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Boardworks GCSE Additional Science: Biology

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Presentation on theme: "Boardworks GCSE Additional Science: Biology"— Presentation transcript:

1 Boardworks GCSE Additional Science: Biology
Enzymes Enzymes

2 Boardworks GCSE Additional Science: Biology
Enzymes

3 What’s the missing link?
Boardworks GCSE Additional Science: Biology Enzymes What is the link between digestion, photosynthesis, respiration and DNA replication? They all depend on enzymes.

4 Boardworks GCSE Additional Science: Biology
What are enzymes? Boardworks GCSE Additional Science: Biology Enzymes Enzymes are biological catalysts – they speed up the chemical reactions that take place inside all cells, but without being used up in the process. There are many thousands of different types of enzyme, and each one catalyzes a different reaction. Cells create enzymes based on instructions carried in the cell’s genes.

5 What are enzymes made of?
Boardworks GCSE Additional Science: Biology Enzymes Enzymes are protein molecules, and so are made up of amino acids. Most enzymes contain between 100 and 1,000 amino acids. These amino acids are joined together in a long chain, which is folded to produce a unique 3D structure. Different types of enzymes have different shapes and functions because the sequence and type of amino acids in their structure is different.

6 Boardworks GCSE Additional Science: Biology
Enzymes: true or false? Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This true-or-false activity could be used as a plenary or revision exercise on enzymes, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

7 Boardworks GCSE Additional Science: Biology
Enzymes

8 Boardworks GCSE Additional Science: Biology
Fussy enzymes? Boardworks GCSE Additional Science: Biology Enzymes Why are enzymes so specific in their reactions? Teacher notes This illustration contains several discussion points relating to enzymes, including: Thermostat Different enzymes have different optimum temperatures. Beyond their optimum temperature enzymes denature (breakdown). The thermostat in the illustration is set to a high temperature, and most of the enzymes seem uncomfortably hot. Arguments The shape of an enzyme’s active site determines which reactants it can bond with. In this illustration, incompatible enzyme–reactant pairs are shown either arguing or ignoring each other. ‘The happy couple’ Enzymes and reactants that are compatible are said to fit together like a ‘lock and key’. The happy couple shown in the bottom left of the illustration have corresponding shapes, and seem to be reacting well to each other in the warm environment.

9 Why are enzymes so specific?
Boardworks GCSE Additional Science: Biology Enzymes Enzymes are very specific about which reactions they catalyze. Only molecules with exactly the right shape will bind to the enzyme and react. These are the reactant, or substrate, molecules. The part of the enzyme to which the reactant binds is called the active site. This is a very specific shape and the most important part of the enzyme. Photo credit: JC Revy / Science Photo Library The image shows a molecular computer graphics image of ribonuclease A, an enzyme involved in the destruction of messenger RNA (mRNA) in the cytoplasm of bacteria. At left is its substrate, shifted away from the active site. Enzymes are biological catalysts, proteins that speed up the rates of reactions within cells. Each enzyme is specific for a particular reaction; interaction occurs (typically as a weak bond) between an active site on the enzyme & a reactant (or substrate) due to the arrangement of mutually attractive groups of atoms. This image displays the molecular surface (blue) & polypeptide chain: colours are used to represent the polarity of constituent amino acids.

10 What happens at the active site?
Boardworks GCSE Additional Science: Biology Enzymes In the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site. The enzyme is the lock, and the reactant is the key. + + enzyme reactant + enzyme–reactant complex products

11 Boardworks GCSE Additional Science: Biology
The lock and key model Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This four-stage animation demonstrates the principles of the ‘lock and key’ model. While showing the animation, the specific shape of the active site could be highlighted. Suitable prompts could include: What is special about the shape of the active site? Is the enzyme the ‘lock’ or the ‘key’?

12 Why do enzymes speed up reactions?
Boardworks GCSE Additional Science: Biology Enzymes Enzymes speed up reactions by lowering the activation energy (Ea) of a reaction. The activation energy is the energy needed to start a reaction. Different reactions have different activation energies. reaction (time) energy (kJ) Ea without enzyme Ea with enzyme Teacher notes See the Boardworks GCSE Additional Science Chemistry Changing Reaction Rates presentations for more information on activation energy.

13 Factors affecting enzymes
Boardworks GCSE Additional Science: Biology Enzymes The rate of enzyme-catalyzed reactions depends on several factors. What are some of these? Factors that affect the rate of a reaction include: temperature substrate concentration pH surface area enzyme concentration pressure. All enzymes work best at only one particular temperature and pH: this is called the optimum. Different enzymes have different optimum temperatures and pH values.

14 Factors affecting enzymes
Boardworks GCSE Additional Science: Biology Enzymes If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes. This affects the shape of the active site and means that the enzyme will no longer work. When this happens the enzyme is denatured. denatured normal heat pH The information on this slide is higher tier for OCR 21st Century GCSE Additional Science and OCR Gateway GCSE Additional Science.

15 Enzymes and temperature
Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This five-stage animation could be used as a precursor to running the experiment in the lab, or as a revision exercise.

16 Temperature and reaction rate
Boardworks GCSE Additional Science: Biology Enzymes As the temperature increases, there are more collisions between enzymes and reactants. This increases the rate of reaction. At a certain point, the temperature gets too high and the enzymes are denatured. The enzymes can no longer bind with reactants. We can work out the Q10 for any reaction over a 10°C interval with the following formula: Teacher notes Students may need to be reminded that the Q10 temperature coefficient is the measure of the rate of change of a system as a result of increasing the temperature by 10°C. You might like to have students apply this equation to the reaction on the previous slide. Show them either the graph or the table from the final stage of the animation and ask them to find the Q10 of the reaction. The information on this slide is higher tier for OCR 21st Century GCSE Additional Science and OCR Gateway GCSE Additional Science. rate at higher temperature Q10 = rate at lower temperature

17 Boardworks GCSE Additional Science: Biology
Enzyme inhibitors Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This four-stage animation shows how competitive and non-competitive inhibitors block the action of enzymes by either binding to, or altering the shape of, their active site.

18 Identifying enzyme terms
Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This matching activity could be used as a plenary or revision exercise on enzymes. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.

19 Boardworks GCSE Additional Science: Biology
Enzymes The worksheet ‘Enzymes’ accompanies this presentation.

20 Boardworks GCSE Additional Science: Biology
Glossary Boardworks GCSE Additional Science: Biology Enzymes Teacher notes activation energy – The energy needed to start a chemical reaction. active site – The part of the enzyme into which the reactant molecule fits. catalyst – A substance that changes the rate of a reaction without being used up. denatured – The state of an enzyme when it has been irreversibly damaged and has changed shape. enzyme – A biological catalyst. inhibitor – A molecule that decreases the rate of enzyme-catalysed reactions. lock and key – A model of how enzymes work and the importance of their shape. optimum – The temperature and pH at which an enzyme-catalyzed reaction proceeds at the fastest rate. reactant – The substrate molecule that binds to and reacts with the enzyme. respiration – The series of reactions that release energy from glucose, in the presence of oxygen.

21 Boardworks GCSE Additional Science: Biology
Anagrams Boardworks GCSE Additional Science: Biology Enzymes

22 Boardworks GCSE Additional Science: Biology
Name the structure Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This activity could be used to check students’ understanding of the lock and key model.

23 Boardworks GCSE Additional Science: Biology
Multiple-choice quiz Boardworks GCSE Additional Science: Biology Enzymes Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of enzymes. The questions can be skipped through without answering by pressing the forward arrow. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.


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