enzymes as catalysts

how enzymes work

Enzymes increase the rate of chemical reactions by reducing the amount of activation energy needed for reactants to start reacting. One way this can happen is modeled in the Figure 1.1. Enzymes arent changed or used up in the reactions they catalyze, so they can be used to speed up the same reaction over and over again. Each enzyme is highly specific for the particular reaction is catalyzes, so enzymes are very effective. A reaction that would take many years to occur without its enzyme might occur in a split second with the enzyme. Enzymes are also very efficient, so waste products rarely form. Q: This model of enzyme action is called the lock-and-key model. Explain why. A: The substrates (reactants) fit precisely into the active site of the enzyme like a key into a lock. Being brought together in the enzyme in this way helps the reactants react more easily. After the product is formed, it is released by the enzyme. The enzyme is now ready to pick up more reactants and catalyze another reaction. Click image to the left or use the URL below. URL:

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why living things need enzymes

Chemical reactions constantly occur inside the cells of living things. However, under the conditions inside cells, most biochemical reactions would occur too slowly to maintain life. Thats where enzymes come in. Enzymes are catalysts in living things. Like other catalysts, they speed up chemical reactions. Enzymes are proteins that are synthesized in the cells that need them, based on instructions encoded in the cells DNA.

digestive enzymes

More than 1000 different enzymes are necessary for human life. Many enzymes are needed for the digestion of food. Two examples are amylase and pepsin. Both are described in the Figure 1.2.

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instructional diagrams

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questions

enzymes work by providing activation energy.

a. true

-->  b. false

enzymes are used up in the reactions they catalyze.

a. true

-->  b. false

a human enzyme that helps digest starch is

a) pepsase.

b) starchase.

-->  c) amylase.

d) glucase.

which of the following statements about enzymes if false?

a) enzymes are highly specialized for the reactions they catalyze.

b) enzymes are very effective at speeding up reactions.

c) enzymes are very efficient at catalyzing reactions.

-->  d) enzymes usually result in the formation of waste products.

about 100 different enzymes are needed for human life.

a. true

-->  b. false

enzymes are

a) proteins.

b) encoded in dna.

c) made in the cells where they are needed.

-->  d) all of the above

diagram questions

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