==Key Stage 4==
{{#ev:youtube|https://www.youtube.com/watch?v=8Yqbu56ImXk}}
===Meaning===
Investigate the effect of [[pH]] on the rate of reaction for an [[enzyme]].
===Method===
*[[Dependent Variable]] - The antiseptic or antibiotic used.
*[[Independent Variable]] - Observe the growth of colonies.
*[[Control Variable]]s - The same quantity of antiseptic and antibiotic. The same spread of [[bacteria]] applied to the growth medium. Incubated for the same length of time. Incubated at the same temperature. Only one type of [[bacteria]] used.
#Agar plates prepared with ===Experiment Version 1=======Variables====*[[Independent Variable]] - [[pH]] of the buffered [[pH]] [[bacteriasolution]] will be supplied.#Mark *[[Dependent Variable]] - Time taken for the underside colour change to take place.*[[Control Variable]]s - The temperature of an agar plate into three sections making all solutions. The volume of all solutions.====Method====#Place [[Test Tube|test tubes]] containing a dot in the centre range of of each[[pH]] [[Buffer Solution|buffer solutions]], labeling them 1,2 a container of [[starch]] [[solution]] and 3 a container of [[amylase]] [[solution]] in a water bath at a [[temperature]] of around 30°C and writing your initials and the date on the agar platewait until all [[solution]]s reach that [[temperature]].#Spray the work space with disinfectant and wash your hands with antibacterial soapUse a [[pipette]] to place one drop of [[Iodine Solution]] into each depression in a [[Spotting Tile|spotting tile]].#Take Use a small circle clean [[pipette]] or [[syringe]] to place 2cm<sup>3</sup> of filter paper and soak it each [[pH]] buffer into one a [[Test Tube|test tube]].#Use a clean [[pipette]] or [[syringe]] to place 2cm<sup>3</sup> of starch solution into the three antiseptics/antibioticssame [[Test Tube|test tube]].#Place Use a clean [[pipette]] or [[syringe]] to place 1cm<sup>3</sup> of [[amylase]] [[solution]] into the circle onto same [[Test Tube|test tube]] and start the dot marked at the centre of a section[[stopwatch]].#Repeat steps 4 Use a clean [[pipette]] to remove a drop of the [[solution]] form the [[Test Tube|test tube]] and 5 ensuring drop it on the antiseptics are not mixed in any wayspotting tile every 10 seconds, beginning at 0 seconds.#Use two pieces of sellotape to attach Repeat this until the lid loosely to the top [[Iodine Solution|iodine solution]] in one of the agar plate (to ensure oxygen get in)depressions no longer turns black, but instead remains orange.#Incubate at 25°C for 48 hoursRepeat steps 2 to 7 until all different [[pH]] buffers have been tested.#Measure the diameter of the area in which Plot a graph with [[bacteriapH]] did not growon the x-axis and time taken on the y-axis.===References=======Edexcel====:[https://www.amazon.co.uk/gp/product/1292120193/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120193&linkCode=as2&tag=nrjc-21&linkId=572df39392fb4200db8391d98ae6314e ''Biology core practicals; pH and enzymes, pages 18-19, GCSE Combined Science, Pearson Edexcel '']