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RELEVANT LEARNING OUTCOME:
(l) explain the effects of temperature and pH on protein structure
🕐Estimated time for this section: 10 minutes
Denaturation of protein
Denaturation of protein
Denaturation of protein is the loss of the specific 3-dimensional due to the disruption of chemical bonds that maintain the structure and thereby becoming biological inactive.
📑Read the lecture notes and learn to describe the process in detail by asking yourself these questions:
How does the structure of protein change during the process?
What are the chemical bonds affected during denaturation?
Protein Structure & Denaturation
Protein Structure & Denaturation
👁️🗨️Watch the animation to understand how upon denaturation, the unfolded protein aggregates into large and random structure.
During denaturation,
What happens to the hydrophobic region of one polypeptide chain after unfolding?
What happens to the peptide bonds of these unfolded polypeptide chains?
How does unfolded polypeptide chains aggregate into large insoluble random structure?
Effect of pH on the structure of protein
Effect of pH on the structure of protein
📑Read the lecture notes to find out how change in pH would affect the structure of proteins.
What are the chemical bonds affected when there is a change in pH?
What do you mean by optimum pH?
Why do proteins function best at optimum pH?
Effect of temperature on the structure of protein
Effect of temperature on the structure of protein
📑Read the lecture notes to find out what happens to protein structure when temperature is higher than its optimum.
📑Read the lecture notes to find out what happens to protein structure when temperature is higher than its optimum.
What are the bonds affected when protein is heated beyond optimum temperature?
How do unfolded proteins cause aggregation? (You may refer to the diagram below.)
🖊️Check Your Understanding: Conceptual Check
🖊️Check Your Understanding: Conceptual Check
Describe the factors that can lead to denaturation of protein. [7 marks]
pH
Change in pH alters the concentration of H+ in the medium, which alter the charges of acid and basic R groups of amino acids.
A change in pH may cause hydrogen bonds and ionic bonds between the R-groups to break.
This causes polypeptide chain to unfold and disrupt the specific 3D conformation and tertiary structure of the protein, resulting in denaturation.
Temperature
At temperature higher than the optimum temperature, kinetic energy of the molecules increases, leading to breaking of weak bonds.
Weak bonds such as ionic bond, hydrogen bond and hydrophobic interaction that maintain the protein structure break.
Polypeptide chain unfolds and disrupt the specific 3-dimesional shape of the protein, resulting in denaturation.
Other factors
Transfer of protein from an aqueous environment to an organic solvent causes the polypeptide chain to unfold;
In the presence of heavy metal, the positively charged ions/cations of heavy metals form strong bonds with the negatively charged carboxyl groups (-COOH) on the R groups of proteins and disrupt ionic bonds.
They also reduce the protein’s overall charge and increase its insolubility.
This causes the protein to precipitate out of solution.
Reducing agent is able to break strong disulphide bond.
🕹️Labster Simulation
🕹️Labster Simulation
Check in with your teacher for the following simulation.
Labster: Protein Denaturation Lab
In the Protein Denaturation lab, you will learn the different ways to denature proteins and their relation to food science. You will perform various experiments using ovalbumin, the primary protein found in eggs, in order to understand the chemical and physical causes of protein denaturation, and how it affects food texture. Will you be able to unravel the mysteries of cooking an egg?
User: mi.biologyh1h2@gmail.com
password: @MIsci1234
🖊️Check Your Understanding: Learning Goals Checkpoint
🖊️Check Your Understanding: Learning Goals Checkpoint
Attempt Qn 33 and 36 of the Proteins Learning Goals
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