For more than a century, biology has largely viewed cellular communication as a chemical process. This chemical view has been very helpful in describing a large number of cellular signaling pathways. However, modern cell biology increasingly reveals a deeper reality. Cells are not simply bags of chemicals. They are highly organized information-processing systems operating across many scales simultaneously. Within every cell, billions of molecules continuously exchange infor

When most people imagine a living cell, they picture a microscopic bag of organic materials. In fact, as described in prior posts, a cell is a vast, organized society whose members constantly communicate, cooperate, negotiate, compete, and adapt to changing conditions. At the center of this society lies a remarkable transportation system: an immense network of molecular tracks, scaffolds, motors, signaling complexes, organelles, and regulatory molecules that continuously exch

Dynein is a vastly more complex motor than kinesin. It walks along microtubules carrying vesicles, RNA granules, mitochondria, signaling complexes, and even large full chromosomes. It moves the entire cell nucleus during immune cell movement and manages the extraordinarily complex choreography of chromosome separation during cell division. It is a motor with awareness of what each situation requires. Dynein is enormous. Including its essential additional dynactin complex, i

Kinesin is an individual cellular motor made of just four protein chains that senses, navigates, makes decisions, and walks with two feet, step by step like a human. It picks up a variety of cargo, such as vesicles, mitochondria, molecular complexes, or messenger RNA and walks, one deliberate step at a time, along a highway of protein cables toward a precise destination. Walking upright on two legs is rare in nature—humans, ostriches, penguins, kangaroos, and a few others—e

Many of the cell’s most important functions occur through the actions of a huge, dynamic, complex scaffold that extends throughout the cell. It consists of tracks along which molecular motors walk and carry necessary cargo everywhere in the cell. This scaffold is not made like rigid, passive railroad tracks, but tracks that grow, shrink, and bend—precisely organized, but dynamic and instantly responsive. The tracks stretch from the cell's center outward like spokes, providing

Since DNA’s discovery, molecular biology had operated on reassuring assumptions: every protein folds into one precise, stable shape; shape determines its function; and shape is determined by a sequence of amino acids produced by a sequence of DNA letters. It was a clean idea. The holy grail of bioscience for decades was finding the shapes of proteins and the DNA codes that determine that shape. It is very difficult to determine the shapes of any protein from the sequence of a

Water is the medium that makes life possible. Water is so ordinary that we rarely think of it as doing anything. But inside a living cell, water is not a passive background—it is an active participant in nearly every molecular event and every cellular structure. The water molecule has a peculiar geometry. One oxygen atom pulls so strongly on two hydrogen atoms that it ends up slightly negative, while the two hydrogens are left slightly positive, which results in four partial

Most people picture molecules as rigid, locked-together structures — like tiny pieces of stone. But the molecules inside every living cell are something far more remarkable: they hold together loosely and temporarily on purpose. The strongest molecular bonds—called covalent bonds—share electrons so firmly that breaking them requires a serious chemical event. These strong bonds produce the stable structures of large molecules like DNA, RNA, lipids, and proteins. When the DNA/R

Alternative splicing of messenger RNA has been shown to be critical for the development of the human brain. The ability to make many new and complex proteins allowed the development of the enormous molecular complexity in different neurons and in different regions. For some reason, in evolution humans developed the ability to use alternative splicing much more than other species. This ability is most prominent in the brain. This post updates the most recent understanding of h