The Itty-Bitty Club

A 3D tour inside one cell for children about five to eight. The camera looks into a child's cheek and on into one cheek cell, cut open like a picture book: the membrane, the nucleus and its DNA, the ribosomes, the ER and the Golgi, the mitochondria making energy, the recyclers and the cytoskeleton. It goes inside a mitochondrion and inside the nucleus, follows a recipe as it becomes a protein, and visits a gum-leaf cell with its cell wall. Free, with no ads and no sign-ups.

What your child will learn

• We're made of cells: tiny building blocks, too small to see, and we have trillions of them.
• The membrane is a thin skin round each cell, the gatekeeper: it lets useful things in and keeps harmful things out. Inside is the cytoplasm, like jelly.
• The nucleus is the command centre. It holds the DNA, the cell's recipe book, shaped like a twisted ladder. A copy of one recipe goes out through a little pore.
• Ribosomes are the builders: they read the recipe and join the pieces into a protein. The ER finishes it, the Golgi packs it into a bubble parcel (a vesicle), and it goes out through the membrane.
• Mitochondria are the powerhouses. They use food and air to make ATP, tiny energy packets, with little turning wheels on their folds. Busy cells, like muscle cells, have thousands.
• Lysosomes recycle worn-out parts, and the cytoskeleton holds the cell's shape, like scaffolding and roads.
• Plant cells have a cell wall, green chloroplasts and a big water bag; our cells don't have a cell wall. A cell grows by copying its DNA and splitting in two, which is how we grow and heal.

How it works

Story. A koala tells it in nine short chapters. The camera flies in close to the child's cheek and on, through a picture-book circle, into one cell. Inside the nucleus, one chromosome unwinds into the DNA ladder, and a pink copy of a recipe slips out through a pore; the chapter waits for it. A ringed recipe then goes to a ribosome, which joins beads into a protein; along the ER, up through the Golgi, into a bubble parcel, and out through the membrane, with the camera following. Inside a mitochondrion, sugar and oxygen come in and little wheels turn, popping out ATP sparks. The recyclers and the cytoskeleton come next, then a gum-leaf cell with its thick wall. The kookaburra drops in as the cell copies its DNA and splits in two. Every word is spoken and shown.

Explore. Turn the cell round, peek inside (the front of the membrane fades away), or tap any part to hear its name and what it does. Tap a mitochondrion or the nucleus to go inside it. Plant cell turns the page to the gum-leaf cell and back. Four buttons: Power (ATP sparks from a mitochondrion), Build (a ribosome builds a protein), Tidy (a lysosome recycles a worn-out part) and Split (one cell becomes two). Follow a recipe takes one from the DNA to the membrane, again and again, and What's this? shows the parts one at a time, including the close-ups and the leaf cell.

Quiz. Six picture questions, read aloud, so it works before your child can read. A wrong answer greys out and they have another go; nothing is ever lost. Finishing brings a new animal for their My mob book, and a card of the words they now know.

The real words it teaches

The tour uses the real names for the parts, and says what each one means the first time. These are on the card at the end, and a tap on each says what it means. The cytoplasm, ER, Golgi, vesicles, lysosomes, cytoskeleton, chloroplasts, vacuole, cristae, ATP synthase and chromosomes are named in the story and in Explore, but kept off the card.

• Cell: a tiny building block. You're made of trillions!
• Membrane: the thin skin round a cell: the gatekeeper.
• Nucleus: the cell's command centre.
• DNA: the cell's recipe book, shaped like a twisted ladder.
• Mitochondria: the powerhouses that make the cell's energy.
• ATP: tiny energy packets that power the cell's jobs.
• Ribosome: a builder that makes proteins.
• Cell wall: a stiff wall round a plant cell. People don't have one!

A note on the age

In the Australian Curriculum, cells are Year 8 science: students "recognise cells as the basic units of living things, compare plant and animal cells, and describe the functions of specialised cell structures and organelles" (AC9S8U01). This tour reaches well above five to eight on purpose. It gives each part one job a young child can hold on to, with its real name, and leaves the chemistry here for you. A nickname (the command centre, the powerhouse) is always said with what the part really does.

