A scientist wants to examine cross-sections of heart cell mitochondria to invest

Question

A scientist wants to examine cross-sections of heart cell mitochondria to investigate the number of the free ribosomes in the mitochondrial matrix. Which of the following preparations and instruments would be best for her to use?

Stain the specimen with dye and observe with a light microscope.

Coat the specimen with gold and observe with an SEM.

Fix the specimen with heavy metal atoms and observe with a TEM.

Observe the untreated mitochondria with a light microscope.

Stain the specimen with dye and observe with a light microscope.

Coat the specimen with gold and observe with an SEM.

Fix the specimen with heavy metal atoms and observe with a TEM.

Observe the untreated mitochondria with a light microscope.

Explanation / Answer

Ribosomes are very small and of the order 10-9 m so using a light microscope to observe them is out of the question(Light microscope can be used to view mitochondria but not the ribosomes in it).

An electron microscope should be used for this purpose, so it can be either the SEM(Scanning Electron Microscope) or TEM(Transmission Electron Microscope). The image in SEM is formed by the deflecting of electrons from the outer surface of the organelle unlike in TEM where the image is formed by the electrons transmitted through the specimen (a cross-section of mitochondria in our case).

So option (c) is the correct choice.

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