Starter quiz
- An enzyme is an example of a catalyst. What do catalysts do?
- Slow down how quickly reactions happen.
- Speed up how quickly reactions happen. ✓
- Change the reactions that take place.
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- Enzymes are made up of chains of amino acids. Amino acids combined together make what type of molecule?
- Carbohydrate
- Protein ✓
- Fat (lipid)
- Vitamin
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The image is a simplified diagram of an enzyme. Which of the following would be the best label to use to replace 'A'?- substrate
- enzyme
- active site ✓
- substrate site
- complex
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- What do we mean by the rate of decomposition?
- How quickly populations of decomposers reproduce.
- How quickly populations of decomposers die.
- How quickly organic matter is broken down. ✓
- How many decomposers there are in a population.
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- Which of the following will help to increase the rate of decomposition?
- Warmer temperatures ✓
- Colder temperatures
- Wetter conditions ✓
- Dry conditions
- Reducing the levels of oxygen that is available
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- Why is decomposition in ecosystems important?
- It recycles important elements so they can be used by other organisms ✓
- Decomposers produce food for other all organisms in the rest of the food chain
- Decomposers provide a food source for plants
- Elements are used up during decomposition, this stops them from building up
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Exit quiz
- What is meant by pH?
- The colour that an indicator changes when added to a substance.
- How acidic or alkaline a substance is. ✓
- The acidity of a substance.
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- In the practical looking at the decomposition of milk by an enzyme, the point at which a colour change indicates the change in pH is known as the ...
- 'end point' ✓
- Cresol red is a solution which changes colour. What are solutions that change colour called?
- 'indicators' ✓
- What pH does milk become when it decays?
- alkaline
- acidic ✓
- neutral
- a gas
-
- When carrying out a practical activity, a precise, measurable and testable statement based on observations about how something works is called a ...
- prediction
- measurement
- observation
- hypothesis ✓
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- In the practical where you looked at the effect of temperature on the decomposition of milk using an enzyme, which variable is the independent variable?
- milk volume
- milk temperature ✓
- enzyme temperature
- pH of the milk
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- Use an enzyme (e.g. lipase) to decompose milk.
- Measure the change in pH as the milk is decomposed.
- Estimate the rate of decomposition by measuring the change in pH.
- Compare the rate of decomposition at different temperatures.
Common misconception
Several liquids are measured in this practical. The equipment used to measure the lipase should not be used to measure the liquids or the lipase may begin to digest fats before the practical starts.
To prevent contamination, ensure that the method is explained carefully and modelled through a demonstration or by watching the practical video.
Keywords
Enzyme - A protein which acts as a biological catalyst. This speeds up a reaction without being used up.
Active site - The part of an enzyme where the substrate binds.
Ph - A measure of how acidic or alkaline a solution is.
End point - The point at which a reaction is complete, often indicated by a change in colour of an indicator.
Hypothesis - A precise, measurable and testable statement based on observations about how something works.