the active site.

7. Substrate concentration
What would a rate of enzyme controlled reaction look like with increasing substrate concentration?
If the amount of enzyme is constant, the rate of reaction will increase as the substrate increases, as more interactions can happen between the substrate and active site of the enzyme.
But there must come a point when all the enzyme’s active sites are working to full capacity i.e. all the active sites are filled.
Vmax

8. Enzyme Concentration
If there is an excess of substrate, the greater the concentration of enzymes, the quicker the rate of reaction. This is because there are more active sites available to catalyse the reaction. However if there is a limited supply of substrate, increasing the enzyme concentration will not further increase the rate of reaction, as there are already enough active sites to accommodate the available substrate molecules.

9. Biosensors
These devices are made up of a transducer and a biological element that may be an enzyme, an antibody or a nucleic acid. The ‘bioelement’ interacts with the sample being tested and the biological response is converted into an electrical signal by the transducer. 

10. Biosensors

11. Past Paper Question (5 mins)

12. Mark Scheme – Peer mark! a) 3 marks max
Enzyme/active site has a (specific) tertiary structure ü
Only glucose has the correct shape/ is complementary/ will fit ü
To active site ü
(Forming) enzyme-substrate complex ü
DO NOT allow ‘same’ shape! û
DO NOT allow active site is on the substrate û

13. Mark Scheme – Peer mark! b) 2 marks max
(Only detects glucose whereas) Benedict’s detects (all) reducing sugars/ example(s) ü
Provides a reading/ is quantitative/ Benedict’s only gives a colour/ doesn’t measure concentration/ is qualitative/semiquantitative ü
Is more sensitive/ detects low concentration ü
Red colour/ colour of blood masks result ü
Can monitor blood glucose conc. Continuouslyü
DO NOT credit ‘quicker’/ ‘more accurate’û