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Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club The PiXL Club Practical Guide Biology Decay This document contains: Links to YouTube clips showing the practical procedure Information from examination boards AQA, OCR, Edexcel Potential examination questions and answers This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school. All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution. Commissioned by The PiXL Club Ltd. November 2016 www.pixl.org.uk The PiXL Club Ltd, Company number 07321607 © Copyright The PiXL Club Ltd, 2016

Required practical – exam boards AQA

Practical procedure: Decay Video Click on each of the tabs to take you to a YouTube clip. Please note these are external sites to PiXL, PiXL does not control the content of these sites. Image from: https://www.leaf.tv/articles/how-does-food-decompose/

Possible examination style questions When fat is broken down by enzymes what are the products? Explain why the indicator changes colour during this experiment. Bacteria secrete enzymes during the process of decay. What impact does temperature have on the rate of decay? What other factors affect the rate of decay? Explain how a gardener could provide optimum conditions for decay in their compost heap.

Possible examination style questions answers When fat is broken down by enzymes what are the products? ANS: Fatty acids Glycerol

Possible examination style questions answers Explain why the indicator changes colour during this experiment. ANS: Fatty acids are acidic Indicator shows the increase in acidity

Possible examination style questions answers Bacteria secrete enzymes during the process of decay. What impact does temperature have on the rate of decay? ANS: Increasing temperature increase the rate of decay Denaturation of enzymes/ death of organisms in high temperatures prevents decay

Possible examination style questions answers What other factors affect the rate of decay? ANS: Moisture/ availability of oxygen Availability of oxygen Presence of organisms such as earthworms/ maggots

Possible examination style questions answers Explain how a gardener could provide optimum conditions for decay in their compost heap. ANS: Place in sun/ warmth Turn regularly to aerate/ increase oxygen Keep moist/ add water Introduce organisms such as worms Adding bacteria

Key questions: Why have we added an enzyme? Why not leave the milk to decay ‘naturally’? Factors which affect enzyme action affect decay. Explain why. Name the factors which affect enzyme action. Explain how we could calculate the rate of decay form a graph showing decay over time. Explain why adding worms to a compost heap would increase the rate of decay. Explain the difference between aerobic and anaerobic decay. In this practical you are using an indicator to determine the pH change. Name another piece of equipment that could be used to monitor pH. Evaluate this practical. What improvements could you make?

Summary document A summary document is also available on Huddle which contains all the relevant information about this practical from the different examination boards. This document includes practical methods and other potential examination questions