Denaturation of Protein




Introduction: Denaturation of Protein

Simple way to explain the denaturation of protein and the buffer system in the blood.

(This experiment is for children from the 4th to the 6th standard)

I am currently majoring in biology in college and at times I take science/biology classes for children in the sixth standard. I have observed that a lot of teachers take classes in the same way whether it is for a child of 10 or a college level student of 20, they just bog them down with theories and concepts. At the age of 20, it is easy to grasp theoretical ideas and play around with them until you get comfortable with them but for children it is not as easy because their minds are not as open to abstract theories. Children take longer to get used to a dry theory but they are more observant and perceptive than adults, so why should the teacher not make the most of that gift? He can easily do this by using more graphic or visual demonstrations to prove a theory or a concept. Thus I believe that for children, education should be more practical and pertinent to life. To to demonstrate a theory, you can simply do experiments with things that you do in daily life.. Not only will they be more fascinated by the visuals but it is also a proof to them, that science is all around us and not just restricted to the lab.

I wanted to teach my class the importance of the pH of our blood and how it acts as a buffer. For that, I could have drawn a pH chart and simply shown them a number but what is the fun in that? It is merely a number that they are mostly going to forget by lunchtime. Thus I chose another medium with which I could demonstrate this concept more visually and using everyday things. The denaturation of the protein in milk.

This might sound complicated to a child but it is nothing else but the curdling of milk! If you have a carton of milk, a lemon and some pH strips then all you need now is your student’s attention. This experiment works perfectly to show a parallel between the denaturation of the protein in the body and the one in milk.

Through this Instructables, you should be able to teach your students about:

1. What is pH

2. The importance of pH balance

3. The buffer system of the blood

4. As a bonus- the composition of milk

This Instructables is divided into three easy experiments.

1. The curdling of milk

2. The coagulation of an egg white

3. The curdling of blood

And finally, please don’t forget to drop a vote in if you liked this project. Feel free to leave any questions in the comment section below. Happy teaching :)


The things you will need for all 3 experiments are:

1. 500ml of milk

2. 1 and half tbsp lemon juice

3. 5 pH strips

4. 1 egg white

5. 1 and half tbsp. of lemon juice

6. 1 petridish

7. 2 pipettes

Step 1: Contents of Milk

You can start the class by asking them ‘’who loves milk?’ a guaranteed number of students will wave their hands in the air. You can then slip in the question ‘what does milk contain?’ Give them a chance to brainstorm, if they do not get close to the contents then do not give the answers away! Give their minds a chance to exercise. But you can guide them to the answers which is that there are five ingredients that constitute milk- 86.5% water, 4.8% lactose, 4.5% fat, 3.5% protein and 0.7% vitamins and minerals. For your class, protein is the essential answer. Now you can start your first experiment.

For your first experiment the things you will need are:

1. 500ml of milk

2. 1 and half tbsp lemon juice

3. PH strip

That’s all and you are ready to go!

Step 2: Curdling of Milk

Now it is time for the first experiment.
Start by boiling the milk and wait until it begins to rise. Just at the moment of rising, add the lemon juice and stir continuously. Immediately the milk will curdle and separate into whey water and cottage cheese. Give three pH strips to three children and ask them each to dip it respectively into milk, whey water and lemon juice. You can then place the strips one next to the other and beside a pH chart for reference. Ask your students to answer the pH of each liquid.

Now it is when you ask them what is pH and why do different liquids react differently on a piece of paper?

Step 3: PH Chart

Now you can now show them this pH chart.

Through this chart you should be able to teach them that the pH value is a number from 0-14 with 7 as the middle (neutral) point. All the number below 7 indicate that a substance is acidic, 1 being the most acidic; you can point out to the vinegar and lemon on the chart as an example. And all the numbers above 7 are alkaline/basic, 14 being the most alkaline; you can refer to the chart for an example. Now that they are introduced to the idea of pH you can show them another example with the second experiment.

Step 4: Coagulation of Egg White

For this experiment, you will need

1. 1 egg white

2. 1 and half tbsp. of lemon juice

Just mix the two together and let it sit for roughly 15 minutes.

