enzymes

Question 1

definition of enzymes

Answer 1

enzymes are biological catalysts. a catalyst is a chemical that speeds up a reaction without it being used up itself.

Question 2

why are enzymes necessary

Answer 2

temperatures inside organisms are low (37) and without catalysts most of the reactions that happen in cells would be far to slow to allow life go on. enzymes speed them up.

Question 3

structure of enzyme

Answer 3

1. the molecule that an enzyme acts on is called it substrate.
2. each enzyme has a small area o. its surface called the active site.
3. the substrate attaches to the active site of the enzyme.
4. the reaction then takes place and products are formed.
5. when the substrate joins up with the active site it lowers the energy needed for the reaction to start, allowing the products to be formed more easily and faster.
6. the substrate fits into the active site like a key fitting into a lock.

Question 4

factors affecting enzymes

Answer 4

temperature -
as the enzyme is heated up to the optimum temperature, the rise in temperature increases the rate of the reaction. this is because higher temperatures give the molecules of the enzyme more kinetic energy, so they can collide more often, more collisions mean that the reaction will occur more frequently. However, above the optimum, temperature starts to have another effect. enzymes are made of protein. proteins are broken down by heat. From 40 degrees upwards the heat destroys the enzyme and becomes denatured. denaturing changes the shape of the active site and the substrate ca no longer fit to it. denaturing is permanent and the enzyme molecules will no longer catalyze the reaction.
pH-
The pH around the enzyme is also important. The pH inside cell is neutral, and most enzymes have evolved to work best at this pH. At extremes of pH, either side of neutral, the enzyme activity decreases. Either side of the optimum, the pH affects the structure of the enzyme molecule and changes the shape of its active site, so that the substrate will not fit into it so well.

Question 5

Practical: an investigation into the effect of temperature on the activity of amylase

Answer 5

The digestive enzyme amylase breaks down starch into the sugar maltose.
Spotify, the solution are placed into the dips on the spotting tile. Using a syringe 5 cm³ of starch suspension is placed in one boiling tube, and 5 cm³ of amylase solution in another tube, using a different syringe. The beaker is filled with water at 20°. Both boiling tubes are placed in the beaker of water for five minutes and the temperature is recorded.
the amylase solution is then poured into the starch suspension leaving the tube containing the mixture in the water bath. Immediately, a small sample of a mixture is removed from the tube with a pipette and added to the first drop of violence solution on the spotting tile. The color of the iodine solution is recorded.
A sample of a mixture is taken every 30 seconds for 10 minutes and tested for starch until the iodine solution remains yellow showing that all the starch is used up.