Teaching Unit Summary Title: Understanding Enzymes using a Forensic Hook Learning Objectives Learning Goals



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Teaching Unit Summary
Title: Understanding Enzymes using a Forensic Hook
Learning Objectives

Learning Goals

Students will learn binding specificity

Students will understand the role of inhibitors

Students will apply knowledge to novel situations


Learning Outcomes

Students will be able to predict reactions between given enzymes and of family of substrates.

Students will be able to predict the consequences of the addition of an inhibitor.

Students will be able to interpret (quantitative/qualitative) enzyme assay test results.

Students will be able to relate the theoretical understanding to real-life applications.
Target Audience

Introductory biology

Second semester general, organic & biochemistry

Second semester general chemistry

Sophomore level forensic science students
Brief Description of the teachable unit: We will start with a crime scene scenario and use it to introduce enzymes, inhibitors, and enzyme assay tests.


  1. Scenario

Students are presented with a forensic case study:
In 1968 a woman was found strangled to death in a NYC alley. During the autopsy, the medical examiner discovered extensive bruising around the lips and mouth, and several green fibers in her teeth and throat. Microscopical analysis revealed that the fibers were common in both composition (cotton) and color (green). A month later a suspect was apprehended. The investigators discovered a green handkerchief in the suspect’s van. The investigators are now interested in linking the handkerchief with the victim. What might you do to accomplish this?
Students are asked to identify the potential substance (saliva). They are further asked to identify how saliva is different from other body fluids,

  1. As a formative assessment, students are asked to select the component of saliva that is the most unique (salivary enzymes).

  2. The fact that the salivary enzymes == amylase, and that amylase breaks down starch, sugar, and other carbohydrate is introduced if the students did not do so during discussion.

  3. The affinity of amylase for starch (and not other compounds) is posited as a means for detecting the presence of saliva on the object from the case study.

Content: Use a colorimetric reaction to visualize the presence of an enzyme in a physiological fluid.


Hook
The Phadebas test is widely used in forensic science to identify physiological fluids that contain the enzyme alpha-amylase. To perform the test, a forensic analyst needs both a positive and negative control.
Student Activity & Assessment

Can anyone explain what a negative control is?


Make it.
Can anyone explain what a positive control is?
I need a volunteer.
The last test tube contains residues from the handkerchief and is referred to as the questioned sample.
The reaction works by combining sample with a few millimeters of water, and a single Phadebase tablet (tablets can be purchased from Phadebas.com). The tablet contains starch microspheres covalently bonded to a blue dye. The microsphere-blue dye complex is insoluble in water. In the presence of alpha-amylase (from saliva), enzymatic activity cleaves the starch microsphere from the blue dye, releasing the dye into solution, and turning the entire volume a dark blue color. In the absence of amylase, the Phadebas tablet remains as an insoluble precipitate that accumulates in the bottom of the test tube, leaving a clear water column above (centrifuging the vials will help to improve the clarity of the negative control).


If the positive and negative controls behave as expected, then the unknown or questioned sample can be interpreted by comparison to the knowns.
Assessment:
Can the students accurately predict what results would be expected for the positive and negative controls? Did the handkerchief presumptively contain residues of alpha-amylase (and therefore saliva)?



  1. Enzyme specificity

Context: Introduction to enzymes
Active Learning: On board and/or as handouts, students will have a model for enzyme activity. Students will be asked to describe what is going on in the diagrams, with call-outs from the class. As students present important aspects using chemical terms, the appropriate definitions in biochemistry will be given.

Once a simplistic lock-and-key understanding has been developed, the more accurate idea of induced fit will be introduced.


Directory: sites -> default -> files -> basic-page-supplementary-materials-files
files -> Cte: Sequencing Assignments Characteristics of Effective Writing Assignments
files -> American Pharmacists Association Academy of Student Pharmacists Chapter Achievement Awards Program Reporting Guidelines
files -> Student: Professor: Peter Dickens
files -> Dese model Curriculum
files -> Pre-Health Organizational Meeting
files -> Essay prompts for the most common central applications amcas american Medical College Application Service (MD)
files -> Alert today alive tomorrow
basic-page-supplementary-materials-files -> National Academies Northstar Institute for Undergraduate Education in Biology Teachable Unit Framework
basic-page-supplementary-materials-files -> Group 4 rEvolutionaries
basic-page-supplementary-materials-files -> Evidence for Hominin Evolution

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