It is quite interesting to think about how people perceive the living cell, whether they think of it as a blob, a little static ball, or something dynamic. Our cells are in reality a little bit of all these things, as well as a small but dedicated machine completing the function of keeping us alive. But within your cells, conditions are constantly changing, as proteins and whole organelles (parts or ‘organs’ of the cell) travel inside the cells using other proteins in the process of growth in animals or trying to get maximum sunlight in plants. Let’s dive into some cases of cell components moving to break the concept of cells being only static balls packed with proteins into constantly moving and ever-changing bustling communities inside of you.

The first instance of movement is in cell division, better known as mitosis. Part of this division involves copies of your DNA being pulled to opposite corners of the cell using spindle fibers, web-like protein strands made of proteins that resemble lego-bricks (tubulin) that can assemble to lengthen and disassemble, called microtubules. They emerge from an organelle called the centriole, which helps in organizing them. The centriole makes a copy of itself at an earlier stage in our DNA copying process, and the (now) two centrioles move off to opposite ends of the cell. These spindle fibers then emerge from the centriole like little webs or fingers, attaching to a protein at the center of your DNA’s little x cross form at the center of the cell from each end. This sort of has a similar effect to opening a packet of chips from both sides, which eventually gives way as the protein splits. The X shape of the DNA then turns into two little v shapes that get pulled back to the ends of the cell because the microtubules shorten. The cell then makes a split, pulling in on itself and creating a figure 8, then eventually breaking off into 2 cells (cytokinesis). Hence, even in making new versions of itself, our proteins and cell organelles are in (slow, but) constant movement.

Another example of movement within cells is in the simple action of you flexing your muscles, and even this has its own little story. The sliding filament model of muscle contraction, as it is called, shows the connection (literally) between the two proteins in sheets of muscle proteins within muscle cells, called myofilaments. These help conduct any movement in your body. If you slice your muscle the right way (don’t try this at home!), you can see loads of copies of two sheets of protein tubes, one of actin and the other of myosin (the two proteins), sandwiched together. Calcium ions flood into your muscle cells when you receive a sensory message to move your arm, for example, and these ions bind to two proteins that surround and cover the site where myosin attaches on actin. It causes them to change shape and move away, clearing this binding site. The myosin binds to the actin strand and pulls it when an energy giving molecule (ATP) breaks down. This causes the filament sheets to slide over each other, closing in and shortening the overall muscle strand. This action repeats itself, almost in a sliding fashion to help pull the long muscle sheets into themselves, and to contract your bicep upwards.

Other than in mechanical movement, whole organelles called chloroplasts in plant cells move around the cell to receive maximum sunlight for photosynthesis to occur smoothly. In our cells, we have a cytoskeleton, and this helps give the cell a structure. But unlike the human skeleton, the cytoskeleton allows for the cytoplasm (the thick jelly-like fluid in the cell) and organelles to move around the cell using proteins that hang onto and move along it like a tightrope. These proteins share similar names with the proteins from earlier, actin and myosin, but with different functions. Myosin carries the cytoplasm as a motor protein (the protein that walks along a protein strand in the cytoskeleton), and it carries the chloroplasts along in plants; while the actin here is the part of the rope-like filament that the myosin travels along. So in this case, there is a slower zip-line experience for cytoplasm rather than the sliding of sheets over one another (as was the case with the muscles). However this is still a useful motion that helps transport parts of cells around to get hold of more sunlight for making nutrients efficiently.

There are many other instances of the dynamic nature of cells. When you think about it, every movement you make requires the movement of cells. Despite their small size, the harmonious work of cells has a huge impact.