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Difficulty: Very hardCell Structure and Function

An unidentified eukaryotic cell maintains high metabolic activity through aerobic respiration, yet it does not release oxygen when exposed to sunlight and carbon dioxide. Additionally, when the cell is placed in a hypotonic solution (pure water), it swells but structurally remains intact without bursting. Based on these findings, which specific organelle is definitively ABSENT from this cell, and what structure provides its osmotic protection?

  1. A
    Chloroplast; cell membrane
  2. Chloroplast; cell wallAnswer
  3. C
    Mitochondrion; cell wall
  4. D
    Mitochondrion; cell membrane

Answer

Chloroplast; cell wall
The correct answer identifies that the inability to produce oxygen from sunlight and carbon dioxide means the cell lacks chloroplasts. Furthermore, the cell's ability to survive in a hypotonic solution (pure water) without bursting indicates the presence of a rigid cell wall, which provides structural support against osmotic pressure.

Step-by-Step Solution

1
Analyze the metabolic clue regarding oxygen and sunlight.
The cell does not produce oxygen in sunlight, meaning it does not perform photosynthesis. Therefore, chloroplasts are absent.
Chloroplasts are responsible for converting light energy and carbon dioxide into glucose and oxygen.
2
Analyze the metabolic clue regarding respiration.
The cell uses aerobic respiration, which confirms the presence of mitochondria.
Mitochondria are the site of aerobic cellular respiration in eukaryotes.
3
Analyze the structural clue regarding the hypotonic solution.
The cell swells but does not burst in pure water, indicating the presence of a rigid outer boundary.
Animal cells (which only have a cell membrane) will swell and burst (lyse) in hypotonic solutions. Cells with a cell wall (like plant or fungal cells) will become turgid but remain intact.
4
Synthesize the findings to select the correct pair.
The absent organelle is the chloroplast, and the structure providing osmotic protection is the cell wall.
Combining the deductions from steps 1 and 3 directly matches one of the provided options.

Key Concept

The functional differentiation of cellular organelles and structural boundaries (cell wall vs. cell membrane) under varying environmental and metabolic conditions.
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Topics

Cell Structure and Function

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