Enzymes

Pulling it all together

Enzymes are biological catalysts that help speed up the chemical reaction without being used up themselves. Most enzymes are proteins.

Enzyme Active Sites

Enzymes have an active site which is where the substrate molecules bind to the enzyme. Enzymes are highly specific and each type of enzyme will only bind to certain substrates. This is due to their unique 3D shape created by their level of structure. We say the substrate is complemenatry in shape.

Match each substrate to the correct substrate (drag and drop) and then click the key to check your work.

Substrates to Drag to the correct enzyme

Enzymes Activation Energy

Before a reaction can start, the reactants must have a certain amount of energy - this is known as the activation energy. When enzymes are present, they lower the activation energy of the reaction - i.e. the reaction can begin even though the reactants have less energy. Remember, reactants are the starting materials of the equation. Products are the end result of the reaction or what is made.

The graph below shows how enzymes affect the energy required for a chemical reaction to occur. Drag the correct label to each part of the graph. Then click the key to check your work.

Labels

Energy of products

Energy of reactants

Chemical reaction starts

Activation energy needed without enzyme

Activation energy needed with enzyme

Enzymes: pH

Before we look at how pH can affect enzyme function, let's review what pH is.

The pH scale is a way of ranking how acidic or alkaline a substance is. It goes from 0 - 14.

7.0

An acid is a solution that has a higher concentration of hydrogen ions than pure water. It does this by donating one of its hydrogen atoms through dissociation - i.e. putting more H+ ions into the solution. It has a pH of 0-6

A base is a solution that has a lower concentration of hydrogen ions than pure water. It does this by providing hydroxide ions (OH-) or another ion or molecule. This then removes H+ ions from the solution. It has a pH of 8-14

Enzymes: pH

Now let's look at how pH can affect enzyme function. Just like people have different tolerance for spicy food, enzymes have different pH tolerances. If the pH is too far beyond its optimal pH, the enzyme can become denatured and won't work anymore

Drag and drop the correct curve to the correct spot on the graph that shows how pH will affect activity. Then click the key to check your work.

Answer both questions based on the graph. Then click the key to check your work.

Enzymes: Temperature

Read the information below and then watch the video to see how temperature affects the reaction rate.

Enzymes: Temperature

Plot the results on the graph and then draw the curve using the pen (top right-hand side). Then click the key to check your work.

Optimal pH and temperature

The optimal pH or temperature will be found at the highest point on the graph. For gastric protease the optimal pH is 3. What is the optimal pH for Intestinal protease?

Answer:

Denatured Enzymes

When the temperature gets too hot the enzyme denatures. Notice the graph slope starts to trend down. What temperature has the enzyme started to denature?

Answer:

At about 55 degrees C the enzyme starts to denature and by 60 degrees the enzyme has stopped working entirely.

Enzyme C is able to function best in acidic and basic environments If enzyme A was placed in an environment with a pH of 9, it would slow or stop working.