70 Fun Facts About Cell

Who coined the term "cell" in 1665 after examining thin slices of cork under a microscope?

The little compartments in cork reminded him of the small rooms, or cells, that monks lived in. What he actually saw were the empty walls of dead plant cells.

In which 1665 book did the word "cell" first appear, describing pores in a sliver of cork?

The book was the first major work on microscopy and became a bestseller; Samuel Pepys stayed up until two in the morning reading it.

The word "cell" comes from the Latin cellula. What does it mean?

The same root gives us the prison cell and the monk's cell, which is exactly the image Hooke had in mind.

Roughly how many cells make up a typical adult human body?

The estimate is around 36 trillion for an adult male and 28 trillion for a female, and most of them are red blood cells.

About how many different cell types are there in the human body?

Neurons, hepatocytes, red blood cells and their relatives all trace back to a single fertilised egg.

Which botanist developed cell theory with Theodor Schwann in 1839?

Schleiden worked on plants and Schwann on animals; the story goes that they compared notes over dinner and realised the two kingdoms were built the same way.

Rudolf Virchow's 1855 tenet "Omnis cellula e cellula" translates as what?

The tenet killed off the idea of spontaneous generation at the cellular level and completed what is now called classical cell theory.

Which organelle is nicknamed the "powerhouse of the cell"?

It earns the name by using aerobic respiration to make ATP, and it comes with its own small genome inherited from the mother.

Philip Siekevitz popularised "powerhouse of the cell" in a 1957 article in which magazine?

The article carried the phrase as its title, and it has been on every biology worksheet since.

A mature red blood cell has no mitochondria at all. Roughly how many can a single liver cell contain?

The liver's energy demands are enormous, while a red blood cell only needs to carry hemoglobin and can get by on glycolysis alone.

Which of these has no nucleus when mature and is packed with hemoglobin?

Ejecting the nucleus frees up space for hemoglobin and gives the cell its flexible biconcave shape for squeezing through capillaries.

Approximately how many new erythrocytes does an adult human produce every second?

They are made in the bone marrow, and after their run of roughly four months they are recycled by the spleen and liver.

How long does a human erythrocyte typically circulate before it is retired?

The cell has no nucleus, so it cannot repair itself; wear and tear eventually gets it flagged for removal.

Which Delft draper first observed bacteria and sperm cells using tiny single-lens microscopes he made himself?

His best surviving lenses magnify about 275 times, better than the compound microscopes of his day, and he wrote some 560 letters describing what he saw.

What did the Dutch microscopist who first saw bacteria call the tiny swimming creatures?

He argued in a 1676 letter to the Royal Society that because they moved on their own they must be alive.

Which organelle builds proteins by translating the code carried by messenger RNA?

It is mostly made of RNA rather than protein, which is one reason many think RNA came before DNA in the history of life.

Which Romanian-American cell biologist first observed ribosomes in the mid-1950s?

For a while they were simply called Palade granules; he shared the 1974 Nobel Prize for mapping the cell's inner structure.

Prokaryotic ribosomes are 70S. What size are the ribosomes floating in a eukaryotic cell's cytosol?

The S stands for Svedberg units, a measure of how fast a particle settles in a centrifuge, which is why 40S and 60S subunits add up to 80S rather than 100S.

Which Belgian scientist discovered lysosomes and shared the 1974 Nobel in Medicine?

He found them almost by accident while chasing an enzyme that kept turning up in the wrong fraction of his centrifuged liver cells.

The digestive enzymes inside a lysosome work best at roughly what pH?

The acidity is a safety feature: if the enzymes leak into the neutral cytosol they mostly stop working instead of digesting the cell.

Which Italian physician identified the cell's protein-packaging 'apparatus' in 1898?

For decades some biologists insisted the structure was an artefact of his silver stain; the electron microscope finally proved it was real.

The stacked, flattened membrane disks that make up the cell's protein-dispatch organelle are called what?

