What Are Plant and Animal Cells?
Every living thing is built from cells — tiny units of life too small to see, packed with incredible machinery.
Cells: The Building Blocks of Life
Every living organism on Earth — from bacteria to blue whales — is made of cells. Some organisms like bacteria consist of just one cell. Your body, on the other hand, contains roughly 37 trillion cells, all working together. A cell is the smallest unit that can carry out all the functions of life: it takes in nutrients, converts them to energy, carries out specialized tasks, and reproduces. Think of cells as the bricks that build every living structure.
What Both Cell Types Share
Plant cells and animal cells are both eukaryotic — they have a nucleus surrounded by a membrane that holds the cell's DNA (the instruction manual for life). Both types also have a cell membrane that controls what enters and exits the cell, mitochondria that act as power plants converting nutrients into energy, ribosomes that build proteins, and a gel-like cytoplasm filling the cell's interior. These shared features reflect the fact that plants and animals share a common ancestor deep in evolutionary history.
What Makes Plant Cells Different
Plant cells have three major structures that animal cells lack. First, a rigid cell wall made of cellulose surrounds the cell membrane, giving plants their structural strength — it's why a tree trunk can stand tall without bones. Second, chloroplasts are organelles filled with the green pigment chlorophyll, which captures sunlight and converts it into food through photosynthesis. Chloroplasts are why plants are green. Third, plant cells typically have a large central vacuole — a huge, water-filled sac that can take up 90% of the cell's volume, maintaining pressure that keeps the plant upright.
What Makes Animal Cells Different
Animal cells are generally smaller and more irregularly shaped than plant cells (no rigid cell wall to enforce a box shape). They have centrioles — structures that help organize cell division — which most plant cells lack. Animal cells also have many small vacuoles instead of one giant one. Without cell walls, animal cells are more flexible, which is important for animals that need to move, contract muscles, and change shape.
Why This Matters
Understanding cells is the foundation of all biology. When you learn how cells work, you understand why plants need sunlight (chloroplasts), why you need to eat food (no chloroplasts — you can't make your own energy from sunlight), why cuts heal (cell division), and how diseases attack the body (by disrupting cell functions). Every medical breakthrough, from antibiotics to vaccines to cancer treatments, depends on understanding what happens inside cells.
The largest single cell in the world is an ostrich egg — it can be about 15 centimeters long and weigh up to 1.4 kilograms. At the other extreme, most human cells are between 10 and 30 micrometers across — so small that you'd need to line up about 1,000 of them to span one centimeter. Your red blood cells are even tinier: about 7 micrometers, so roughly 10,000 could fit on the head of a pin.
Last reviewed: April 2026