Protein Functions and Denaturation

Today we will continue the discussion from the last post about proteins. This post will be mainly focused on the functions of protein and denaturation.

Two Forms of Protein

 

The two forms of protein are globular and fibrous. Globular proteins are spherical. They are active during cell metabolism and consist of complex polypeptide chains. Globular proteins are soluble in water since their hydrophobic R groups are located in the core, away from the water molecules. Hemoglobin is aAn example of a globular protein, which has two alpha and two beta chains; hemoglobin conforms to the characteristics of a globular protein since they form complex proteins.

 

On the other hand, fibrous proteins are long and thread-like. They are insoluble in water since their hydrophobic R groups are exposed. Fibrous proteins are found in structural parts of organisms like tendons.

Functions of Protein

Listed below are six types of proteins and their functions.

Rubisco (globular): involved in the fixation of carbon dioxide from the atmosphere, providing a source of carbon

Insulin (globular): produced as a signal to absorb glucose and reduce the glucose concentration of the blood

Immunoglobulin (globular): Y-shaped proteins, or antibodies, involved in fighting infections by recognizing and binding to antigen molecules

Rhodopsin (globular): protein found on photoreceptor cells of the retina which allows low light intensities to be detected

Collagen (fibrous): structural protein found in muscles, ligaments, and tendons which prevents tearing in skin and fractures in bones

Spider silk (fibrous): produced by spiders to create webs

Denaturation

 

Denaturation refers to the structure change in a protein that results in the loss of its biological properties (BioNinja). Two main ways to denature proteins are to expose them to higher temperatures or to change the pH of the surroundings.

 

When a protein is exposed to high temperature, the high levels of thermal energy disrupt the hydrogen bonds, allowing the protein to unfold and lose its function. One crucial point is that the peptide bonds linking adjacent amino acids do not break. To prevent proteins from being denatured, the temperature of the surroundings must be the optimum temperature of that protein. The optimum temperatures vary depending on the type of protein, but most human proteins have an optimum temperature of 37 degrees Celcius, which is equivalent to body temperature.

Amino acids are influenced by the pH level since their charges alter due to the surrounding pH. Once the charge of a protein is changed, the solubility and shape of the protein will be modified, resulting in the loss of function. All proteins have an optimal pH in which it functions. For instance, the optimal pH of stomach proteins is acidic, while blood proteins have an optimal pH of neutral pH.

Works Cited

Allott, Andrew, and David Mindorff. Biology: Oxford IB Diploma Programme. Oxford University Press, 2014.

“Brent Cornell.” Denaturation | BioNinja, ib.bioninja.com.au/standard-level/topic-2-molecular-biology/24-proteins/proteome.html.