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Objective

SWBAT describe the process of protein denaturation and how it affects several types of proteins.

Big Idea

How do eggs and milk turn from a liquid to a solid when they are heated? Isn't it supposed to go the other way? Students learn the science behind this mystery as they denature proteins through the application of heat and chemicals.

Engage

5 minutes

When students enter the room, I hand them each a plastic egg, similar to the ones used at Easter time. Inside the eggs, I have placed terms that will be included in today's lesson:

  • denature
  • denaturation
  • amino acids
  • protein
  • albumin
  • casein
  • bonds
  • acid
  • heat
  • pressure
  • keratin

I have each student open their egg and read the term to their table partners and then discuss what they already know about any of these words. I also have them apply what they already know to guess what we might be learning about today.

Explore

20 minutes

After hearing some of the guesses made by my students, I explain that we will spend the new few days learning about proteins. I ask them to brainstorm a list of foods we eat that are considered proteins or are high in protein. After collecting a variety of answers and writing them on the board, I ask them to decide what most of these foods have in common, as well as which food group/s they mostly belong.

Next, I ask the students to use a technology device to look up images related to the structure of a protein.  After giving them a few minutes to search, I ask them what they have noticed. Most will realize that proteins look like spiraled, coiled masses of strings.  I confirm their observation and explain that in these foods known as proteins, a very interesting chemical reaction, called denaturation, can occur, which affects the spiraled structure they have observed.

I pass out the Denaturation Video Worksheet and explain to the students that will will learn about denaturation, including its causes and effects on certain types of foods. I have the students take notes on the worksheet as they read, repeating the Protein Denaturation video if necessary.

Explain

10 minutes

After watching the video, we discuss the worksheet questions together, making sure each student has a solid understanding of the denaturation process and how it affects proteins. Next, I have them conduct a simulation to further apply the concept to eggs, which contain a high amount of the protein, albumin.  I ask the students to write a $1 Summary of what they have learned from the video and the simulation.

 

Elaborate

15 minutes

Now that the students have gained an understanding of the denaturation process,  we complete the Denaturing Proteins Lab and compare our findings as a class.

I have the students investigate two different questions during a one-day lab:

  • Do all proteins denature at the same temperature?
  • What other methods will denature proteins?

 

On the second day, I provide them with a hands-on demonstration of how it actually works. Our visiting chefs (see reflection for more information) come to demonstrate how to cook the perfect egg, based on the concept of denaturation. The chefs review the concepts we studied and discuss how overcooking the eggs causes rubbery yolks, as a result of the proteins being over-bonded at too high of a temperature or for too long. They also allow each student to scramble or fry their own egg. We don't waste that food, students can eat their egg later.

Evaluate

10 minutes

As a final evaluation, I have the students complete the reflection activities following the lab. One of the questions I am particularly curious about is the last one regarding keratin (the protein found in hair, nails, and skin) and why someone would want to denature this protein.

Because students have been so focused on food, they assume keratin is food-related. This question forces them to change the direction of their thinking and apply what they have learned about denaturation in a completely different way.