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Comparing the similarities and differences between the cells of plants and animals.
Have you ever wondered why trees can grow hundreds of feet tall without having a skeleton like yours? The secret is hidden inside their tiny cells!
All living things are made of cells. Think of them as tiny 'rooms' that make up a body. Animal cells are usually round or irregular, like soft water balloons. Because animals move around, their cells need to be flexible. Plant cells are different. They are usually rectangular or square-shaped, like sturdy bricks in a wall. This fixed shape helps plants stay organized as they grow upward toward the sun. If you look at a leaf under a microscope, the cells look like a neat grid of boxes!
Quick Check
What is the typical shape of a plant cell compared to an animal cell?
Answer
Plant cells are rectangular or square-shaped, while animal cells are round or irregular.
Plants don't have bones to hold them up. Instead, every plant cell is surrounded by a tough, outer layer called the cell wall. This wall is like a suit of armor made of a strong material called cellulose. It provides support and protection. When you stack millions of these 'armored' cells together, they become strong enough to support heavy branches. Animal cells never have a cell wall; they only have a thin, flexible cell membrane.
Why doesn't a tree collapse in the wind? 1. Each cell has a rigid cell wall. 2. These walls act like tiny wooden boxes. 3. Millions of boxes stacked together create a trunk that can stand feet tall without a skeleton.
Quick Check
Which part of the plant cell provides it with a rigid structure?
Answer
The cell wall.
Have you noticed that most plants are green? That's because of chloroplasts. These are special parts found only in plant cells. Chloroplasts act like tiny solar panels. They capture energy from sunlight to make food (sugar) for the plant through a process called photosynthesis. Animals don't have chloroplasts because they get their energy by eating food instead of making it from the sun. Inside one leaf cell, there might be to of these green dots!
Imagine a cat and a sunflower: 1. The cat (animal cells) must find and eat a mouse to get energy. 2. The sunflower (plant cells) stays still and uses its chloroplasts to turn sunlight into energy. 3. Because the sunflower doesn't move, its cell walls keep it pointing toward the sun.
A scientist finds a cell that is perfectly square and has green spots inside. 1. The square shape tells us it has a cell wall. 2. The green spots tell us it has chloroplasts. 3. Conclusion: This must be a plant cell, not an animal cell!
Which of these is found in a plant cell but NOT in an animal cell?
Why do plant cells have a rectangular shape?
Animal cells have a cell wall to help them stay upright.
Review Tomorrow
In 24 hours, try to remember the two parts a plant cell has that an animal cell does not.
Practice Activity
Draw two pictures: one of a 'brick-like' plant cell with green dots, and one of a 'blob-like' animal cell. Label the cell wall and chloroplasts.