Cell Structure and Organisation: Question 6
Syllabus 2.1
A biology teacher shows the class an animation of a single, sausage-shaped structure inside a cell. As the animation plays, a label explains that this structure is where most of the energy needed for the cell's activities is released, during aerobic respiration.
Which structure is being shown in the animation?
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Worked solution
Step 1: Recall the clue given in the stem
The stem describes a structure that is “where most of the energy needed for the cell’s activities is released, during aerobic respiration.” This is a description of a specific function, not just a general description of shape.
Step 2: Match the function to a structure
Mitochondria are the organelles where most of the reactions of aerobic respiration take place, releasing energy that the cell can use for processes such as movement, active transport and building new molecules. Almost every cell, whether plant, animal or bacterial in a simpler form, needs mitochondria (or equivalent respiration machinery) to survive.
Step 3: Confirm the shape detail
Mitochondria are often described and drawn as sausage-shaped or rod-shaped structures in cell diagrams, which matches the description in the stem.
Why the other options are wrong
- B (nucleus): the nucleus controls the cell’s activities and holds the genetic material, but it does not release energy from respiration.
- C (ribosome): ribosomes are the site of protein synthesis, not energy release.
- D (chloroplast): chloroplasts absorb light energy for photosynthesis; they do not release energy by respiration, and they are not present in animal or bacterial cells at all.
Final answer
The structure being shown is the mitochondrion, option A.