For grown-ups: the cell, in detail

The cell is drawn big and simple, and cut open like a picture book. What it shows, cartoon but true:

1. How many cells. Children's sources often say "more than 75 trillion"; a 2013 study estimated about 37.2 trillion, and counts vary with body size and method. The tour says "trillions", which is true either way. Most human cells are 10 to 100 micrometres across. A cheek cell, scraped gently from inside the mouth, is the classic first cell seen under a school microscope.
2. The membrane is a double layer of phospholipids with proteins in it: channels, pumps and receptors. It's selectively permeable: some things cross freely, others only through particular proteins.
3. The nucleus is wrapped in a double envelope with nuclear pores. It holds the DNA as chromatin, which packs into visible chromosomes (46 in most human cells) only when the cell gets ready to divide. The nucleolus makes the parts of ribosomes. A gene is copied into messenger RNA (transcription), which leaves through a pore; a ribosome reads it and joins amino acids into a protein (translation). The tour's "recipe" is the mRNA.
4. The endomembrane system. The rough ER is dotted with ribosomes; new proteins are threaded into it and folded. The smooth ER makes lipids. The Golgi sorts, tags and packages proteins into vesicles, some of which fuse with the membrane and release their contents outside the cell. Lysosomes hold digestive enzymes, at a low pH, and break down worn-out organelles and other material for reuse.
5. Mitochondria carry out most of cellular respiration: glucose is broken down in steps (the first in the cytoplasm), and in the mitochondria the energy is used, with oxygen, to make ATP. The inner membrane is folded into cristae, packed with the electron transport chain and ATP synthase, a rotary enzyme turned by a flow of hydrogen ions. Mitochondria have their own small loop of DNA. Muscle cells can hold thousands.
6. The cytoskeleton is a network of protein fibres (microfilaments, intermediate filaments and microtubules) that holds the cell's shape. Motor proteins walk vesicles along microtubules, the tour's "roads".
7. Plant cells add a cell wall of cellulose outside the membrane, chloroplasts for photosynthesis (carbon dioxide and water, with light, into sugar and oxygen) and a large central vacuole. Water pressure in the vacuole (turgor) pushes out against the wall; when a plant is short of water, the vacuoles shrink and it wilts.
8. Cell division. In mitosis, a cell copies its DNA, lines up the chromosomes, pulls a copy of each to either end, and pinches in two. It's how we grow and how tissues repair, like skin after a graze. It takes around an hour, far slower and tidier than the tour's quick split.
9. Not every cell looks like this one. There are hundreds of kinds of cell in the body. Red blood cells, for example, have no nucleus at all, and nerve cells can be very long.

Also left out: peroxisomes, centrioles and the nucleolus by name, the steps of respiration and photosynthesis, meiosis, and cells that aren't working as they should.

What it practises

• My body. How the body works, and the real names of its parts: the heart's atria and ventricles, arteries and veins (the Lub-Dub Club).
  AC9S1U01 (Science, Year 1); AC9HPFM03 (Health and Physical Education, Foundation)

The codes are from the Australian Curriculum v9 (Foundation to Year 1). Each links to the official wording. The cell itself is Year 8 (AC9S8U01), above.

Things to try together

• Look at a leaf, or a thin slice of onion skin, with a magnifying glass or a toy microscope. Onion skin shows plant cells, with their walls, as little bricks.
• Make a cell in a bowl of jelly: a plum for the nucleus, jelly beans for the mitochondria, sprinkles for the ribosomes. Name each part as it goes in.
• Stand very still, then run on the spot: which of your cells need more energy now? (Muscle cells, full of mitochondria.)
• Look at a graze healing over a week: new cells, made by splitting in two, are filling it in.
• The sheet to print has a cell to label, the parts to match to their jobs, and animal or plant to tick, with space to draw your own cell.

