Lab: Building Proteins from Amino Acids

Teacher Preparation:

1. Review information found in the Background Agricultural Connections section of the lesson, lesson Procedures, and the attached Essential Files.
2. Assign one bead or bead combination to each amino acid. Students will need to be given the key prior to beginning their lab. You may choose to provide each student group with a visual key using the Amino Acid Color Chart. The chart lists each amino acid name and abbreviation. Place corresponding beads on each amino acid.
3. For each group, prepare four plastic bags containing a mixture series of “amino acids” for building each protein. Each bag should be labeled “Meat”, “Peanut”, “White Rice and Beans”, or “Toast” and contain 2 of each different colored “amino acids” (40 beads total) with the below exceptions:
   • Meat Amino Acids: No missing amino acid
   • Peanut Amino Acids: Missing Methionine and Tryptophan (replace both with clear beads)
   • Toast Amino Acids: Missing Lysine and Isoleucine (replace both with clear beads)
   • White Rice and Beans Amino Acids: No missing amino acid
     • NOTE: See student Materials list: 8 beads will be left over representing the limiting amino acids from toast and peanuts
     • Timesaver: Assign bead colors to each amino acid ahead of time. Consider using the supplemental Amino Acid Color Chart as a template by attaching (e.g. gluing) the beads directly to the chart. Provide one chart to each student group. Direct each group member to construct one protein molecule or assign students a strand to construct for homework.
     • TIP: If materials are not available, use the amino acid color chart (no colors) for the symbols. Copy the amino acid color chart as is for meat, and rice and beans. For peanuts, white-out the abbreviations Met and Trp and copy. For toast, white out Lys and Ile and copy. Students can then cut out the amino acid symbols and place them in the correct order. The amino acid symbols may be glued to another sheet of paper if desired.

Lab Procedures:

1. Distribute lab materials. It is recommended that materials are organized into stations for easier distribution. Students should be arranged in small groups of 4-5. Each group should receive the lab supplies outlined in the Materials section as well as 1 copy of The Building Blocks lab sheet and the Protein Connection handout.
2. Ask students to read Protein Connection and complete the focus questions for this lab investigation.
3. Launch the lab by asking students to predict which foods are considered complete proteins.
   • Timesaver: Instruct students to work individually within their groups. Each student can construct one of the four proteins to speed up the process.
4. Allow students to construct their protein models. Show students The Building Blocks lab demonstration video to show an example of how to construct a protein model.
5. Students should find two of the food sources (bag of beads) are missing one or two amino acids (colored bead).
6. Remind students to use a clear bead to represent any missing amino acid.
   • Meat: Animals proteins are complete.
   • Peanuts: Plant-based proteins are not complete, unless paired with another plant-based food that contains the missing amino acid. Legumes are missing the amino acids methionine and tryptophan.
   • Toast: Plant-based proteins are not complete. Grain sources are typically missing isoleucine and lysine. Lysine is particularly low in grain sources that have been exposed heated, such as toast.
   • White Rice and Beans: Plant-based proteins are not complete. Beans are typically missing methionine and tryptophan. On the other hand, grain sources are missing isoleucine and lysine. When the two are eaten together, the amino acids within each food combine to create a complete amino acid profile.
7. Allow students to work in small groups on The Building Blocks lab sheet to further explore the topic and respond to lab questions.
8. Consider allowing students to keep their protein strand. Students can wear the strand around their wrist like a bracelet and discuss what they learned about protein and sources of proteins with others.

Investigating Your Health Activity:

1. Instruct students to research various sources of lean protein prior to beginning the investigation.
2. Using the provided student background or information learned from researching protein sources, students should examine the food labels for three types of ground meat (i.e. 73% ground beef, 93% lean ground beef, and 93% lean ground turkey).
3. Students can find food labels in the grocery store, on USDA’s FoodData Central, or use the labels provided below.
4. If you choose to use the provided protein food labels, see the Teacher Key attached in the Essential Files portion of the lesson for answers to the Investigating Your Health lab questions. Answers to questions based on other food labels will vary.
5. If completed in-class, allow students to work in small groups on the handout to further explore the topic and respond to questions.
6. Follow-up with a class discussion about student findings related to the health benefits of consuming lean sources of protein.