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1 of 23© Boardworks Ltd 2011 Enzymes
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3 of 23© Boardworks Ltd 2011 What’s the missing link? What is the link between digestion, photosynthesis, respiration and DNA replication? They all depend on enzymes.
4 of 23© Boardworks Ltd 2011 What are 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 of 23© Boardworks Ltd 2011 What are enzymes made of? 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 of 23© Boardworks Ltd 2011 Enzymes: true or false?
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8 of 23© Boardworks Ltd 2011 Fussy enzymes? Why are enzymes so specific in their reactions?
9 of 23© Boardworks Ltd 2011 Why are enzymes so specific? 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.
10 of 23© Boardworks Ltd 2011 What happens at the active site? 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 enzyme + ↔ + ↔↔ +
11 of 23© Boardworks Ltd 2011 The lock and key model
12 of 23© Boardworks Ltd 2011 Why do enzymes speed up reactions? Enzymes speed up reactions by lowering the activation energy (E a ) of a reaction. The activation energy is the energy needed to start a reaction. Different reactions have different activation energies. reaction (time) energy (kJ) E a with enzyme E a without enzyme
13 of 23© Boardworks Ltd 2011 Factors affecting enzymes The rate of enzyme-catalyzed reactions depends on several factors. What are some of these? All enzymes work best at only one particular temperature and pH: this is called the optimum. Factors that affect the rate of a reaction include: substrate concentration temperature Different enzymes have different optimum temperatures and pH values. pH enzyme concentration surface area pressure.
14 of 23© Boardworks Ltd 2011 Factors affecting enzymes If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes. normal denatured heat pH This affects the shape of the active site and means that the enzyme will no longer work. When this happens the enzyme is denatured.
15 of 23© Boardworks Ltd 2011 Enzymes and temperature
16 of 23© Boardworks Ltd 2011 Temperature and reaction rate 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 Q 10 for any reaction over a 10°C interval with the following formula: Q 10 = rate at lower temperature rate at higher temperature
17 of 23© Boardworks Ltd 2011 Enzyme inhibitors
18 of 23© Boardworks Ltd 2011 Identifying enzyme terms
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20 of 23© Boardworks Ltd 2011 Glossary
21 of 23© Boardworks Ltd 2011 Anagrams
22 of 23© Boardworks Ltd 2011 Name the structure
23 of 23© Boardworks Ltd 2011 Multiple-choice quiz
ENZYMES. Enzymes are biological catalysts, which work to speed up a chemical reaction. Without enzymes, several reactions in cells would never occur or.
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PIG - enzymes. What are enzymes?  3 of the following: Biological catalysts Globular proteins Increase the rate of (chemical) reaction Complimentary.
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1 of 39© Boardworks Ltd 2007 Kinetics. © Boardworks Ltd of 39.
Enzymes What are enzymes? Specialized proteins What do they do? They act as catalysts in chemical reactions in our bodies.
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