For every child, and every body

The tour is about how a cell works, not about anything going wrong: there's nothing about illness, faulty cells or genetic conditions. The one hurt it mentions is a graze healing. Food and air give cells their energy, with no food good or bad. The child is never shrunk or sent inside: the camera looks, and the recipe, the protein and the ATP do the moving. Nothing in a cell is said to want or decide anything. Our cells are only said to lack one thing, truthfully: a cell wall. Every body is made of cells working in its own way.

• Every word is spoken and written, so it works with the sound on or off.
• It works with a keyboard: the arrow keys turn the cell in Explore, and What's this? steps through the parts.
• Everything has its own shape as well as colour: the recipe is a ribbon, a protein a chain of beads, ATP a lightning spark, a vesicle a bubble, the wall a thick frame, and the wheels have paddles.
• If your device asks for less motion, the camera cuts instead of flying, the page turns without the iris, and nothing spins or wobbles.

What's simplified, and why

• The cell is drawn big and cut open at the front, like a picture book.
• Sizes are for seeing, not to scale: a real mitochondrion is far smaller beside the nucleus.
• One cell stands for all of a person's cells, which come in many kinds.
• The plant cell is shown on its own page, reached through the Plant cell button, rather than beside ours.
• The ATP synthase wheels are drawn big, facing us like waterwheels, on little stalks beside the folds, so their turning shows; really they sit in the folded inner membrane and are far too small to see.
• ATP is drawn as a lightning spark, and one spark pops out with each turn of the big wheel.
• Sugar and oxygen are drawn going straight into the mitochondrion; really, sugar is broken down in steps first.
• Inside the nucleus, one chromosome unwinds into the DNA ladder, and the copy (the recipe, mRNA) is drawn as a pink ribbon beside it; really, DNA inside a working nucleus is mostly unpacked, and chromosomes are packed tight like this when a cell is about to divide.
• The recipe's journey is drawn as one line: out of a pore, onto one ribosome, along the ER, up through the Golgi, and out in one bubble parcel. Really, many ribosomes read each recipe, and proteins take many routes.
• The protein is drawn as a short chain of beads that folds up; real proteins are chains of hundreds of building blocks (amino acids).
• The split is drawn simply: the DNA glows as it's copied, then a copy of the whole cell moves apart from it. Really, the chromosomes are shared out first, and the cell pinches in two over about an hour.
• The worn-out part the recyclers break down is drawn as a small grey bean.
• The cytoplasm is called 'jelly'; the source says it is mostly water with a semi-solid consistency.
• 'Command centre', 'powerhouse', 'factory', 'post office', 'recyclers', 'builders', 'gatekeeper' and 'recipe book' are nicknames, each said with what the part really does.

Where the facts come from

Every fact the tour states was checked against the page linked beside it.

