How do scientists grow protein crystals? | 14-16 years

In this activity, students read and enact an interview with a protein chemist as a stimulus for applying their knowledge about growing crystals. Students then discuss issues arising from this in groups.

Learning objectives

Students will be able to explain:

• That proteins can form crystals.
• The conditions under which protein crystals grow.
• That crystal structures can be determined using X-ray crystallography.
• Why protein crystals are investigated.

Sequence of activities

Introduction

1. Introduce the topic using a picture of a protein molecule.
2. Tell the students that they are going to find out how proteins form crystals and what scientists do with these.

Interview

1. Organise students into groups of four, ensuring that each group includes a competent reader.
2. Give each student a copy of ‘The body beautiful: protein crystals’ worksheet and the ’Interview with a protein chemist’.
3. Invite two students to ‘enact’ the interview for the rest of the class. One person will be the interviewer, the other will be the scientist.
4. After the interview has been read, circulate and support as students:
   • Read the material for themselves.
   • Work on the questions, agreeing answers.
   • Elect a spokesperson to feedback answers to the class.

Allow about 30 minutes for students to answer the questions.

Plenary

In a plenary:

1. Select spokespersons to give their feedback.
2. Review answers from the groups.
3. Check for understanding that proteins are large molecules that can form crystals because of their regular structures.
4. Check for awareness of X-ray crystallography as a technique for studying crystal structures.
5. Ensure that students apply their knowledge from previous work on crystals.

Feedback

Collect in the worksheets. Give written feedback on the quality of answers, particularly the students’ ability to apply knowledge and their understanding of proteins as potentially crystalline substances.

Commentary

Through discussing the work of a real scientist, students can see that their classroom and laboratory activities have relevance to ‘real’ science. The group work mirrors that of scientists discussing how to approach solving a problem.

Discussion, and the judgements that the students make during the discussion, produces coherent and credible responses to the issues raised. Through listening to each other and evaluating points raised, students learn alternative, valid viewpoints and so add to their knowledge.

Teacher feedback will assess the extent to which students have been able to apply knowledge to this topic area.

Answers

From ‘The body beautiful: protein crystals’:

1. Protein crystals are grown in a drop suspended from the top of a small container using a supersaturated solution. Evaporation of water takes place gradually, allowing protein molecules to form crystals.
2. The protein molecules are of different sizes and shapes, making different sized crystals.
3. They are regular molecules that can be packed into lattices.
4. Amino acids.
5. High humidity, regulated cool temperatures and relatively high salt concentration.
6. and 7. Proteins have important roles in the body, eg as structural substances in skin and hair and in the blood as antibodies or hormones. Scientists want to know about our body systems and how they work, so they need protein molecules for their experiments.
8. She provides the proteins other scientists need for their experiments.