AccelePrep for the ACT Test 2nd Edition Student Text

188 • S URGE TO S UCCESS ! S CIENCE T EST P REP

ANSWERS

1. (B) 6FLHQFH 6FLHQWLÀF ,QYHVWLJDWLRQ $QDO\VLV The experiments investigate enzyme activity. By comparing experimental groups (enzyme present) with control groups (only water present) under otherwise identical conditions, any differences in the experimental results are attributable to the presence of the enzyme in the experimental groups. Did you note the differences in the experiments in your big picture reading? 2. (H) 6FLHQFH ,QWHUSUHWDWLRQ RI 'DWD $QDO\VLV Although salivary amylase is most effective when the pH level is 7, the enzyme begins to convert starch to sugar at pH levels of 5 and 9—after 15 minutes, low levels of sugar appear, suggesting the onset of starch digestion; after 60 minutes, moderate levels of starch remain and moderate levels of sugar have accumulated. 3. (D) 6FLHQFH ,QWHUSUHWDWLRQ RI 'DWD $QDO\VLV Experiment 1 indicates that the digestion of starch is the fastest (after 3 minutes, some starch is gone and sugar is already present) and the most thorough (after 15 minutes, all of the starch has become sugar) at a pH level of 7. Experiment 2 shows similar results when the temperature is 37°C. Did you notice these trends in your big picture reading?

4. (H) 6FLHQFH 6FLHQWLÀF ,QYHVWLJDWLRQ $QDO\VLV To investigate the effects of enzyme concentration on digestion, all variables must be kept the same for each beaker except for the amount of enzyme. 5. (B) 6FLHQFH 6FLHQWLÀF ,QYHVWLJDWLRQ $QDO\VLV Originally, Experiment 2 was carried out at an “optimal pH” (probably close to 7). Since a pH level of 5 is less than optimal, as indicated by Experiment 1, the action of salivary amylase in the proposed experiment would probably be Ž‡•• ‡ˆϐ‹…‹‡– ”‡‰ƒ”†Ž‡•• ‘ˆ –‡’‡”ƒ–—”‡Ǥ