KnowSoda
ScienceBiology
Cells: fun facts and quiz
The essentials in 7 ideas, with fun facts, an illustrated story and a quiz to see how much you know.
The essentials
What Cells Are
Cells are the building blocks of life. Some living things are a single cell; you’re made of roughly 30 trillion.
Key fact
Robert Hooke named “cells” in 1665 after looking at cork.
Inside a Cell
Most cells have a membrane around them, jelly-like cytoplasm inside, and a nucleus holding the DNA. Mitochondria release energy from food.
Key fact
Mitochondria are often called the powerhouses of the cell.
Plant & Animal Cells
Plant cells have a stiff cell wall and chloroplasts for photosynthesis. Animal cells have neither, which lets them change shape.
Key fact
Chloroplasts are what make leaves green.
Seeing Cells
Most cells are too small to see without a microscope. In the 1670s, Antonie van Leeuwenhoek became the first to see bacteria, which he called “animalcules”.
Key fact
A human hair is about ten red blood cells wide.
Cell Division
Cells multiply by splitting in two. Your body makes millions of new cells every second to replace worn-out ones.
Key fact
A fertilised egg divides again and again to build a whole body.
Bacteria
Bacteria are single cells with no nucleus. Most are harmless or helpful; your gut holds trillions that help digest food.
Key fact
You carry about as many bacterial cells as human cells.
Stem Cells
Stem cells can turn into many types of cell, like muscle, blood or nerve. Doctors use them in treatments such as bone marrow transplants.
Key fact
Bone marrow transplants have used stem cells since the late 1950s.
Fun facts
Some cells are huge: Caulerpa, a seaweed, is a single cell that can grow metres long.
Mitochondria have their own DNA, and you inherit it only from your mother.
An ostrich egg’s yolk is a single cell, one of the biggest on Earth.
Not all cells are tiny: the nerve cells running from your spine to your toes can be about a metre long.
Some of your cells almost never divide again: most heart muscle cells last you nearly your whole life.
Some bacteria thrive in boiling hot springs, others in ice, and one kind even survives the radiation in nuclear reactors.
Your red blood cells have no nucleus and can’t divide, so stem cells in your bone marrow make about 2 million new ones every second.
Story: Tiny Creatures in His Teeth
Tiny Creatures in His Teeth
1670s, Delft. Cloth merchant Antonie van Leeuwenhoek grinds tiny lenses as a hobby, and makes the best microscopes of his day.
He scrapes the plaque from his teeth, takes a look, and sees crowds of little creatures, “very prettily a-moving”.
London’s Royal Society doubted him, until witnesses confirmed what he saw. He had discovered bacteria.
True or false?
Tap your answer to see if you got it, and why.
-
Question 1 of 10
All living things are made of cells.
Show the answer
True. From bacteria to blue whales.
-
Question 2 of 10
The nucleus holds a cell’s DNA.
Show the answer
True. Like a control centre.
-
Question 3 of 10
Plant cells have a cell wall.
Show the answer
True. It keeps them stiff.
-
Question 4 of 10
Van Leeuwenhoek was the first to see bacteria.
Show the answer
True. Through microscopes he built himself.
-
Question 5 of 10
Cells multiply by dividing.
Show the answer
True. One cell becomes two.
-
Question 6 of 10
Most bacteria are harmless or helpful.
Show the answer
True. Only a small share cause disease.
-
Question 7 of 10
Stem cells can become different types of cell.
Show the answer
True. That’s what makes them special.
-
Question 8 of 10
Every living thing is made of many cells.
Show the answer
False. Bacteria are single cells.
-
Question 9 of 10
The cell membrane is where energy is released from food.
Show the answer
False. That happens in the mitochondria.
-
Question 10 of 10
Animal cells contain chloroplasts.
Show the answer
False. Only plant and algae cells do.
Keep going in the app
KnowSoda learns what you know and brings back what you’re about to forget. Cells has 6 more ideas at the Advanced and Expert levels.
Sources
- Nature Education (Scitable) — Cell biology
- Sender, Fuchs & Milo (2016), revised estimates for human and bacterial cells, PLoS Biology
- Royal Society — Robert Hooke’s Micrographia and Antonie van Leeuwenhoek
- NIH — Stem cell basics
- National Human Genome Research Institute — Mitochondria; apoptosis
- Johns Hopkins Medicine — The legacy of Henrietta Lacks
