13/03/2013 Jason Gao Rationale:
Digestion is the chemical breakdown of food into smaller components that are more easily absorbed. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones. When food enters into stomach, gastric juice starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. The pH value of hydrochloric in the stomach is 2, as the activity of pepsin is optimal, while it will lose its activity at pH 6.5 and above. However, pepsin will regain its activity at pH of 8. In the range of pH1 to pH6.5, pepsin will be most active at pH2, and starts to decrease its activity either higher or lower than pH 2. Therefore, pepsin can work well with hydrochloride solution, thus the purpose of the experiment is to find out the relationship between hydrochloride solution and protease enzyme pepsin. Research Question:
How is the activity of protease enzyme pepsin affected by different concentration of hydrochloride solution, which includes 0M (water), 0.05M, 0.1M, 0.2M, 0.3M and 0.4M? Variables:
Independent variables: different concentration of hydrochloride solution. * 0M, 0.05M, 0.1M, 0.2M, 0.3M and 0.4M
Dependent variables: extent that gelate blocks have been digested. * Can be measured by change in the mass of gelate blocks
* Temperature: The temperature of digestion environment will be controlled by keeping these solutions in the same area. This will mean that there is no variation in temperature between them. This in turn will keep the temperature of the solution constant. * Amount of pepsin: The pepsin used will be sourced from the same bottle for the entire experiment. This is to reduce any variation in levels of uncertainty of its concentration, which may affect the experiment. The pepsin will also be of the same temperature, as it will be collected from the same source. * Time: All gelate blocks should be added into the solution within the same time. This will reduce any variation of digestion time that may affect the experiment. * Volume of gelate blocks: All gelate blocks should be in the similar volume in order to avoid any variation in different value may take various time to start digestion. * Electronic balance: All gelate blocks should be measured on the same balance scale as every scale has different uncertainty. This is to reduce any variation in levels of mass uncertainty, which could affect the experiment.
* 20 ml of hydrochloride solution with 0.05M
* 20 ml of hydrochloride solution with 0.1M
* 20 ml of hydrochloride solution with 0.2M
* 20 m of hydrochloride solution with 0.3M
* 20 ml of hydrochloride solution with 0.4 M
* 350 ml of 2% pepsin solution
* Test tubes X 30
* A knife
* Gelate blocks
* Electronic balance
* 10 cm3 measuring cylinders X 4
Electronic balance| ± 0.002g|
10cm3 measuring cylinder| ± 0.1 cm3|
* Use a knife to cut 6 gelate blocks that are 1cm3, weigh their mass and record. * Add 10ml of 2% pepsin into each of the 30 test tubes.
* Add 2ml of water into 1 test tube.
* Add 2ml of 0.05M hydrochloride solution into 1 test tube * Add 2ml of 0.1M hydrochloride solution into 1 test tube * Add 2ml of 0.2M hydrochloride solution into 1 test tube * Add 2ml of 0.3M hydrochloride solution into 1 test tube * Add 2ml of 0.4M hydrochloride solution into 1 test tube * Put all gelate blocks in these test tube at the same time. * Wait for a few hours and take out gelate blocks, weigh and record their mass. Results:
Mass| 0M| 0.05M| 0.1M| 0.2M| 0.3M| 0.4M|
Before| 0.808g| 1.050g| 0.989g| 0.772g| 0.834g| 0.992g| After| 0.643g| 0.774g| 0.436g| 0.370g| 0.576g| 0.845g| Difference| 0.165g| 0.276g| 0.553g|...