After 15 minutes the protein in the egg will begin to coagulate. This is your second proof that when you add something acidic to an alkaline base, there is a reaction. In these two cases there has been a direct effect on the protein.

Step 5: Protein in Muscle

Now to bring the student’s attention to our body and pH, you can show them this human anatomy of the muscle in the body.

The human body is made up of about 700 muscles that make up roughly half of a person’s body-weight. Muscles are primarily made up of protein thus you can now ask your students “as we are made up of so much protein, does that imply that when we consume something acidic our protein which in our case are muscles, denature?” to help them out, you can ask them how many of them have eaten oranges or drunk lemonade, a guaranteed majority would have; thus you can prove to them that though they eat acidic substances, their muscles remain the same and don’t curdle like in the case of milk.

Step 6: PH of Blood

Now it is time for the third and last experiment-
the curdling of blood.

For this experiment you will need:

1. Blood

2. Citric acid

3. pH strips

You can start this experiment by checking the pH of blood. On the pH strip it might show close to 6 but the actual blood pH is between 7.35 and 7.45 (any value higher than 7.8 or lower than 6.8 can lead to death. Below 7.35 would be mean that your blood is becoming too acidic and above 7.45 would imply that it is becoming too alkaline). This seems like a fairly narrow range so how does the blood or body put up with acidic molecules or basic molecules entering our blood? We must thank our blood for that, as it acts as a buffer to keep a homeostasis in the pH.

Step 7: Blood As a Buffer

You can take the time to explain the concept of a buffer.

A buffer is an aqueous solution that resists changes in pH upon the addition of an acid or a base. It is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid, a ratio of 1:10. A buffer can resist changes in pH when small volumes of strong acids or bases are added. When a strong base is added, the acid present in the buffer neutralizes the hydroxide ions; when a strong acid is added the base present in the buffer neutralises the hydronium ions.

To help them visualise this, you can give the analogy of an instance of tug of war. Suppose there are two teams and they are equally strong. If they pull from either side, the rope will not move as both teams are pulling with the same amount of force. In the same way, the base and the acid are tugging at each end to keep the liquid at a neutral state.

Step 8: The Importance of PH in Our Blood

Take the time to explain the importance of the blood being a buffer and the marvel of our body functions.

If the blood was not a buffer, the pH of the blood would go out of that small range of 7.35 and 7.45 and that is very dangerous! The enzymes in our body which help produce and speed up chemical reactions are very choosy about their environments. They function optimally at the right temperature and at the right pH. Thus if the pH in our blood could easily go out of range, the enzymes would stop working and sometimes they could even get permanently denatured. The malfunction of enzymes in turn affects the biological processes in the human body, leading first to diseases then eventually to death.

Step 9: Coagulation of Blood

So does that mean that our blood is invincible and can never curdle? No it is not, because it does curdle when there is an excess of acid and even the buffer cannot handle it.This is a rare and life-threatening situation.

To demonstrate the curdling of blood you can add 2 drops of citric acid to one drop of blood.

There is an immediate reaction- the protein in the blood begins to coagulate.

You can check the pH of this combination with a pH strip which shows that it turns acidic.

Step 10: Conclusion

It is time to conclude your class by explaining what causes the blood to become more acidic. When the blood drops below 7.35, it is known as acidosis. there are two kinds of acidosis- respiratory and metabolic. The former occurs when there is too much CO2 in the body and the latter occurs when the kidneys or lungs cannot eliminate enough acid or they get rid of too much base. There are a few factors that can contribute to the risk of having this- a high fat diet, kidney failure, obesity, dehydration and diabetes, most of this factors are controllable and are a choice of lifestyle. You can dismiss the class by putting this idea forth, allowing them to ponder over it- Though our bodies put up with our behaviours , one must not take it for granted; rather than abusing it we should treat it with care.

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    Question 3 years ago

    What type of blood is used for this activity?


    3 years ago

    A simple and easy way to demonstrate denaturation of protein and a very good way of introducing the concept of pH!


    3 years ago

    Looks like a great middle or high school science lab activity that students would find really interesting. Thanks for sharing!