With a diameter of just under 700 pm (0.7 nm), francium is the largest known atom. The smallest atoms like hydrogen and helium are about one third of the diameter of francium, making the atomic size range relatively narrow. With a half—life of only 22 minutes, francium is extremely radioactive. (The diameter is calculated from the van der Waals radius.)
The transistor is the core unit of a computer’s brain — a binary switch that can be read either as O or a 1. Primitive transistors took up a lot of space and didn’t scale easily. Then in 1959 came the integrated circuit — the computer chip — which could house many transistors in a very small space. Now there was a way to scale the number of transistors in a computer, and Moore’s Law — the concept that the number of transistors that can fit onto a computer chip doubles every 18 months — was born. In 2020 we have transistors as small as 1 nm. But Moore’s Law is now hitting a wall as the transistors are getting close to atomic sizes. New technologies, like quantum computing, will be needed in order to maintain the exponential growth in computing power.
Adenosine triphosphote or ATP is probably the most important of all molecules: all known living things depend on it in order to get energy. Whenever you eat something, your body breaks down the glucose from the food and transports it into the cells, where it is then transformed into the ATP that your body needs for energy.
The human body is a busy machine with trillions of working parts that never take a break. It requires a lot of energy to keep going. Instead of plugging ourselves into an outlet or running on a battery, humans are more like cars that run on fuel. Glucose is human fuel: it’s a simple sugar that comes from the carbohydrates we eat. Once it enters our bloodstream, insulin is pumped into our blood to regulate the process of glucose entering our cells, while extra glucose gets stored in our muscles as glycogen. Too much glucose storage turns into excess fat.
DNA is the instruction booklet that tells your body how to turn food into you. There are a lot of instructions, so DNA is coiled super tightly and efficiently into the chromosomes in your cells — so tightly that there’s 2 m of DNA in each microscopic cell. There are an estimated 40 trillion cells in a human body, which means that if you stretched all of your DNA out into a single thread, it would be 57 billion km long. That’s long enough to wrap all the way around the Earth… l.9 million times.
Phospholipids are the building blocks of cell membranes. The spherical part — the phosphate head — loves water. while the two long things — fatty acid tails — are hydrophobic: they hate water. So two layers of phospholipids naturally bind together with the phosphate heads on the outside and the tails hiding from water on the inside. This two—layer system is a cell membrane, which is great at letting some particles through, while blocking others.
Ultraviolet light has wavelengths too small for our eyes to see. But it’s there, and it has all kinds of effects on us, like burning our skin and enriching our bodies with vitamin D. UV radiation makes up 12% of the Sun’s total radiation. That would be way too much for human bodies to handle, if most of it were not absorbed by the atmosphere before reaching the ground.
Among DNA viruses that infect mammals, circoviruses are the smallest we know of. Their single strand of genes is a true minimalist’s dream: it is solely designed to copy and package their DNA, nothing else.
Viruses are parasites, feeding on other organisms. Turns out that some of them have their own parasites: virophages, small viruses that rely on bigger viruses by invading their replication factories and hijacking them. Ironically this virus-stacking is often a blessing for the infected cell: the tiny virophages are much less of a burden on them than the bigger virus that got the boot.
No one likes the human immunodeficiency virus. When it infects humans, for example via sexual transmission, it damages vital cells in the immune system until the deterioration leaves the person with acquired immunodeficiency syndrome, aka AIDS.
Scientists believe HIV originated in chimpanzees in West Africa, making the jump to humans on a few occasions before exploding as a global pandemic in the 1980’s. HIV is one of the deadliest viruses to ever plague humans, but major medical breakthroughs since the ‘80s have allowed people with HIV today to live long, healthy lives.
Keishinrei