Biochemistry Laboratory: Protein Isolation Quiz

Study Notes

Objectives include isolating proteins, observing physical properties, and identifying specific proteins through color reactions.

Gluten is extracted from wheat flour, acting as an insoluble protein residue after starch removal.
Materials Used: 100g wheat flour, iodine solution, cheesecloth.
Procedure: Flour and water mixed to form dough; kneaded and washed to remove starch.
Observations: Sticky, elastic gluten remains post-washing; iodine solution turns blue/black in the presence of starch.
Theoretical Result: Successful washing indicates starch removal if iodine does not change color.
Rationale: Iodine forms a blue/black complex with starch; no color change indicates the presence of pure gluten.

Objective involves extracting proteins from soaked beans.
Materials Used: 1 cup soaked beans, acetic acid, cheesecloth.
Procedure: Ground beans mixed with water, filtered, and acetic acid added to precipitate proteins.
Observations: White or off-white precipitate appears post-acid addition.
Theoretical Result: Globulin proteins precipitate out with acid.
Rationale: Acetic acid reduces protein solubility, causing them to clump and form visible precipitates.

Aims to isolate albumin, a key protein in egg white.
Materials Used: Egg white, acetic acid, NaCl.
Procedure: Egg white separated, weighed, and treated with acetic acid and NaCl to precipitate albumin.
Observations: A white, gel-like substance forms, indicating albumin presence.
Theoretical Result: Albumin should precipitate as a white solid.
Color Change: No specific color change; visibility of albumin results from its solidification.
Rationale: NaCl stabilizes protein precipitates, while acetic acid induces clumping.

Objective focuses on isolating myoglobin from minced beef, highlighting its role in oxygen transport.
Materials Used: Minced beef, ammonium sulfate solution.
Procedure: Beef mixed with ammonium sulfate, then filtered, and centrifuged for purification.
Observations: A dark red liquid containing myoglobin is produced.
Theoretical Result: Myoglobin, an oxygen-carrying protein, gives muscle its red coloration.
Color Change: No significant color change noted; myoglobin is naturally red.
Rationale: Myoglobin binds oxygen, maintaining muscle’s color and solubility.