biochem lab

• Denaturation - is a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive.
• Certain reagents such as UREA and GUANIDINE HYDROCHLORIDE denature proteins by forming hydrogen bonds to the protein groups that are stronger than the hydrogen bonds formed between the groups.
• Detergents such as SODIUM DODECYL SULPHATE denature proteins by associating with the non-polar groups of protein, thus interfering with the normal hydrophobic interactions.
• Organic solvents such as ACETONE ALCOHOL denature proteins by disrupting hydrophobic interactions.
• HEAT increases molecular motion which can disrupt attractive forces.
• None of these agents break the PEPTIDE BONDS, so the primary structure of proteins remains intact when it is denatured.
• A denatured ENZYME ceases/stops its function.
• A denatured ANTIBODY no longer binds to its antigen.
• A denatured MILK PROTEINS losses its biological activity
• higher temperature denaturation occurs means it is called HEAT DENATURATION or THERMAL DENATURATION
• denaturation occurs at lower temperature, then it is called COLD DENATURATION
• Denaturation occurs when proteins are exposed to an extreme environment conditions such as

  high level of salt,

  higher level of acidity,

  higher temperature
• Physical agents:

  ·         Heat

  ·         Violent shaking or agitation

  ·         Hydrostatic pressure

  ·         UV radiation
• Chemical agents:

  ·         Acids and alkalis

  ·         Organic solvents

  ·         Salts of heavy metals

  ·         Chaotropic agents

  ·         Detergents

  ·         Altered pH
• During cooking, this stress causes denaturation which is typically as heat and ultimately proteins gets coagulated
• Most proteins can be denatured by heat, which affects the weak interactions in a protein (primarily hydrogen bonds) in a complex manner.
• As higher temperatures can cause irreversible denaturation of proteins, and when a cell is exposed to high temperatures, several types of molecular chaperones swing into action for this reason, these chaperones are also called heat-shock proteins (HSPs).
• VIOLENT SHAKING OR AGITATION -

  ·         We see this clearly in the whipping of egg whites.

  ·         The constant churning of milk or cream creates foam from various proteins which also causes denaturation of proteins.
• HYDROSTATIC PRESSURE - Proteins undergo dissociation and unfolding by pressure mostly because the final states are more hydrated, have fewer non-hydrated cavities and therefore, occupy smaller volumes.
• UV radiation - supplies kinetic energy to protein molecules, causing their atoms to vibrate more rapidly and disrupting the relatively weak hydrogen bonding and dispersion forces of protein molecules.
• Acids and bases - disrupt salt bridges held together by ionic charges.
• acid and alkalis - Double replacement reaction occurs where the positive and negative ions in the salt change partners with the positive and negative ions in the new acid or base added. This reaction occurs in the digestive system, when the acidic gastric juices cause the curdling (coagulating) of milk.
• Acidic protein denaturants include:

  ·         Acetic acid

  ·         Trichloroacetic acid 12% in water

  ·         Sulfosalicylic acid
• Proteins can also be denatured by using organic solvents such as

  ether,

  alcohol,

  acetone,

  diethyl
• organic solvent - This added alcohol disrupts the hydrogen bond between protein molecules and new hydrogen bonds are formed instead between the new alcohol molecule and the protein side chains.
• The heavy metal salts usually contain

  mercury

  lead

  silver

  titanium

  Cadmium
• silver nitrate - is used to prevent gonorrhea infections in the eyes of new born
• chaotropic agent - is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules.
• Detergents - are amphipathic in nature having both hydrophobic side and a hydrophilic side (When dissolves grease, it forms protective bubbles from the water by surrounding grease molecules with the hydrophobic side).
• Proteins - have hydrophobic and hydrophilic sides; the detergent is attracted to these and forces the protein apart.
• Carboxyl groups (aspartic acid, glutamic acid, the carboxy terminus)
• nitrogen groups (amines on lysine, guanidine of arginine, and imidazole in histidine, etc.)
• true - The native helical structure of protein is lost.
• False -The secondary structure of protein with peptide linkages are intact and not hydrolyzed during denaturation.
• true - Denatured protein loses its biological activity.
• false - Denatured protein becomes soluble in the solvent in which it was originally insoluble.
• true- Denaturation is associated with an increase in ionizable and sulfhydryl groups of protein. This is due to loss of hydrogen and disulfide bonds.
• true- The viscosity of denatured protein solution increases while its surface tension decreases.
• true -Denatured protein is more easily digested. This is due to increased exposure of peptide bonds to enzymes. Cooking causes protein denaturation and therefore, cooked food (protein) is more easily digested.
• The study of denaturation of proteins helps in the field of proteomics