Enzymes

What do living things have thousands of going on all the time?

Chemical reactions inside the body

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How are reactions usually done quicker and what does that mean?

By raising the temperature. This would speed up the useful reactions but also the unwanted ones too.

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What do living things produce and what do they act as?

Enzymes, which act as biological catalysts.

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What are enzymes?

Catalysts produced by living things.

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What do emzymes do?

Reduce the need for high temperatures and to therefore speed up the useful chemical reactions in the body.

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What is a catalyst?

A catalyst is a substance which INCREASES the speed of a reaction, without being CHANGED or USED UP in the reaction.

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All enzymes are proteins. How do they work and what do they do?

They all work i the same way to catalyse various reactions. They can work inside or outside cells.

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Name examples or where they work and whether they work inside or outside the cell.

DNA replication (Inside), Protein synthesis (Inside), Digestion (Inside/Outside)

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How do enzymes work through DNA replication?

Where enzymes work inside a cell, to help copy a cell's DNA before it divides by mitosis or meiosis.

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How do enzymes work through protein synthesis?

Where enzymes hold amino acids, inside a cell in place and form bonds between them.

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How do enzymes work through digestion?

Various enzymes are secreted into the gut to digest different food molecules.

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What do enzymes have and why?

Special shapes so they can catalyse reactions.

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What do chemical reactions usually involve?

Things either being split apart or joined together.

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What is the substrate?

The molecule changed in the reaction.

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What does every enzyme have and why?

An active site - the part where the enzyme joins on to its substrate to catalyse the reaction.

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How many substrates do enzymes usually work with?

One. Enzymes have a high specificity for their substrate.

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What does the substrate have to fit into and what happens if it doesn't? What is this called?

The substrate has to fit into the active site. If the substrate's shape doesn't match the active site's shape, then the reaction won't be catalysed. This is called the 'lock and key' mechanism, because the substrate fits into the enzyme.

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Describe the experiment to measure the rate of an enzyme-controlled reaction. Describe what you do first.

Use amylase as the enzyme and starch as the substrate.

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What happens next? (Enzymes)

Amylase catalyses the breakdown of starch, so you can time how long it takes for the starch to disappear.

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How can you time how long it takes for the starch to disappear?

Take a drop of the amylase and starch mixture and put it onto a drop of iodine solution on a spotting tile. Record the colour change - it'll turn blue-black if starch is present. Note the time when iodine solution no longer turns blue-black.

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What does it mean when the iodine solution no longer turns blue-black?

The starch has been broken down by the amylase.

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What you can do with the times?

You can use the times to compare reaction rates under different conditions.

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Enzymes

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