Cell Organelles

The nucleus (sky blue) is a membrane-bound organelle found in eukaryotic cells that contains most of the cellular DNA. The DNA (not pictured) contains the information to create thousands of different proteins and RNAs that allow the cell to function and respond to its environment. To start this process, a temporary copy of the DNA recipe, called messenger RNA, is made. Unlike DNA, this RNA copy can leave the nucleus and travel to other parts of the cell, where proteins are built. Nestled next to the nucleus are two small light blue structures called centrioles. The centrioles sit in the middle of the centrosome, the starting point for a vast network of cytoskeletal structures called microtubules. These microtubules help give the cell its shape, determine the location of different structures inside the cell, support cell division, and form a super-highway of transportation throughout the cell. 

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

The outer membrane of the nucleus extends into a series of sac-like folds to create another organelle called the Endoplasmic Reticulum (light pink). The Endoplasmic Reticulum (ER) is the kitchen of the cell where the information from the recipes found in DNA is translated into proteins. The ER is full of molecular building blocks to assemble many different proteins and lipids for use within the cell. These products are then transported in vesicles to the Golgi apparatus or to other locations throughout the cell. The cellular kitchen in the ER is supported with a cytoskeletal scaffold of microtubules (golden strands) that provide physical support and direct connection for transport to other locations around the cell. 

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

After the endoplasmic reticulum has completed the basic construction of proteins and lipids,  they are moved into the Golgi Apparatus, also called the Golgi Body or Complex (green); the sorting and shipping center of the cell. This organelle is located around the centrioles (blue) where microtubules give the organelle its shape and serve as a hub for transport of lipids and protein around or out of the cell. In the Golgi Apparatus, enzymes modify and finalize the proteins and lipids produced in the ER,  preparing them for transport to their unique destinations. Once a delivery is ready to ship, the Golgi Apparatus will bud off a small piece of membrane to create transport vesicles. Look closely at the animation and you will see many small vesicle buds forming all around the Golgi Apparatus.  Once a budding vesicle containing protein or lipids breaks free of the Golgi it becomes an endosome (a type of vesicle) and is  transported along the network of microtubules to its final destination within, or even outside, of the cell. The steady formation and traffic of endosomes ensures the proper maintenance of different organelles and allows the cell to quickly respond to changes in its internal or external environment.

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

The cytoskeleton is one of the heroes of cellular function, providing the structure and scaffold for all basic cellular functions. This vast network of microtubules (golden strands) and other supporting molecules (such as actin and intermediate filaments) determine the location and structure of the organelles allowing them to maintain their basic function. The cytoskeleton allows for vesicle transport all around the cell, functioning just as roads, rails and highways allow for transit in a small city. Unlike our roads, the cytoskeleton can quickly be reorganized and restructured to rapidly change the shape of the cell or the location of different organelles. The cytoskeleton allows the cells to dynamically respond to its environment by redirecting the movement of resources within and out of the cell.

Learn More: 

• The Cytoskeleton Scroll and Explore
• Cytoskeletal Highways
   

 Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

Cell functions, such as the creation and transport of proteins within the cell, all require energy to operate. The vast majority of cellular energy is stored in the form of Adenosine Triphosphate (ATP), a nucleotide packed with stored chemical energy. The mitochondria (red) are ATP producing factories. Mitochondria are found throughout the cell and use oxygen to efficiently break down carbohydrates (sugars) producing an ample supply of ATP for cellular functions. Notice how the Mitochondria are positioned near the Golgi Body, providing  an on-site source of ATP to power vesicle transport and other cellular processes. The mitochondria are also involved in controlling the process of apoptosis or programmed cell death, an essential part of every cell’s life. Each mitochondrion contains a small amount of DNA to create its own ribosomes and other proteins essential to the important responsibilities of the mitochondria. 

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

This confocal microscopy video reveals the dynamic nature of Mitochondria. We often use static models of the cell that capture a single snapshot in time preventing us from understanding the dynamic reality of cell structures and functions. This video illustrates the wandering nature of the mitochondria (blue) as they move around the cell, providing a steady supply of energy to the Endoplasmic Reticulum (orange). 

Video created by Andy Moore, HHMI's Janelia Research Campus

The cream-colored endosomes (small membrane-bound vesicles) leaving the Golgi Apparatus or coming into the cell through endocytosis at the plasma membrane (not shown). These endosomes are transported throughout the cell and this video reveals the large scale nature and complexity of this process. Each endosome is transporting proteins or lipids with a set destination, taking its cargo to different organelles or to the plasma membrane to be released from the cell. Like air conditioning in many automobiles, endosomes create a different internal environment than their surroundings to support and maintain their cargo during transportation. As endosomes move along their route they begin to age which affects their function and integrity, the cellular equivalent of a automobile overheating while sitting in a traffic jam. This aging process makes it essential that the endosomes deliver their cargo quickly and directly. Endosomes that don’t meet the timeline for delivery will be redirected for destruction in the lysosome.

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

Endosomes that don’t make their delivery deadlines, have been marked for recycling, or endosomes created through endocytosis will be directed to the lysosome (purple) to have their contents broken down and the base components recycled. Lysosomes are small membrane bound organelles filled with an acidic bath of enzymes ready to break down biomolecules like proteins and lipids into their component pieces. Endosomes are like delivery trucks bringing a steady supply of refuse to the recycling center of the lysosome. To make a delivery, an incoming endosome will fuse its membrane with the lysosome membrane releasing its contents into the interior of the lysosome for digestion. Lysosomes also accept endosomes carrying foreign invaders like viruses, bacteria, or even shipments of material captured by the plasma membrane from outside the cell. Once broken down, the component pieces of the biomolecules are redistributed to be recycled within the cell. This recycling process is an integral part of the larger cellular system. 

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

If knowledge is power then the plasma membrane (gray) is the most powerful structure of the cell. Knowledge in this case means information gained from the external environment or surrounding cells. Serving as a barrier between inside the cell and the larger environment; the plasma membrane is continually collecting and transmitting information in and out of the cell.  Signals from the plasma membrane can trigger rapid gene expression within the nucleus; setting off a cascading response through all of the organelles illustrated in this narrative. The plasma membrane is embedded with a menagerie of proteins that serve as sensory input, messengers, gate keepers, and pumps. These diverse molecules allow the cell to respond to a myriad of different changes in the environment, transport nutrients, remove wastes, and raise the alarm to fight off pathogens. The plasma membrane encases the complex chemical reactions, relationships, and interactions that are the foundation for much of the life on our planet.

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

Life at all scales is a dynamic dance of survival and adaptation. All organisms from single-celled protists to the largest marine mammals have the same challenges of responding to their surroundings to maintain an internal stasis within their cells. This struggle for existence explains the form and function of ecosystems, organisms, cells, and even atomic structures of molecules.  This final animation brings all of the structures from this narrative together. Towards the end of the video, The plasma membrane fades away to reveal the orchestra of organelles we just explored. Each organelle plays an essential role in the function of the cell, working together to maintain the great dance of life.  

Video created by the Cell Map Team and Igor Siwanowicz, HHMI's Janelia Research Campus

For suggestions on how to incorporate this journey into your teaching, see our “Implementation Suggestions.”