Enzymes Worksheet (Answers)

Enzymes Enzyme Action Define the following terms Enzyme: A globular protein that speeds up the rate of a chemical reaction by lowering the activation …………………………………………………………………………………………………………………………………... energy (i.e. a biological catalyst) ………………………………………………………………………………………………………………………………………………….......... Substrate: A compound that binds to an enzyme’s active site and is converted into a product …………………………………………………………………………………………………………………………………... (the substrate is complementary in shape and chemical properties to the active site) ………………………………………………………………………………………………………………………………………………….......... Outline the steps in enzymatic binding and catalytic activity with the aid of the following diagram Enzyme and substrate collide in an appropriate orientation 1. …………………………………………………………………………………………………………………………………………………... (substrate binds to the enzyme’s active site) …………………………………………………………………………………………………………………………………………………... Enzyme and substrate form a complex, leading to catalysis 2. …………………………………………………………………………………………………………………………………………………... (enzyme-substrate interaction shows specificity) …………………………………………………………………………………………………………………………………………………... Substrate is converted into a product 3. …………………………………………………………………………………………………………………………………………………... (enzyme may stress the bonds within the substrate to catalyse this process) …………………………………………………………………………………………………………………………………………………... Enzyme and product dissociate 4. …………………………………………………………………………………………………………………………………………………... (enzyme is not consumed by the reaction and may be re-used) …………………………………………………………………………………………………………………………………………………... Identify factors that can affect an enzyme’s molecular motion and collision with a substrate Temperature - increases the kinetic energy of particles, leading to more frequent collisions ………………………………………………………………………………………………………………………………………………….......... Substrate concentration - increases frequency of collisions with enzyme ………………………………………………………………………………………………………………………………………………….......... Enzyme concentration - increases frequency of collision with substrate ………………………………………………………………………………………………………………………………………………….......... Distinguish between the ‘lock and key’ and ‘induced fit’ models of enzyme specificity Lock and Key Model: Substrate and active site are complementary in both shape and chemical properties ………………………………………………………………………………………………………………………………………………….......... Means that enzymes are specific for the reaction they catalyse ………………………………………………………………………………………………………………………………………………….......... Induced Fit Model: Active site is not a perfect fit, but undergoes a conformational change in shape to accommodate substrate ………………………………………………………………………………………………………………………………………………….......... This stresses bonds in the substrate (promoting catalysis) and gives rise to broad specificity ………………………………………………………………………………………………………………………………………………….......... Temperature Enzyme Activity Enzyme Activity Enzyme Activity Explain the effect of different factors on enzyme activity pH Substrate Concentration At low temperatures there is insufficient activation energy for reaction to proceed Temperature: …………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………….......... As temperatures increase, the rate of reaction increases (higher kinetic energy = more collisions) ………………………………………………………………………………………………………………………………………………….......... At a certain optimum temperature, the rate of reaction will plateau (i.e. peak efficiency) ………………………………………………………………………………………………………………………………………………….......... Above this temperature, the enzyme will begin to denature and rate of reaction will decrease Enzymes have an optimal pH at which the rate of reaction is highest pH: …………………………………………………………………………………………………………………………………………………. At higher and lower pH levels, activity will decrease (leading to a bell-shaped curve) ………………………………………………………………………………………………………………………………………………….......... This is because pH affects the charge and solubility of the enzyme ………………………………………………………………………………………………………………………………………………….......... The change in the enzyme’s chemical properties causes it to denature (lose tertiary structure) ………………………………………………………………………………………………………………………………………………….......... Enzyme activity increases as substrate concentration increases Substrate Concentration: ………………………………………………………………………………………………………………… This is because there are more substrate particles, leading to a higher rate of successful collisions ………………………………………………………………………………………………………………………………………………….......... At a certain point, the rate of enzyme activity will plateau ………………………………………………………………………………………………………………………………………………….......... This is because all enzyme active sites are occupied (the solution is saturated) ………………………………………………………………………………………………………………………………………………….......... Enzyme Application Explain the benefits of immobilized enzymes in industry, with examples Immobilised enzymes have been fixed to a static surface in order to increase enzyme efficiency ………………………………………………………………………………………………………………………………………………….......... • Enzyme concentrations are conserved, as the enzyme is not dissolved - hence it can be re-used ………………………………………………………………………………………………………………………………………………….......... • Product is more easily separated from enzyme, as the enzyme is fixed in position ………………………………………………………………………………………………………………………………………………….......... Examples of immobilised enzymes in industry include in food production, medicine and biofuel production ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Outline the production of lactose-free milk and its advantages Production of Lactose-Free Milk: Lactase is fixed to agarose beads (lactase purified from yeast or bacteria) ………………………………………………………………………………………………………………………………………………….......... Milk is passed over the immobilised enzyme, becoming lactose-free ………………………………………………………………………………………………………………………………………………….......... Advantages of Lactose-Free Milk: Provides a source of milk and other dairy products for lactose-intolerant individuals ………………………………………………………………………………………………………………………………………………….......... Increases sweetness in the absence of artificial sweeteners (monosaccharides are sweeter in taste) ………………………………………………………………………………………………………………………………………………….......... Reduces the crystallisation of ice-creams (monosaccharides are more soluble, less likely to crystallise) ………………………………………………………………………………………………………………………………………………….......... Suggest ways of measuring the following enzyme-catalysed reactions 1. The conversion of hydrogen peroxide to oxygen gas (by catalase) • Measure time taken for an enzyme-soaked disc to rise in solution ………………………………………………………………………………………………………………………………………………….......... • Measure gas formation via pressure change (with data logger) or displacement of a syringe cap ………………………………………………………………………………………………………………………………………………….......... 2. The breakdown of starch into maltose (by diastase) • Measure colour change with a colorimeter (starch is stained purple by iodine) ………………………………………………………………………………………………………………………………………………….......... • Measure volume change via dialysis tubing (starch is impermeable to tubing, maltose is not) ………………………………………………………………………………………………………………………………………………….......... 3. The digestion of pectin in cell walls (by pectinase) • Measure volume of liquid produced as a consequence of the breakdown in cell wall ………………………………………………………………………………………………………………………………………………….......... • Measure the digestion of pectin via percentage weight change …………………………………………………………………………………………………………………………………………………..........