• "The cell is the smallest unit with the basic properties of life." "Most cells are very small. For example, about 10,000 human cells could fit on the head of a pin."
  In the tour: You're made of cells: tiny building blocks, too small to see. (Tap: A cell: a tiny building block. Card: Cell: a tiny building block. Quiz: What are you made of? Cells.)
  Britannica Kids — cell
• "Human beings are made up of more than 75 trillion cells."
  In the tour: You have trillions of them! Let's look inside one. Every cell in you has jobs to do. (Taps: You! You're made of trillions of tiny cells. A cell: a tiny building block. You're made of trillions of them! Card: You're made of trillions!)
  Britannica Kids — cell
• A 2013 study estimated 37.2 trillion cells in the human body.
  In the tour: (For the guide: the 37.2 trillion estimate, and why sources differ. 'Trillions' is true either way.)
  Smithsonian — There are 37.2 trillion cells in your body
• Cheek cells, scraped gently from the inside of the cheek, are seen under a microscope: "Cells should be visible, but they will be small"; "Label the nucleus, cytoplasm, and cell membrane."
  In the tour: This is a cell from inside your cheek. (Tap: Your cheek. Inside it are lots of cells, too small to see. Quiz: Your cheek cell.)
  The Biology Corner (LibreTexts) — Observing Human Cells
• The cell membrane "allows useful substances to enter the cell. But it blocks the entry of harmful substances."
  In the tour: The membrane: a thin skin all round it. It's the gatekeeper, letting useful things in, and keeping harmful things out. (Tap: the same. Card: Membrane: the thin skin round a cell: the gatekeeper. Close it up: The membrane wraps round the whole cell, like a soft skin.)
  Britannica Kids — cell
• The cytoplasm is "70 to 80 percent water", with "a semi-solid consistency", and the organelles sit in it.
  In the tour: (Tap: The cytoplasm: the jelly inside the cell, where all the parts float and work.)
  OpenStax Biology 2e — 4.3 Eukaryotic Cells
• The nucleus "acts as the control center of the cell."
  In the tour: This big round part is the nucleus: the command centre. (Tap: It holds the DNA, the cell's instructions. Card: Nucleus: the cell's command centre. Quiz: Which part is the command centre? The nucleus.)
  Britannica Kids — cell
• DNA is "the instructions for how to make the body"; "DNA looks like a twisting ladder"; "DNA is stored in the chromosomes that are inside every cell of the body."
  In the tour: Inside is DNA, the cell's recipe book. DNA is shaped like a twisted ladder. (Tap and card: DNA: the cell's recipe book, shaped like a twisted ladder.)
  KidsHealth (kids) — What Is DNA?
• The bases' order "forms a code that tells cells to make certain kinds of proteins"; the strands "form a shape like a ladder that has been twisted into a spiral"; "DNA is found in structures of the cell called chromosomes."
  In the tour: Each recipe tells the cell how to make something. A copy of one is going out! (Tap: Chromosomes: DNA, packed up tight.)
  Britannica Kids — DNA
• "Chromosomes are only visible and distinguishable from one another when the cell is getting ready to divide"; otherwise the DNA is an "unwound, jumbled bunch of threads" (chromatin). The nuclear pores "control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm."
  In the tour: (Tap: Chromosomes: DNA, packed up tight. When a cell gets ready to split, they look like little X shapes. The close-up shows the chromosomes packed, and one unwinding.)
  OpenStax Biology 2e — 4.3 Eukaryotic Cells
• A recipe analogy for genes: the cell makes a temporary copy (messenger RNA); "RNAs are small enough to exit the nucleus through a small pore in the membrane"; the mRNA is "read by the ribosome", and proteins are like "pearls on strings", the amino acids being the pearls.
  In the tour: A copy of one is going out! Ribosomes are the builders. They read the recipe, and join the pieces into a protein. (Taps: A pore: a little door in the nucleus, where recipes go out. A recipe: a copy of one part of the DNA, going out to a ribosome to be read. Follow: A recipe, copied from the DNA, leaves the nucleus. A ribosome reads it, and builds a protein. Build button.)
  Ask A Biologist — Turning DNA into Proteins
• "Ribosomes are the cellular structures responsible for protein synthesis."
  In the tour: (Card: Ribosome: a builder that makes proteins. Quiz: Which part builds proteins? A ribosome.)
  OpenStax Biology 2e — 4.3 Eukaryotic Cells
• New proteins go into the rough ER, "where they undergo structural modifications, such as folding"; "Sorting, tagging, packaging, and distributing lipids and proteins takes place in the Golgi apparatus"; vesicles "fuse with the plasma membrane and release their contents outside the cell".
  In the tour: The protein goes into the ER: the factory, all folded up. Then to the Golgi, the post office. It packs the protein into a bubble parcel called a vesicle. Off it goes, out through the membrane! (Taps: ER, Golgi, vesicles. Follow: Into the ER, to be finished. The Golgi packs it in a bubble. Out it goes, through the membrane!)
