Cells
Have you ever looked closely at a brick wall? A massive building is just thousands of tiny bricks stacked together. Your body is built exactly the same way, but your "bricks" are alive!
Are You Made of Bricks?
Yes! Even after a tree is cut down, the wood is still made of the empty cell walls that once kept the tree alive. This means wooden buildings are actually being held up by cells!
No! Just like a house has different rooms for different purposes, your body has highly specialised cells. You have different cells for seeing, hearing, moving, and even thinking!
Put Your Instincts to the Test
Think about what you already know about living things. Pick an answer for each question, then see if your instincts were right.
Carrot cells have a rigid outer cell wall. Both plants and animals have flexible cell membranes, but only plant cells have a thick, rigid cell wall on the outside to give them structure so they can stand up without bones!
The vanilla molecules pass through microscopic holes in the balloon. The molecules are so incredibly small they slip right through the solid rubber. This is similar to how your cells absorb chemicals through their membrane, a process called osmosis!
Every single day. We shed millions of dead skin cells every day, and millions of new ones are constantly being born to replace them! Your body is constantly refreshing itself.
Understanding the Science
Tap each card to learn about the tiny, living compartments that make up every living thing on Earth.
Key Concepts
The Cell
Tap to learn moreCells are the tiny, living building blocks of all plants and animals. Just like a brick wall is made of single bricks, you are made of trillions of microscopic cells stacked together.
Specialised Cells
Tap to learn moreNot all cells are the same. Your body has many different types of cells with specific jobs, such as red blood cells to carry oxygen, nerve cells to send signals, and muscle cells for movement.
The Nucleus
Tap to learn moreThis is the control centre of the cell. It acts like the brain or the boss's office, holding the DNA instructions and telling the rest of the cell exactly what to do.
Mitochondria
Tap to learn moreThese are the powerhouses of the cell. Just like a fireplace provides heat for a room, mitochondria provide the energy that the cell needs to survive and do its job.
Cell Membrane
Tap to learn moreThis is the flexible outer skin of an animal cell. It protects the inside of the cell and controls what chemicals and nutrients are allowed to pass in and out.
Cell Walls
Tap to learn morePlant cells have a cell membrane, but they also have a tough, rigid cell wall on the very outside. This is what allows trees and plants to stand up tall without having a skeleton!
Mitosis
Tap to learn moreCells reproduce by dividing. One parent cell splits into two identical baby cells. This process, called mitosis, is how living things grow and how they heal from injuries.
DNA & Genes
Tap to learn moreDeoxyribonucleic Acid (DNA) is a very long molecule inside the nucleus. Genes are specific sections of DNA that act like a chemical instruction manual, deciding everything from your eye colour to what job a cell will do.
Try It: Interactive Cell Explorer
Click on the different parts of the detailed plant and animal cells below to explore their organelles and find out what jobs they do!
Try It: Interactive Cell Explorer
Click on the different parts of the detailed plant and animal cells below to explore their organelles and find out what jobs they do!
Select a Cell
Click the buttons above to switch cell types, then click on the specific organelles inside the cross-section to identify them!
Apply Your Knowledge
Now let us see if you can connect what you have learned to the real world.
Match the Cell Parts
Click an object to select it, then click the matching description to place it.
Real-World Challenge
Imagine you are a scientist trying to figure out if a mysterious, unmoving green blob you found in a pond is actually a living creature. Based on what you learned in this episode, what would you look for under a microscope to prove it is alive? What specific organelles might you see because it is green?
What Has Changed Since This Episode Aired
This episode of Bill Nye the Science Guy first aired in the 1990s. While the biology of a cell remains accurate, modern science has made some incredible discoveries about how many cells we actually have!
Updated: Actually, it is closer to 37 trillion cells! Why the huge change? This is a perfect example of the scientific method in action. In 1993, scientists used the best estimations they had. Today, with advanced imaging and biological modelling, we have much more accurate counts. Science is not about being perfect the first time; it is about constantly refining answers. As our tools get better, our numbers get closer and closer to the absolute truth. That is what makes science great!
Updated: We now know that you are only about half human! Your body is also home to roughly 39 trillion bacterial cells (your microbiome). These friendly microbes live mostly in your gut and are absolutely essential for helping you digest food and stay healthy.
Updated: We have since discovered a fascinating field called "Epigenetics." Scientists now know that while your core DNA code does not change, your environment, diet, and lifestyle can actually turn certain genes "on" or "off" like a light switch!
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
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Reflection
The episode showed that many of the foods we eat (like yoghurt, cheese, and bread) are actually made with the help of living cells (bacteria and yeast). Does knowing that there are living things involved in making your food change how you think about it? Why or why not?
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