FOTE 2O2 Midterms Part 2

The Kjeldahl method measures protein content directly.

• True

• False

Answer explanation

• The Kjeldahl method measures nitrogen, which is then converted to protein content using a conversion factor.

Ammonium sulfate is commonly used in salting out because of its high water solubility.

• True

• False

Answer explanation

• Ammonium sulfate is commonly used in salting out due to its high solubility in water.

Dumas method is a newer, faster alternative to the Kjeldahl method, using high temperatures to release nitrogen.

• True

• False

Answer explanation

• The Dumas method requires high temperatures and is faster than the Kjeldahl method.

UV-visible spectroscopy techniques can analyze foods without extensive sample preparation.

• True

• False

Answer explanation

• UV-visible spectroscopy generally requires sample preparation to eliminate substances that might interfere with light absorption or scattering.

Ion-exchange chromatography separates proteins based on their size differences.

• True

• False

Answer explanation

• Ion-exchange chromatography separates proteins based on charge, not size.

In the Lowry method, cupric ions (Cu²⁺) react with peptide bonds under alkaline conditions.

• True

• False

Answer explanation

• In the Lowry method, the biuret reagent is used in combination with the Folin-Ciocalteau phenol reagent, which reacts with tyrosine and tryptophan residues to produce color.

Size exclusion chromatography uses porous beads to separate proteins based on charge.

• True

• False

Answer explanation

Size exclusion chromatography separates proteins based on size, not charge, using porous beads.

Turbidity is used to measure protein concentration in turbidimetric methods.

• True

• False

Answer explanation

• Turbidity is indeed used to determine protein concentration in turbidimetric methods.

In SDS-PAGE electrophoresis, proteins are separated by both size and shape.

• True

• False

Answer explanation

• In SDS-PAGE, proteins are separated primarily by molecular weight, as the SDS treatment standardizes the charge-to-mass ratio.

Isoelectric precipitation separates proteins by adjusting the pH to their isoelectric point.

• True

• False

Answer explanation

• Proteins precipitate at their isoelectric point, where they have no net charge.