Topic: Proteins - structure

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Elementary school. Chemistry.

X. Chemical substances of biological importance. Student:

5) lists the elements whose atoms are part of protein molecules; defines proteins as compounds arising as a result of condensation of amino acids.

General aim of education

The student discusses the structure of proteins.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to characterize the binding occurring in the structure of proteins;

• to discuss the elemental composition of the peptide bond;

• to draw a structural formula for the peptide bond;

• to discuss the construction of proteins.

Methods/techniques

• expository

  • talk.

• activating

  • discussion;

  • mind map.

• exposing

  • film.

• programmed

  • with computer.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• interactive whiteboard, tablets/computers;

• sets for building particle models.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

Realization

1. The teacher, referring to the previous lesson, asks students what elements are included in the structure of proteins.

2. The teacher presents an interactive illustration showing the reaction scheme of joining two molecules of glycine and resembles the mechanism of amino acid joining.

3. Students choose groups of four. The teacher gives models to the molecules to the proteges and asks them to build a model of the dipeptide corresponding to the pattern displayed on the interactive whiteboard. After the expiration of the time, he checks the correctness of the task.

4. The teacher plays the presentation „The formation of a dipeptide in the reaction of glycine with alanine”. After the projection, the students, working in the same groups, arrange on the models for building molecules the equation of the reaction of condensation of glycine with alanine. After completion of activities, group leaders present the results of team work.

5. The lecturer presents an illustration of the general pattern of the protein chain. Students based on a fragment of the protein chain define the concept of proteins.

6. Students, working in pairs, analyze the illustration presenting different ways of presenting proteins. The indicated pair presents their observations.

7. The students carry out interactive exercise. The teacher initiates a discussion during which the correct solution is discussed.

Summary

1. The teacher briefly presents the most important issues discussed in class. He answers the additional questions of the proteges and explains all their doubts.

Homework

1. Develop a map of concepts containing issues learned during the lesson and bring your work to the next class.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Proteins - structure

Proteins are macromolecular compounds constructed from amino acid residues. The variety of proteins is huge, although protein amino acids only number around twenty. It is important which amino acids are included in the protein and how they are combined with each other.

Amino acids can be joined by a peptide bond. Remind yourself of how to combine two molecules of the amino acid into the simplest construction – glycine.

Proteins are conventionally called compounds whose chain contains more than 100 amino acid residues, and shorter chain compounds are included in the polypeptides.

The protein chain can be described by the general formula:

Protein chains may have a different spatial structure, e.g. they twist in spirals or ribbons.

Biochemists often refer to distinct aspects of a protein's structure:

Primary structure: the amino acid sequence. A protein is a polyamide.

Secondary structure: regularly repeating local structures stabilized by hydrogen bonds. The most common examples are the α‑helix, β‑sheet and turns. Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.

Tertiary structure: the overall shape of a single protein molecule; the spatial relationship of the secondary structures to one another. Tertiary structure is generally stabilized by nonlocal interactions, most commonly the formation of a hydrophobic core, but also through salt bridges, hydrogen bonds, disulfide bonds, and even posttranslational modifications. The tertiary structure is what controls the basic function of the protein.

Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word „proteinogenic” means „protein creating”. Throughout known life, there are 22 genetically encoded (proteinogenic) amino acids, 20 in the standard genetic code and an additional 2 that can be incorporated by special translation mechanisms.

• The molecules of all proteins are mainly composed of atoms of four elements: carbon, hydrogen, oxygen and nitrogen. Some of the proteins may include sulfur atoms, phosphorus and other elements.

• The basic elements building proteins are amino acids.

• Proteins are macromolecular chemical compounds, made up of amino acid residues joined by peptide bonds.

• Proteins are the main building blocks of organisms. They perform functions: building, transport, regulating and others.

• The source of animal protein include eggs, dairy, meat, fish, and vegetable – cereals and legumes, such as beans, soy and lentils.