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Biological Molecules Classification Lesson - High School Biology

A common topic in high school biology students includes the major classes of biological molecules - carbohydrates, lipids, proteins, and nucleic acids. Introductory lessons often rely on direct instruction and wrote memorization. The lesson here provides students an opportunity to make their own observations, notice patterns, and justify their own classification systems based on evidence. This lesson design promotes deeper critical thinking practices and opportunity for students to experience technology used by professional scientists.

Objective

Students will construct a classification system of major biological molecules based on structure and chemical properties. Students will further develop their observational and reasoning skills.

Lesson Plan

The instructor will prepare materials and computers to access Proteopedia for students. As the lesson is implemented, the instructor will facilitate student-to-student dialogue and ask high-level questions as students create their own classification system of biological molecules based on observations of compounds in Jmol. Afterwards, students will compare their classification systems to those which have been accepted by the scientific community.

Preparation

The instructor will print color copies of each of the unidentified sample molecules, making one set of manipulatives per student group. Each group will also have chart paper on which to arrange the samples and create their classification system. A key to CPK coloring shall be provided to students. Computers or laptops will also be provided to students so that they may access the student page on Proteopedia. After the main activity, students will have access to their textbook and other resources. The instructor may assign work from the appropriate chapters of the textbook to students. Prior to the learning segment, students are expected to have a basic understanding of chemistry, including concepts such as bonding, atomic structure, polarity, and common functional groups.

Implementation

Students will gather into groups of no more than four and be presented with color copies of Molecules A-E. Students will use a dialogue protocol (such as Talking Sticks) to generate observations of the molecules presented. This marks an opportunity for students to discover the most common elements in biological molecules.

Students will be given color copies of Molecules F-P and access to the Proteopedia site. If possible, each student will have access to a computer so that each group can view several molecules simultaneously. Students will be provided with chart paper on which they will organize their classification system. As students work, the instructor will observe student dialogue and ask for the reasoning behind student decisions. It is important that the instructor does not make corrections at this point, but rather asks students to justify their decisions by presenting evidence.

Once students have committed to a classification system, they will create a name for their molecule groups, affix the molecules to the appropriate spot on their chart paper, and explicitly write out features that are common to each member of the group.

Closing Activities

Students will be given an opportunity to view other student classification systems and engage in questioning and feedback. Students will then modify their classification systems and make final changes. In closing, the instructor will conduct a group discussion focused on the similarities across classification systems in order to determine which features of the molecules are most important for classification purposes.

After completion of the learning segment, students may be assigned an appropriate article or chapter about the main biological molecules. As students read, the instructor will prompt students to compare the scientifically accepted classification system to their own, with a focus on finding new information they did not have during the main activity.

Assessment

It is important that readings or lectures on the main biological molecules happen at the end of the learning segment so that students focus on making observations and using evidence-based reasoning rather than getting the "correct" answer. Classification systems will not be graded on how well they match the scientifically accepted classification systems, but on how thoroughly students made use of evidence and reasoning.

After completion of the entire learning segment, it is recommended to conduct a progress check on student ability to identify biological molecules or parts of biological molecules based on their structure and function. Such formative assessments will be used to inform further instruction prior to summative evaluation.

Molecules Used in the Activity

Standards

Common science teaching standards such as the Next Generation Science Standards and the AP Biology Framework support the content and instructional strategies used in this learning segment.

Next Generation Science Standards

• Performance Expectation HS-LS1-6 ^[1]
• Disciplinary Core Idea LS1.C: Organization for Matter and Energy Flow in Organisms^[1]
• Practice 2: Developing and Using Models ^[2]
• Practice 6: Constructing Explanations^[2]
• Crosscutting Concept 1: Patterns^[3]
• Crosscutting Concept 6: Structure and Function ^[3]

AP® Biology Course Framework ^[4]

• Big Idea 2: Energetics
  • Learning Objective ENE-1.A
    • Essential Knowledge ENE-1.A.2
• Big Idea 3: Information Storage and Transmission
  • Learning Objective IST-1.A
    • Essential Knowledge IST-1.A.1
• Big Idea 4: Systems Interactions
  • Learning Objective SYI-1.A
    • Essential Knowledge SYI-1.A.1
  • Learning Objective SYI-1.B
    • Essential Knowledge SYI-1.B.2
  • Learning Objective SYI-1.C
    • Essential Knowledge SYI-1.C.1

References

1. ↑ ^{1.0 1.1} HS-LS1-6 From Molecules to Organisms: Structures and Processes | Next Generation Science Standards
2. ↑ ^{2.0 2.1} Appendix F |Next Generation Science Standards Practices
3. ↑ ^{3.0 3.1} Appendix G |Next Generation Science Standards Crosscutting Concepts
4. ↑ AP® Biology |Course and Exam Description