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Are Enzymes Specific for Their Substrates?
Rubric
Contributed by: The State University of New York
New York State Education Department (NYSED)
1996 Administration

Maximum Score - 15 Points


Data Table 3 points total

Sample data table showing correct results of testing the specificity of the enzyme lactase.


Title: Testing for Enzyme Specificity

Spot Substance Tested Glucose present? yes no
1 Glucose solution X  
2 Enzyme solution   X
3 Unknown A solution   X
4 Unknown B solution   X
5 Unknown C solution   X
6 Unknown A solution + Enzyme solution   X
7 Unknown B solution + Enzyme solution X  
8 Unknown C solution + Enzyme solution   X

Criteria:

Allow 1 point for each of the following;
  • Appropriate title present.
  • Substances tested are identified.
  • Results of tests recorded and paired. Accuracy of results are not considered here.


Question 1 - Indicates Need for Control 2 points total

Criteria:
2 points   Correct/generally states that well #2 acts as a control to show that the enzyme solution does not contain glucose. Answer should be written in complete sentences.
1 point   Correct statement, but not in complete sentences.
0 points   Incorrect responses, even if it is in complete sentences, or no response provided.


Question 2 - Explain Enzyme Specificity 2 points total

Criteria:
2 points   Correctly states that enzyme activity was indicated by the presence of glucose in spot 7. Answer should be written in complete sentences.
1 point   Correct statement, but not in complete sentences.
0 points   Incorrect responses, even if it is in complete sentences, or no response provided.


Question 3 - Lactose as Specific Substrate/Disaccharide 1 point total

Criteria:
1 point   Correctly names lactose as the specific substrated/disaccharide on which lactase acts.
0 points   Incorrect responses, or no response provided.


Question 4 - Identifies Substrate 1 point total

Criteria:
1 point   Correctly identifies depression/spot/well 7 as containing the substrate.
0 points   Incorrect responses, or no response provided.


Question 5 - Explain Chemical Activity 1 point total

Criteria:
2 points   Correctly explains that in spot 7 chemical activity occurred as indicated by a positive test for glucose. Answer should be written in complete sentences.
1 point   Correct statement, but not in complete sentences.
0 points   Incorrect responses, or no response provided.



Question 7 - Type of Reaction 1 point total

Criteria:
1 point   Correctly identifies this as a hydrolysis reaction.
0 points   Incorrect responses, or no response provided.


Question 8 - Explain Hydrolysis 1 point total

Criteria:
2 points   Correctly states that the lactose (disaccharide) is broken down into simpler molecules of glucose and galactose (monosaccharides) by the addition of a water molecule. Answer should be written in complete sentences.
1 point   Correct statement, but not in complete sentences.
0 points   Incorrect responses, or no response provided.

 


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