(2) 1) The first experiment explored the influence of pH value on amylase. The independent variable was pH value, and the irrelevant variable was the condition that affected the experimental results, but it was not explored. In this experiment, the independent variables are the experimental temperature and the amount of salivary amylase.
2) Curve A is the result of Experiment 2. In experiment 2, the amount of starch solution is halved, so the amount of product is halved, so curve A is the result of experiment 2.
3) The abscissa corresponding to the lowest starch content in curves A and B is the same, because the optimum pH value of the same enzyme is certain and will not change with different concentrations. The function of enzyme needs an appropriate pH value. Too high or too low will change the spatial structure of the enzyme, make it denatured and inactivated, and cannot catalyze starch hydrolysis. When the pH value rises to a certain value, the starch content of the two groups of experiments is 100%.
(3) Five test tubes were added in step ① of the experiment, which were divided into five groups: A', B', C', D' and E'. In step ②, 1ml distilled water was added to replace 2% fresh salivary amylase solution, and the rest were tested according to the original experimental steps and conditions to verify whether starch would decompose at different pH values.
So the answer is:
(1) 1) In the experiment, the order of ③ and ④ is wrong, so ④ should be carried out before ③.
2) If the temperature is not set properly, step ⑤ should be changed to 37℃ constant temperature water bath.
(2) 1)pH value? Experimental temperature? Salivary amylase solution amount
2) Two? When the pH value is 7, the starch decomposition amount of curve A is half that of curve B..
3) The optimum pH value of the same enzyme is fixed and will not change with different concentrations? High pH denatures and inactivates salivary amylase, and cannot catalyze starch hydrolysis.
(3) In step ① of the experiment, five test tubes were added and divided into five groups: A', B', C', D' and E'. In step 2, 1mL distilled water was added instead of 2% fresh salivary amylase solution, and the rest were tested according to the original experimental steps and conditions.