Newswise — Hard labor might be the very thing we try to avoid on Labor Day. But our cells and their components don’t have the luxury of taking a day off. Their non-stop work is what keeps us going and healthy.
Scientists often compare cells with small factories. Just like a factory, a cell contains specialized compartments and machines—including organelles and other structures—that each play their own roles in getting the job done. In the vignettes below, we at NIH's National Institute of General Medical Sciences give a shout out to some of these tireless cellular workers.
Energy Generators
Mitochondria are the cell’s power plants. They convert energy from food into a molecule called ATP that fuels virtually every process in the cell. As shown here, mitochondria (brown) often have distinct, oblong shapes. Like most other organelles, mitochondria are encased in an outer membrane. But they also have an inner membrane that folds many times, increasing the area available for energy production. In addition, mitochondria store calcium ions, help make hemoglobin—the vital iron-containing protein that allows red blood cells to carry oxygen—and even take part in producing some hormones. Defects in mitochondria can lead to a host of rare but often incurable diseases that range from mild to devastating. Researchers are studying mitochondria to better understand their manifold jobs in the cell and to find treatments for mitochondrial diseases.
Protein Producers
Ribosomes are complex machines made up of more than 50 proteins and three or four strands of genetic material called ribosomal RNA (rRNA). The busy cellular machines make proteins, which are critical to almost every structure and function in the cell. To do so, they read protein-building instructions, which come as strands of messenger RNA. Ribosomes are found in all forms of cellular life—people, plants, animals, even bacteria. This illustration of a bacterial ribosome was produced using detailed information about the position of every atom in the complex. Several antibiotic medicines work by disrupting bacterial ribosomes but leaving human ribosomes alone. Scientists are carefully comparing human and bacterial ribosomes to spot differences between the two. Structures that are present only in the bacterial version could serve as targets for new antibiotic medications.
Assembly-Line Worker
The most obvious feature in many cells is the nucleus. Within the nucleus is a tiny structure called a nucleolus, which has the key job of constructing the rRNA for ribosomes. Ever poised and ready to chip in on a busy assembly line, the nucleolus positions itself on a section of DNA within a chromosome that has the instructions for making rRNA. The rRNAs pass through distinct areas in the nucleolus as they’re processed. Recent research has shown that the nucleolus’ compartments spontaneously self-organize to form this organelle because proteins that make up the nucleolus are like oil and water—they stay separate, creating distinct areas (blue, lime and red in the image) needed for proper function. Researchers study the nucleolus because, besides making ribosomes, it also checks the levels of proteins that control a cell’s growth. In some diseases, like cancer and heart disease, nucleoli are malfunctioning and lead to abnormal cell growth. Scientists are trying to find the causes of these aberrations and design treatments that restore normal nucleolus function.
For more examples of hard-working cell parts, see https://biobeat.nigms.nih.gov/2016/09/a-labor-day-themed-collection-hard-working-cell-structures
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