  OpenStax Biology 2e — 4.4 The Endomembrane System and Proteins
• "Mitochondria are often referred to as the powerhouses of the cell"; they are "involved in releasing energy from food" (glucose + oxygen → carbon dioxide + water + energy, into ATP); "Cells that need a lot of energy, like muscle cells, can contain thousands of mitochondria."
  In the tour: These bean shapes are mitochondria: the powerhouses of the cell. They use the food you eat and the air you breathe to make energy. Busy cells, like muscle cells, have thousands of them! (Taps: mitochondria; sugar and oxygen. Card: Mitochondria. Chapter 9: The food you eat and the air you breathe give your cells the energy for their jobs.)
  Science Learning Hub — Mitochondria, cell powerhouses
• Mitochondria "are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule"; "The inner layer has folds called cristae."
  In the tour: It's all folded up inside, with lots of little wheels on the folds. The cell uses ATP to power its jobs. (Taps: cristae; ATP: a tiny energy packet. Card: ATP: tiny energy packets that power the cell's jobs. Quiz: What do mitochondria make? Energy, called ATP. Power button.)
  OpenStax Biology 2e — 4.3 Eukaryotic Cells
• ATP synthase "acts as a tiny generator"; "The turning of parts of this molecular machine facilitates the addition of a phosphate to ADP, forming ATP." At the end of the chain, electrons reduce "an oxygen molecule".
  In the tour: The wheel turns, and makes ATP: tiny energy packets. Zap! (Tap: ATP synthase: a tiny turning wheel. As it turns, it makes ATP.)
  OpenStax Biology 2e — 7.4 Oxidative Phosphorylation
• ATP synthase "lies across the inner mitochondrial membrane"; its particles "pepper the inner mitochondrial membrane" and "self-arrange into long rows at the end of the cristae".
  In the tour: It's all folded up inside, with lots of little wheels on the folds. (Tap: Cristae: the folds inside a mitochondrion, dotted with little ATP wheels.)
  Wikipedia — ATP synthase
• "The lysosomes are the cell's 'garbage disposal.'" Their enzymes break down proteins, sugars, fats, nucleic acids "and even worn-out organelles"; lysosomes are "the digestive component and organelle-recycling facility of animal cells".
  In the tour: Lysosomes are the recyclers. They break down worn-out parts, to use again. (Tap: the same. Tidy button.)
  OpenStax Biology 2e — 4.3 Eukaryotic Cells
• The cytoskeleton is "a network of protein fibers that help maintain the cell's shape"; microtubules "provide a track along which vesicles move through the cell".
  In the tour: The cytoskeleton: thin threads, like scaffolding, holding the cell's shape. And roads, too! Parcels travel along them. (Tap: the same.)
  OpenStax Biology 2e — 4.5 The Cytoskeleton
• "The Koala has a highly specialised diet made up of the leaves of certain species of eucalypts."
  In the tour: I love gum leaves! Leaves are made of cells too, but plant cells are a bit different. (Plant cell: A plant cell, from a gum leaf!)
  Australian Museum — Koala
• "In plant cells, a rigid wall surrounds and protects the cell membrane. The wall is made of a woody substance called cellulose. A plant's cell walls make the plant stiff enough to grow tall." "Chlorophyll helps plants make food from the energy in sunlight."
  In the tour: I love gum leaves! Leaves are made of cells too, but plant cells are a bit different. Plant cells have a cell wall: a stiff wall outside the membrane. Your cells don't have one. The wall keeps the cell's shape, and helps a plant stand up tall. Green chloroplasts make food from sunlight, and a big bag of water keeps the cell plump. (Taps: cell wall, chloroplasts. Card: Cell wall. Plant cell: See its stiff cell wall?)
  Britannica Kids — cell
• "Plant cells have a cell wall, chloroplasts and other specialized plastids, and a large central vacuole; whereas, animal cells do not." The wall "protects the cell, provides structural support, and gives shape to the cell"; when the central vacuole loses water it "leaves the cell wall unsupported" and the plant wilts.
  In the tour: Your cells don't have one. …a big bag of water keeps the cell plump. (Taps: cell wall: Your cells don't have one! Vacuole. Card: People don't have one! Plant cell off: no cell wall, just a soft membrane. Quiz: Which cell has a cell wall? A leaf cell.)
  OpenStax Biology 2e — 4.3 Eukaryotic Cells
• "Cells also divide so living things can grow." "When you skin your knee, cells divide to replace old, dead, or damaged cells." "The parent cell is also making a copy of its DNA to share equally between the two daughter cells." "A single cell divides to make two cells."
  In the tour: To grow, a cell copies its DNA, and splits in two. That's how you grow bigger, and how a graze heals. (Split button: One cell becomes two. Quiz: How does a cell make more cells? It splits in two.)
  Ask A Biologist — Cell Division
• Year 8: "recognise cells as the basic units of living things, compare plant and animal cells, and describe the functions of specialised cell structures and organelles".
  In the tour: (For the guide: where cells sit in the curriculum.)
  QCAA — Year 8 Science (AC9S8U01)

