Free response · Unit 2 Beta

A model of an engulfed bacterium

Analyze Model or Visual Representation · 4 points

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The question

Name: ______________________   Date: ____________   A model of an engulfed bacterium (4 points)

Model

A model of an engulfed bacterium

The model shows part of an early host cell shortly after it took in a free-living bacterium. Labels 1 and 2 mark the two membranes around the bacterium.

Bacterium inside a host cellPart of a host cell, bounded by its plasma membrane, with a nucleus on the left and large 80 S ribosomes in its cytoplasm. On the right, a bacterium sits inside the host, surrounded by two membranes: membrane 1, the inner one directly around the bacterium, and membrane 2, the outer one. Inside the bacterium are a closed loop of DNA and small 70 S ribosomes.Host cell plasma membraneNucleushost ribosomes (80 S)loop of DNA70 S ribosomes12

  1. (a) According to the model, describe where membrane 2 came from. [1 point]

  2. (b) Explain how two features of the bacterium shown in the model are used today as evidence that mitochondria descend from bacteria. [1 point]

  3. (c) The model shows how mitochondria began. Describe how the model would need to be changed or extended to show the origin of chloroplasts in plant cells. [1 point]

  4. (d) Researchers grow descendants of a modern plant cell for many generations with a low dose of a drug that blocks 70 S ribosomes but not 80 S ribosomes. Predict the effect on the cells' mitochondria and justify your prediction using the model. [1 point]