Amino acid: molecules that contain carbon, oxygen, hydrogen, and nitrogen. These are the building blocks of protein......more
DNA: deoxyribonucleic acid is the information "blue-print" of the cell. It is a nucleic acid and is made from building blocks called nucleotides. This genetic information is passed from parent to child... more
Molecule: a chemical structure that has two or more atoms held together by a chemical bond. Water is a molecule of two hydrogen atoms and one oxygen atom (H2O)... more
Protein: a type of molecule found in the cells of living things, made up of special building blocks called amino acids.
Proteins are essential for all living things to function. They are large molecules made up of long chains of amino acids. Depending on the types of amino acids they have, proteins fold in very specific ways. The way they fold controls what the proteins are able to do. Proteins help move other molecules, respond to signals, make reactions happen more quickly, and replicate DNA, among other things. However, if proteins lose their specific folded shape, they are not able to work properly.
Proteins require specific conditions to keep their shape. For example, most proteins in our bodies rely on us to keep a warm (but not hot) body temperature, stay hydrated, and take in enough of specific nutrients like salt. If our bodies aren’t able to maintain these conditions, some of our proteins may not function as well, or at all. Most organisms actually produce special proteins called “molecular chaperones” that help other proteins and molecules continue to work even if conditions are becoming difficult to tolerate.
When a protein is exposed to conditions too far outside of a range it can tolerate, that protein’s shape will come undone. This is called “denaturing” (basically, breaking) a protein. We denature proteins all the time when we cook food (think: eggs). In this activity, we will use common household products or processes to denature egg proteins in two main ways—by cooking them, and by exposing them to concentrated alcohol (ethanol). Do you think egg will look the same or different depending on how the proteins it holds are denatured?
Watch biologist Melissa Wilson Sayres as she shows you step-by-step how to break the proteins in egg whites.
Why does denatured egg white turn from clear to white? If more than one treatment denatured egg whites, do you think the treatments denatured the egg whites in the same way?
Let’s look at each of the treatments we used:
Think about the effects of the two different water treatments. Do you think the water itself was denaturing proteins? If not, what was? If so, what was having the larger effect between the water treatments?
Are there any other processes you know of that turn egg whites from clear to white? What is it and do you think the same processes are happening?
Name another condition besides heat and exposure to a bond disruptor (like alcohol) that could affect the ability of a protein to maintain its shape.
What other things change color when their proteins are denatured?
Why might a living organism want to keep their proteins from denaturing?
In this activity, why was it important to have egg whites that we did not cook or add alcohol to?
Additional images via Wikimedia Commons. Soft-boiled egg by H. Alexander Talbot.
Karla Moeller. (2018, May 29). Breaking Proteins. ASU - Ask A Biologist. Retrieved September 24, 2020 from https://askabiologist.asu.edu/fr/node/4561
Karla Moeller. "Breaking Proteins". ASU - Ask A Biologist. 29 May, 2018. https://askabiologist.asu.edu/fr/node/4561
Karla Moeller. "Breaking Proteins". ASU - Ask A Biologist. 29 May 2018. ASU - Ask A Biologist, Web. 24 Sep 2020. https://askabiologist.asu.edu/fr/node/4561
When an egg is cooked, the clear liquid surrounding the orange yolk becomes more solid and white. What causes this to happen?