Membrane Permeability

AP Biology· difficulty 3/5

Beet root tissue contains red pigment in vacuoles. Cores were exposed to 30, 50, and 70 deg C water for 5 minutes, then absorbance of the surrounding water at 530 nm was measured.

Temperature (deg C) Absorbance 30 50 70

The trend is best explained by:

  • A

    Heat denatures the pigment, increasing absorbance.

  • B

    High temperature disrupts the lipid bilayer and proteins, increasing membrane permeability.

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  • C

    Beets actively transport pigment out at high temperatures.

  • D

    Pigment is synthesized faster at higher temperature.

Explanation

As temperature rises, phospholipid mobility increases and proteins denature, compromising membrane integrity. Pigment leaks out passively, increasing absorbance of the bath solution.

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