Enzymes Objectives what is an enzyme? How do enzymes speed up reactions? What changes the rate of enzyme controlled reactions?

What are enzymes??? Enzymes are proteins. Enzymes speed up chemical reactions in our cells – biological catalysts. Enzymes do not change the overall reaction in anyway except to make it happen faster. Each enzyme catalyses a specific type of reaction. Thousands of chemical reactions take place in our cells. We need these reactions to take place quickly to keep us alive. Luckily for us we have chemicals called enzymes. Enzymes make reactions happen at a faster rate. Chemicals that speed up reactions are called catalysts

Enzymes have a specific shape Active site Enzymes work on substances called substrates. Your enzymes are large protein molecules. They are made of long chains of amino acids, folded and coiled to give a molecule with a very special shape. The enzyme usually has a hole or indentation in it. The special molecule allows other molecules to fit into the enzyme. We call this an active site. The shape of the enzyme is vital for the way it works. The reaction takes place on a part of the surface of the enzyme called active site. Enzymes have a specific shape

Breakers and Builders Enzymes come in two main types: Breakers Sometimes we need to break down larger molecules into smaller ones. Breaker enzymes speed these reactions up e.g. Digestion. Builders In other reactions small molecules are joined to make larger ones. Builder enzymes speed these reactions up.

How do chemical reactions take place??? Activation energy – minimum amount of energy particles must have to be able to react. You will make a reaction more likely if you can make it: More likely that reacting particles bump into each other, Increase the energy of these collisions, or Reduce the activation energy. Enzymes lower the activation energy needed to make a reaction take place. Chemical reactions can only take place when different particles collide. The reacting particles dont just have to bump into one another, they have to collide with enough energy to react.

Lock and Key Hypothesis How do enzymes work? Lock and Key Hypothesis

Lock and key hypothesis + ↔ Enzymes work on substances called substrates. Your enzymes are large protein molecules. They are made of long chains of amino acids, folded and coiled to give a molecule with a very special shape. The enzyme usually has a hole or indentation in it. The special molecule allows other molecules to fit into the enzyme. We call this an active site. The shape of the enzyme is vital for the way it works. The reaction takes place on a part of the surface of the enzyme called active site. The substrate (reactant) of the reaction fits into the shape of the enzyme. You can think of it like a lock and key. Once it is in place the enzyme and substrate can bind together = the enzyme-substrate complex. Then the reaction takes place rapidly and the products are released from teh surface of the enzyme. Enzymes can be used over and over again. They will keep working until all the substrate is used up. enzyme enzyme ↔ enzyme-reactant complex ↔ + + reactant products

All enzymes have 5 important properties: They are all proteins. Each enzyme controls one particular reaction. They can be used again and again. They are affected by temperature. They are affected by pH. Enzymes usually works best under very specific conditions of temperature and pH. This is because anything which affects the shape of the active site also affects the ability of the enzyme to speed up a reaction.

Effect of temperature on enzyme action The chemical reactions which take place in living cells happen at relatively low temperatures. Like most other chemical reactions, the rate of enzyme controlled reactions increases with an increase in temperature. The enzyme and substrate particles move faster as the temperature increases, so this makes them more likely to collide with enough energy to react. However, this is only true up to temperatures of about 40 degrees celsius. After this the protein structure of the enzyme is affected by the temperature. The long amino acid chain begins to unravel. As a result the shape of the active site changes (show this with the beads – ask Joss). We say that the enzyme has been denatured. It can no longer act as a catalyst, so the rate of the reaction drops dramatically. Most human enzymes work best at 37. Why do you think this is? Not all enzymes work best at around 40 degrees c. Bacteria living in hot springs work at temps over 80 and higher. On the other hand some bacteria which live in very cold deep sea have enzymes working effectively at 0 degrees and below.

Enzymes are not killed!!!!!!!!! Enzymes are molecules not living things. They do NOT die, they become DENATURED.

Effect of pH on enzyme action Enzymes have their effect by binding the reactants to a specifically shaped active site in the protein molecule. Anything which changes the shape of this active site stops the enzyme from working. Temperature is one thing which changes the shape of a protein molecule. The surrounding pH is another. The shape of the enzymes is the result of forces between the different parts of the protein molecule which hold the folded chains in place. A change in pH affects these forces and changes the shape of the molecule. As a result the active site is lost, so the enzyme can no longer act as a catalyst. Different enzymes have different pH levels at which they work their best and a change in the pH can stop them working completely.

Role of Enzymes Vital to all living cells. Enzymes catalyse processes such as respiration, photosynthesis and protein synthesis in all living cells. This is why it is dangerous if your temperature gets too high. Once your temperature reaches 41 degrees your enzymes start to be denatured adn you will soon die.