Every word it says

The whole script, for reading along, or for a child who'd rather read than listen.

1. Itty-bitty you

• Hello! I'm Koala. Let's go on a tiny adventure!
• You're made of cells: tiny building blocks, too small to see.
• You have trillions of them! Let's look inside one.
• This is a cell from inside your cheek.
• The membrane: a thin skin all round it. It's the gatekeeper, letting useful things in, and keeping harmful things out.

2. The command centre

• This big round part is the nucleus: the command centre.
• Inside is DNA, the cell's recipe book.
• DNA is shaped like a twisted ladder.
• Each recipe tells the cell how to make something. A copy of one is going out!

3. Build it, pack it, post it

• Ribosomes are the builders. They read the recipe, and join the pieces into a protein.
• The protein goes into the ER: the factory, all folded up.
• Then to the Golgi, the post office. It packs the protein into a bubble parcel called a vesicle.
• Off it goes, out through the membrane!

4. The powerhouses

• These bean shapes are mitochondria: the powerhouses of the cell.
• They use the food you eat and the air you breathe to make energy.
• Busy cells, like muscle cells, have thousands of them!

5. The ATP wheel

• Let's look inside a mitochondrion!
• It's all folded up inside, with lots of little wheels on the folds.
• The wheel turns, and makes ATP: tiny energy packets. Zap!
• The cell uses ATP to power its jobs.

6. Tidy and strong

• Lysosomes are the recyclers. They break down worn-out parts, to use again.
• The cytoskeleton: thin threads, like scaffolding, holding the cell's shape.
• And roads, too! Parcels travel along them.

7. Walls for plants

• I love gum leaves! Leaves are made of cells too, but plant cells are a bit different.
• Plant cells have a cell wall: a stiff wall outside the membrane. Your cells don't have one.
• The wall keeps the cell's shape, and helps a plant stand up tall.
• Green chloroplasts make food from sunlight, and a big bag of water keeps the cell plump.

8. One, two!

• Hello, Kookaburra!
• To grow, a cell copies its DNA, and splits in two.
• That's how you grow bigger, and how a graze heals.

9. All working together

• Every cell in you has jobs to do.
• The food you eat and the air you breathe give your cells the energy for their jobs.
• Welcome to the Itty-Bitty Club!

The quiz

Quiz time! Let's see what you remember. The right answers are in bold.

1. What are you made of? (Cells / Sand / Feathers)
2. Which part is the command centre? (A mitochondrion / The nucleus / A vesicle)
3. What do mitochondria make? (Hair / Bubbles of air / Energy, called ATP)
4. Which part builds proteins? (A ribosome / The membrane / The cell wall)
5. Which cell has a cell wall? (Your cheek cell / A leaf cell / Both)
6. How does a cell make more cells? (It shrinks / It pops / It splits in two)

What it needs, and what we collect

A recent browser on a phone, tablet or computer. The first visit downloads about 10 MB, and after that it keeps working with no signal. Nothing about your child is collected: the My mob card and the sound setting are kept on your own device. The privacy page has the whole story.

More in the series: What Makes Me, with the Lub-Dub Club, the Huff-Puff Club, the Munch-Crunch Club, the Mix-Fix Club, the Zip-Zap Club, the Drip-Drop Club, the Five-Alive Club, the Tickle-Prickle Club, the Click-Clack Club, the Heave-Ho Club and the Snap-Trap Club.