As Good as Gold

What am I looking at?

This image shows a culture dish with cells from a cow that are fluorescently labeled for three different cellular structures. The nuclei are blue (1), the mitochondria are gold (2), and the actin protein within the cytoskeleton is gray (3). If you look closely, you can see that one of the cells was undergoing the process of cell division when this image was created (4).

Biology in the background

Mitochondria generate energy for cells through a process called the Krebs cycle. The Krebs cycle turns compounds derived from carbohydrates that are ingested – by cows and human alike – into energy-rich molecules that other cellular processes can use for fuel. This energy is usually stored for the short term within a molecule called adenosine triphosphate (ATP).

In all eukaryotes except plants and algae, the mitochondria are the only organelles with their own DNA – other than the nucleus, which contains most of the DNA in a cell. During reproduction, offspring receive half of their nuclear DNA from their mother and half from their father. However, offspring inherit their mitochondria from the mother, so all mitochondrial DNA is inherited from the mother and none from the father. According to endosymbiotic theory, mitochondria were once free-living bacteria that were engulfed by early eukaryotic cells. They have their own DNA and transcription/translation machinery, like that of other bacteria, although most of their genes were “transferred” to the host cell’s nucleus.

Mitochondria can vary in size, but the largest they grow is about 10 micrometers across, or roughly 7.5 times smaller than the width of a human hair.

Technique

This image was created using confocal microscopy.