Why do organisms need enzymes?

As most chemical reactions are naturally very slow.

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The rate of chemical reactions increases with temperature.


Why don't we increase the temperature of our cells to increase the rate of chemical reactions?

  1. Heating our cells more would require a lot of energy.
  2. Higher temperatures could damage our cells.
  3. Higher temperatures would also speed up non-useful reactions.


We have already sort of done this, our body temperature is 37 °C, which is much higher than the environment, but any higher wouldn't be worth it. 

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What is a catalyst?

A catalyst is a substance that increases the speed of a chemical reaction without being used up or changed in the process.

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What is an enzyme?

An enzyme is a special type of catalyst (so it speeds up a chemical reaction without being used up) that is made by a living organism. We sometimes call them biological catalysts.

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What is the name of the special region of an enzyme that binds to the substrate? 

Active site.

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What do we call the complex that is formed when an enzyme binds to a substrate?

Enzyme-substrate complex.

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When discussing enzymes, what does 'complementary' mean?

A substrate must be complementary to the active site of the enzyme.


This means that it is the right match, or 'fits' the active site. 

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What is the lock and key model of enzyme action?

This was the first model that scientists proposed. They thought that in order for an enzyme to catalyse a reaction, the substrate had to fit perfectly into the active site.

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What is the induced fit model of enzyme action?

This is the improved model that scientists proposed. It states that in order for an enzyme to catalyse a reaction, the enzyme's active site actually changes shape slightly as it binds to the substrate.

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