They are sorted into cis, medial and trans compartments, so proteins move through the stack like parcels along a conveyor.

Which organelle carries out photosynthesis in plant and algal cells?

A wheat leaf cell can hold up to 100 of them, and each carries its own DNA left over from a captured cyanobacterium.

The green pigment in a plant cell is held in stacks of disk-like sacs called what?

A stack of them is a granum, and the fluid around the stacks, the stroma, is where sugar is actually assembled.

Lynn Margulis's 1967 paper argued that mitochondria and chloroplasts were once what?

The paper was rejected by more than a dozen journals before it was printed, and the endosymbiotic theory is now textbook orthodoxy.

Who coined the term "mitosis" in 1882, from the Greek word for a thread?

The threads were the chromosomes he watched condensing under his aniline dyes; the word chromatin is his too.

During which stage of mitosis do chromosomes line up along the middle of the cell?

The imaginary line they gather on is the metaphase plate; the checkpoint here makes sure every chromosome is attached before the cell pulls them apart.

What is the splitting of the cytoplasm into two daughter cells after nuclear division called?

Strictly speaking it is not a phase of mitosis at all; animal cells pinch in two with a contractile ring while plant cells build a new wall down the middle.

After both rounds of meiosis, how many haploid cells has a single starting cell produced?

In human females only one of the four becomes a usable egg; the other three shrivel into polar bodies.

Who first described meiosis in 1876, working with sea urchin eggs?

The word itself came later: J.B. Farmer and J.E.S. Moore introduced it in 1905, spelling it "maiosis".

The fluid mosaic model of the cell membrane was proposed in 1972 by S. J. Singer and which co-author?

The model pictures the membrane as a two-dimensional liquid in which proteins drift about like icebergs, replacing the older idea of a rigid protein sandwich.

A cell membrane is a double layer built mostly of which type of molecule?

Each has a water-loving head and two water-hating tails, so in water they line up tail-to-tail automatically.

Which cell line, taken from Henrietta Lacks in 1951, became the first immortal human cell line?

The cells doubled every 20 to 24 hours and simply refused to die; they have since travelled into space and been used in tens of thousands of studies.

The first immortal human cell line was mass-produced in the 1950s so that whose vaccine could be tested?

The National Foundation for Infantile Paralysis set up a production plant at Tuskegee Institute to grow enough of the cells.

What is the main job of the nucleolus?

It is not wrapped in a membrane; it is simply the dense region where the ribosomal RNA genes are being read at full speed.

Which Scottish botanist described the cell nucleus in detail in 1831?

He is the same Brown whose jittering pollen grains gave us Brownian motion.

Fungal cell walls are built mainly from which polymer?

It is the same tough material that makes up insect exoskeletons and crab shells.

Bacterial cell walls are made of which material, also called murein?

Penicillin works by sabotaging the cross-links in this mesh, which is why it harms bacteria but not our own wall-less cells.

Which human cell, about 120 micrometres across, is among the largest and visible without a microscope?

Karl Ernst von Baer discovered the mammalian version in 1827; a fertilised one is called a zygote.

Roughly how many neurons does the human brain contain?

The longest axon of a human motor neuron can run over a metre, from the base of the spine to the toes.

Which German anatomist introduced the term "neuron" in 1891?

He also coined "chromosome" three years earlier; naming things was something of a habit.

In 2006 Shinya Yamanaka's team showed adult tissue could be reprogrammed back into what?

Just four genes did the trick, and the resulting induced pluripotent stem cells earned him a Nobel Prize six years later.

About how many cells does an average adult human lose each day to apoptosis?

That is roughly a body's worth of cells every year, all quietly replaced.

The word "apoptosis" comes from the Greek for what?

The image is of leaves dropping from a tree; the term was chosen in a 1972 paper by Kerr, Wyllie and Currie.

Brenner, Horvitz and Sulston won the 2002 Nobel for identifying cell-death genes in which organism?

