Certain plants that reproduce sexually contain an enzyme called pyrophosphatase. This enzyme plays a role in ensuring self-incompatibility, which is a mechanism that prevents a plant from fertilising itself. The selective advantage of self-incompatibility is that more cross-breeding can occur within a species, which has long term benefits for evolution and for maintaining a large pool of alleles.
Known volumes of pyrophosphatase and substrate can be mixed in a cuvette with a dye that starts as colourless and develops into a blue colour over time. The rate of colour development can be measured in a colorimeter by measuring the absorbance of light at a wavelength of 620 nm (red light).
The graph shows the mean rate of reaction of pyrophosphatase measured over five repeats at 20°C.
State why the wavelength of 620 nm was selected for this experimental measurement.
A solution containing sucrose and sucrase was divided equally between two test tubes. One test tube (A) was heated to a temperature of 85°C, and the other (B) was kept at 37°C, as shown in the diagram below. Both test tubes were monitored for 30 minutes.
i)
Identify which test tube(s) would contain monosaccharides.
A significant amount of research has been conducted on the enzyme composition of extremophile microorganisms, in order to discover new enzymes that can be used in the home in extreme conditions. One such organism, Planococcus halocryophilus, is a psychrophile (it grows at cold temperatures around 0°C). Trials with the enzymes of P. halocryophilus have discovered applications of these enzymes in the detergent industry.
Suggest how these trial results are encouraging for the laundry detergent industry.
Papain is a proteolytic enzyme derived from the papaya fruit. It has been used in contact lens cleaning solutions to remove denatured protein-containing deposits that accumulate on the surfaces of contact lenses during long periods of wear. The periodic removal of protein deposits increases wearer comfort and extends the wearing time.
The main protein component of tear film fluid is lysozyme.
Suggest a reason for the presence of lysozyme in tear film fluid.
Lysozyme and other proteins present in tear film fluid can denature rapidly when in contact with contact lens material. This denatured material loses its original function and forms deposits on the lens surface.
i)
Describe the mode of action of papain against the denatured protein deposits on the surfaces of the contact lenses.
[1 mark]
ii)
Explain the effect that the action of papain would have on these contact lens deposits.
The enzyme glucoamylase is a catabolic enzyme that hydrolyses the α-1,4 glycosidic bonds in starch to produce glucose for use in industry.
The enzyme used in this process can be covalently bonded to a substrate of beads to become immobilised. Once immobilised they are able to be used in 11 successive cycles before they need to be replaced.
Suggest a potential method that could be used to determine whether the immobilised enzymes need to be replaced.
Glucoamylase has an optimum temperature of 60°C when free in solution, however when it is immobilised the optimum temperature is raised to between 60°C and 80°C.
Explain why this is an advantage to the manufacturers using this immobilised enzyme to produce glucose.
Some scientists think that the reason for the increase in optimum temperature of the immobilised enzyme is due to the covalent bonding between the enzyme and the beads that hold them in position. They believe that covalent bonding helps to reduce the influence of high kinetic energy on the bonds within the enzyme structure.
Suggest how this would cause the enzyme to have a higher optimum temperature.
