The Neurotransmission Cycle Revealed

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Objective

Students will use and develop protein models to construct explanations of receptor and enzyme specificity in the neurotransmission process.

Big Idea

Without the presence of specialized proteins in the synapse, neurotransmitters would be incapable of repeatedly producing or preventing action potentials.

Introduction

Lesson Background & Justification:

    Neurotransmission also referred to as Synaptic Transmission, is the process by which signaling molecules called neurotransmitters are released by a neuron (the presynaptic neuron), and bind to and activate the receptors of another neuron (the postsynaptic neuron). There are two forms of neurotransmission: chemical, or the processes induced by neurotransmitter release and mechanical or the physical induction of ions to generate and propagate an electrical current. Both processes contribute greatly to the emergent activities within tissues and thus, between cells. Similarly, these functions serve as an emergent activity of the molecular structures that drive them from a tier down: proteins. Proteins are large biological molecules, or macromolecules, consisting of one or more long chains of amino acid residues that perform a vast variety of functions in living systems. In this lesson, students will learn how to explain the basis of variety within protein structure and connect this to this molecule's contribution to neuron function. 

Prerequisite Knowledge: It is recommended that students be familiar with the structure and function of a neuron and the action potential mechanism. 

Lesson Preparations:

In the effort to prepare for this lesson, I make certain that I have the following items in place: 

a) A class set of MSOE Protein Folding Worksheet Instructions and Amino Acid Starter Kit Model Sets Purchase or Get on Loan (1 set per student groups of 2). 

b) Student lab books.

c) MSOE Synapse Modeling Kits- Soon Avaliable for Purchase

Common Core and NGSS Standards:

HS-LS1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

SP2- Developing and using models. 

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models. 

Standards Rationale:

      The power of DNA has been made very visible and comprehensible everywhere from court rooms to pop culture. Lacking therein is the understanding of DNA's products and why these unique structures are discriminatory.While it is important for students to comprehend to understand the nature of DNA, it is critical that they understand that proteins are the molecules that control life processes such as creating the unique structure of the neuron and how varying protein structures contribute to this cell's ability to execute communicative function.Thus, giving DNA credibility in the aforementioned situations. In this lesson, modeling is used to accomplish this task. 

      Modeling is the process by which scientists represent ideas about the natural world to each other, and then collaboratively make changes to these representations over time in response to new evidence and understandings. It is intimately connected to other scientific processes (asking questions, communicating information, etc.) and improves students ability to recall scientific jargon through association. In the classroom, it is important that teachers engage students in modeling practices, to set the foundation of success in a lesson or instructional unit. In this lesson modeling is used in concert with other science practices in the classroom to promote students’ reasoning and understanding of core science idea presented.

Engage

10 minutes

Section Primer: 

       A synapse is a separating space of about 12 nm high that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another cell (neural or otherwise). Within this space resides thousands of chemicals including a host of proteins for neurotransmission or for other neuron functions, though rarely characterized in images of synapses. Within this traffic of molecules resides the receptor proteins of the post-synaptic neuron. Once released, it is the job of the neurotransmitter to find and bind to this complimentary molecule. What essentially assures this process is the fit of the ligand or neurotransmitter to the corresponding receptor. In this section of the lesson, students use suggestive imagery from an animation to deduce that molecule fit (based on shape) contributes to the successful binding of the two molecules. This primes students to understand that there are other factors such as chemical compatibility of the ligand-receptor combination to accommodate this binding process and thus, facilitate processes such as neurotransmission. 

Section Sequence:

a) Slide 1: Read aloud and discuss the items on the screen with the entire class. Address each individually and wrap up the complete discussion by having students record their predictions of the final question presented. This is a time to simply hear student thoughts and potential misconceptions. 

* Note: The Goodsall image is hyperlinked to the words for viewing. 

b) Share with students that they will view a video clip that not only reminds us of what jobs certain neurotransmitters are responsible for, but how they manage to bind in all of the molecular traffic. Instruct them to look for these subtle clues in the imagery as they watch. Play the following:

c) Instruct students to revise and record their predictions based on the information presented in the clip and discuss student pre and post video ideas as a class.  

Standards Covered:

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models. 

Explore

30 minutes

Section Primer: 

       Proteins are large biological molecules, or macromolecules, consisting of one or more long chains of amino acid residues that perform a vast variety of functions in living systems based on their unique folding patterns. In this section of the lesson, students will learn how to identify a plethora protein structures and functions inside and outside of the neuron. They will use this information to first equate protein diversity to more versatility in functions within the same cell and later to use the model and the assignment to develop a diagram that integrates the molecule labeling with the steps of neurotransmission.

Section Sequence:

a) Slide 2: Share with students that the receptor molecules seen in the video are only a part of the neurotransmission equation. Like raising a child, it takes a community of unique proteins to make any biological event happen. Direct them to explore this concept by following the directions on the screen. Read the directions aloud and give students 20 minutes to complete the tasks. 

b) Discuss the final question of the instruction sheet as a class (emphasize diversity of form and function). Encourage students to use evidence from their modeling system and discussions with partners to justify their responses. 

Standards Covered:

HS-LS1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

SP2- Developing and using models. 

Explain

10 minutes

Section Sequence:

           In this section of the lesson, my goal is to give students the opportunity to translate their exploration experiences into a more molecular based explanation of neurotransmission using protein descriptions to explain how specific events occur. The idea is to get students comfortable with the idea of protein specificity so that they are prepared to explore this concept with greater depth in the subsequent section of the lesson. This activity proceeds as follows:

a) Slide 3: Share with the class that they will collectively explain neurotransmission by filling the boxes on the screen. Solicit a volunteer to start at the top, and to fill in one box only. After filling in the box, articulate to the class if this area describes a protein, if so to identify it and finally explain what it is specifically designed to do in the overall process of neurotransmission. Continue until the story is told by multiple students of the class.  

Note: The goal is to recap the major activities and concepts simulated in the modeling lab but using a different learning modality.  

Standards Covered:

HS-LS1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

SP2- Developing and using models. 

Extend

30 minutes

Section Primer: 

         Amino Acids are are biologically important organic compounds composed of amine and carboxylic acid functional groups, along with a side-chain specific to each amino acid. The side chains of these subunits become key to a protein's diversity and consequently its diversity of function once the amino acid units bond to form a polymer. In this section of the lesson, students elucidate the significance of these structures and how collectively, via distinct chemical interactions of these side chains, proteins can fold to form distinct shapes to perform a specific function such as the reception of a neurotransmitter. 

Section Sequence:

a) Slide 4: Share with students that they will now learn to explain why the proteins described in the previous image are designed specifically for the corresponding functions described. 

b) Read and direct students through the MSOE Protein Folding Exercise as prescribed by the directions on the screen. 

c) In the final discussion, make certain that students understand the emerging properties of the lesson from amino acid side chains to protein folds to protein diversity to neuron function.

Standards Covered:

HS-LS1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

SP2- Developing and using models. 

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models. 

Evaluate

15 minutes

Section Sequence:

           In this section of the lesson, my goal is to assess students understanding of the concepts presented through. The idea is to ascertain their comprehension of emerging properties from amino acid side chains to protein folds to protein diversity to neuron function. This activity proceeds as follows:

a) Slide 5: Distribute the Synaptic Transmission and Protein Evaluation sheets to all students. Review the expectations of the worksheet, give students 15 minutes to complete independently and collect as an exit ticket upon completion. 

Standards Covered:

HS-LS1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

SP2- Developing and using models. 

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models.