Caenorhabditis elegans has exactly 959 somatic cells as an adult, and researchers know the fate of every one of them.

Leonard Hayflick showed in 1961 that a normal human fetal cell population divides about how many times?

The finding refuted Alexis Carrel's long-standing claim that normal cells were immortal.

Which enzyme lets most cancer cells keep dividing past the Hayflick limit?

It rebuilds the protective caps on the ends of chromosomes that shorten a little with every division.

Prokaryotes keep their main genome in a region of the cytosol called what?

Extra genes often ride on separate circular plasmids, which is how antibiotic resistance hops between bacteria.

Which two domains of life are made up entirely of prokaryotes?

The distinction goes back to Edouard Chatton's writings in the 1930s, long before anyone had sequenced a gene.

In some mature plant cells the central vacuole can swell to occupy what share of the cell's volume?

The pressure it exerts, turgor, is what holds a non-woody plant upright; lose it and the plant wilts.

Which organelle stores calcium ions inside muscle fibres and releases them on a nerve signal?

When a nerve signal arrives it dumps the calcium into the fibre, which is the trigger for contraction.

Microtubules, the widest fibres of the cytoskeleton, are built from which protein?

They are about 25 nanometres across and double as the tracks that motor proteins haul cargo along.

Paul Boyer and John Walker's 1997 Chemistry Nobel was for explaining how cells make what?

An adult burns through roughly their own body weight of it every day, recycling each molecule hundreds of times.

In osmosis, solvent molecules cross a selectively permeable membrane toward a region of what?

The classic demonstration is a potato slice in salt water: water leaves the cells and the slice goes limp.

Which type of white blood cell makes up 60 to 70 percent of those circulating in the blood?

They are the first responders to infection and are the main ingredient of pus.

Who determined in 1956 that human cells contain 46 chromosomes?

For three decades before that, textbooks confidently taught the wrong number.

During which part of the cell cycle is the DNA replicated?

By the end of it every chromosome consists of two identical sister chromatids joined at the centromere.

What is the resting phase called in which a cell has left the cell cycle and stopped dividing?

Most neurons and heart muscle cells sit here for a lifetime, which is why damage to them is so hard to repair.

Hartwell, Hunt and Nurse won the 2001 Nobel for discovering the cell cycle's regulator molecules. What are they?

They pair up with cyclin-dependent kinases; the cyclin part rises and falls through the cycle like a tide.

The primary wall of a land plant is built mostly from which polysaccharide?

It is the most abundant organic polymer on Earth, and cotton fibre is close to pure cellulose.

Which of these groups of organisms has no cell walls at all?

Without a rigid wall, animal cells rely on the cytoskeleton and the extracellular matrix for shape and support, which is also what lets them crawl and change form.

Which giant bacterium, averaging 1 cm long, is the largest known and visible to the naked eye?

Most prokaryotes measure just 0.1 to 5 micrometres across.

The word 'eukaryote' derives from Greek meaning what?

The 'nut' refers to the membrane-bound nucleus that defines the group.

The magnetosome is a membrane-bound organelle unique to which kind of bacteria?

Anammox bacteria have their own unique organelle, the anammoxosome.

The single totipotent cell from which most distinct cell types arise is called what?

It differentiates into hundreds of cell types during development.

The bacterial capsule of Bacillus anthracis is made of what type of molecule?

Pneumococcal capsules are polysaccharide, and streptococci use hyaluronic acid.

Which genus of bacteria possesses only a cell membrane and no cell wall?

Most bacteria have a plasma membrane covered by a wall, sometimes with a gelatinous capsule on top.

Roughly how long ago did cells first emerge on Earth?

All organisms are grouped as either prokaryotes or eukaryotes.

Short attachment pili on bacteria, made of the antigenic protein pilin, are called what?

The longer conjugative pilus is the other main type.

Linear plasmids have been found in which spirochete genus, the cause of Lyme disease?

Most bacterial plasmids are circular and often carry antibiotic-resistance genes.