2.3.2 3 Explain enzyme-substrate specificity.
An enzyme has a substrate that they are specific to that is the substance an enzyme acts on and makes more reactive. Also the enzyme has an active site that has a specific region on the enzyme that binds to a specific substrate that fits together sort of like a puzzle. One type of this is the lock and key model where the active site in the lock and key model, has a shape that is complementary to a specific substrate like the pieces of a puzzle. They then lock into each other like a key going into a lock perfectly. Also there is induced fit model where the active site of the enzyme changes shape to fit into the substrate, which induces this change.
Topic: 2 – The Chemistry of Life
Sub-topic: 2.3 – Enzymes
Page: 2
2.3.3 3 Explain the effects of temperature, pH and substrate concentration on
enzyme activity. (c.r. with 5.6.1)
Enzymes are sensitive to temperature changes and their activity increases as temperature increases. There activity doubles every 10 degrees C with optimum temperature at 40-45 degrees C. Also above the optimum temperature, enzyme activity decreases until the enzyme is destroyed or also known as denaturation. At 0 degrees Celsius enzymes are not denatured, but inactive. This inactivation is reversible, and can act again by increasing the temperature unlike denaturation that is irreversible. Most enzymes work best at neutral pH, but some digestive enzymes work at different optimum pH degrees, for example pepsin in the stomach works at an acidic pH. While intestinal enzymes work best at an alkaline pH. Changing the pH of the surrounding medium denatures enzymes and as the pH moves either way from seven being neutral the activity goes down. Next thing that affects enzymes is substrate concentration and as it increases, the rate of enzyme activity increases. The substrate concentration increases to a certain level and then it becomes constant. This is due to the enzyme concentration being a limiting factor. All of the active sites of enzymes become occupied by the substrate. If more enzymes are added at this stage of full reaction time then the rate of reaction increases again then stabilizes again.
Topic: 2 – The Chemistry of Life
Sub-topic: 2.3 – Enzymes
Page: 3
2.3.4 1 Define denaturation.
Denaturation is the process of destroying an enzyme by raising the temperature and disrupting there three-dimensional structure. This process is irreversible.
2.3.5 3 Explain the use of pectinase in fruit juice production, and one other
commercial application of enzymes in biotechnology.
Pectinase is used in fruit juice production to break down the acidity of the juices. In brewing the enzymes present in barley grains at germination are used to convert the starch stored in the grain to sugars and the proteins to amino acids. These converted things are then used by yeast for growth and alcohol production.
