Enzymes Flashcards
What is a catalyst
A substance which increases the speed of a reaction, without being changed or used up in the reaction
What is an enzyme
Catalysts produced by living things
What do enzymes in our body do?
Reduce the need for high temperatures in the body, as they only speed up useful chemical reactions (called metabolic reactions)
What are all enzymes?
Proteins, made up of chains of amino acids. These chains are folded into unique shapes so enzymes can do their job properly
What do chemical reactions involve
Things being split up or joined together
What is a substrate
A molecule changed in a reaction
What do all enzyme molecules have?
An active site
What is an active site?
The part where a substrate joins on to the enzyme
Why do enzymes only speed up one reaction?
For an enzyme to work, a substrate has to be the correct shape to fit into the active site. This is called a “lock and key” model.
What does changing the temperature change?
The rate of an enzyme-catalysed reaction. A higher temperature increases the rate, and a lower temperature decreases the rate
Why does a higher temperature increase the rate of an enzyme-catalysed reaction
More heat means the enzymes and the substrate particles have more energy, and move about more, so they are more likely to meet up and react - they have a higher collision rate.
What happens to an enzyme if the temperature is too hot?
Some of the bonds holding the enzyme together will break and the enzyme will lose its shape. It’s active site won’t fit the shape of the substrate any more, and it can’t catalyse the reaction so the reaction stops. The enzyme cannot function. It is said to be denatured, and it’s change in shape is irreversible.
What is the optimum temperature
The temperature the reaction goes fastest. It is the temperature before it gets too hot and starts to denature.
What is the optimum temperature for the most Important human enzymes?
37 degrees Celsius
What does the enzyme catalase do?
Catalysed the breakdown of hydrogen peroxide into water and oxygen
How can you measure how fast a product appears?
Use catalase to break down hydrogen peroxide solution into water and oxygen. The oxygen will then travel through a delivery tube from a test tube placed in a water bath into a measuring cylinder. The amount of oxygen produced per minute is measured
In measuring how fast a product appears, what variable might you want to control?
Enzyme concentration, pH, volume of solution
How to measure how fast a substrate disappears
Amylase converts starch to maltose. It is easy to detect starch (the substrate) using iodine solution; if starch is present, it will turn from browny-orange to blue-black. You can time how long it takes for the starch to disappear by regularly sampling the starch solution, and use the times to compare rates. By adjusting the water bath temperature you can see how temperature affects the activity of amylase.
How does pH affect enzymes?
If it’s too high or low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme. All enzymes have an optimum pH. It is often pH7 but not always
What pH does pepsin work best at?
Pepsin is used to break down proteins in the stomach so it works best at pH2 to suit the acidic conditions.
