Stain specificity for mitochondria in living cells

Steps:

• Identify the stain as Janus Green B, which temporarily colors living cells blue.
• Note that the blue fades quickly in most structures due to metabolic activity or diffusion.
• Recognize that mitochondria retain the stain longer because of their role in cellular respiration.
• Match this property to the option that fits mitochondrial staining.

Why D is correct:

• Mitochondria stay blue with Janus Green B as it binds to their cytochrome oxidase enzyme, a key component in electron transport.

Why the others are wrong:

• A. Endoplasmic reticulum: Lacks specific binding sites for this stain, so color diffuses away.
• B. Golgi body: Involved in protein modification, not respiration, allowing rapid stain loss.
• C. Lysosome: Contains digestive enzymes that degrade the stain quickly.

Final answer: D