Plant and Animal Cells

The big idea

Cells are the tiny units that make living things work. Plant and animal cells are both eukaryotic cells—cells with a nucleus and other membrane-bound organelles. Prokaryotic cells have no nucleus and no membrane-bound organelles, so they are built in a simpler way.

Think of a cell as a tiny city with a fence, a control office, power stations, and storage rooms. Each part has a job, and the whole cell works because those jobs fit together.

What you'll learn

• What the main organelles in plant and animal cells do
• Which structures only plant cells have
• How to tell plant cells from animal cells fast on a test
• How prokaryotic cells are different in one sentence

What both plant and animal cells share

Both cells are built on the same basic plan, like two different models of the same phone.

1. Membrane: The cell membrane is a thin, flexible barrier that controls what enters and leaves the cell. It keeps the inside stable while still letting the cell take in food, water, and oxygen.
2. Inside space: The cytoplasm is the jelly-like material inside the membrane. It holds the organelles in place and is where many chemical reactions happen.
3. Control room: The nucleus stores DNA, the instructions for the cell. It acts like the control center, telling the cell which proteins to make and when to make them.
4. Protein builders: Ribosomes are the tiny structures that build proteins. Some float freely in the cytoplasm, and some are attached to rough ER.
5. Energy makers: Mitochondria are the organelles that release usable energy from food during cellular respiration. That is why they are often called the cell's powerhouses.
6. Assembly and shipping: The endoplasmic reticulum (ER) helps make and move materials. Rough ER has ribosomes and helps with proteins; smooth ER helps make lipids and other molecules. The Golgi apparatus modifies, sorts, and packages materials for transport.
7. Small storage: Many cells also have vacuoles, which store water, food, and wastes. Animal cells usually have many small vacuoles instead of one huge one.

All of these parts work together to keep the cell alive, make proteins, and move energy and materials where they are needed.

What makes plant cells different

Plant cells have everything above, plus three structures that help them stand up and feed themselves. Use the diagram below to keep them straight.

The cell wall is the stiff outer layer outside the membrane. It is made of cellulose and gives the cell shape, support, and protection. The cell membrane is still there too; it sits just inside the wall and controls what enters and leaves.

The chloroplast is the organelle that captures light energy for photosynthesis. It contains chlorophyll, the green pigment that absorbs light. Chloroplasts are what make plant cells able to make sugar from sunlight, water, and carbon dioxide.

The large central vacuole is a huge storage sac filled with watery fluid. It stores water and dissolved substances, and it helps keep the plant cell firm by creating turgor pressure, the pressure of the vacuole pushing outward on the cell wall. That pressure is one reason plants stand upright.

The mitochondrion is also shown because plant cells use mitochondria too. Plants make sugar in chloroplasts, but they still need mitochondria to release usable energy from that sugar. The cytoplasm surrounds the organelles, and the ribosomes build proteins wherever they are needed.

That's the plant-cell plan: wall for support, chloroplasts for photosynthesis, and a large vacuole for storage and pressure.

What to remember about animal cells

Animal cells do not have a cell wall or chloroplasts, so they are more flexible in shape. They usually have smaller vacuoles, and many animal cells also have lysosomes, which break down waste and worn-out cell parts. Many animal cells have centrioles, which help organize cell division.

Because animal cells do not make their own food by photosynthesis, they depend on food molecules from other organisms. That is why mitochondria are so important in animal cells: they help turn those food molecules into usable energy.

Putting it together

Here is the whole comparison in one table — the three rows at the bottom are the ones tests ask about.

So if a cell has a wall, chloroplasts and one big vacuole, it's a plant cell. If it has none of those, it's an animal cell.

Check yourself

1. Which structure controls what enters and leaves the cell? Answer The cell membrane.
2. Why do plant cells need chloroplasts but animal cells do not? Answer Chloroplasts carry out photosynthesis, which plant cells use to make sugar from light.
3. What is one main job of the large central vacuole? Answer It stores water and helps keep the cell firm with turgor pressure.

Common mistakes

• "The cell wall and cell membrane are the same thing." No. The wall is the stiff outer support layer; the membrane is the thin gatekeeper just inside it.
• "Only animal cells have mitochondria." False. Both plant and animal cells have mitochondria.
• "Vacuoles are only tiny." Plant cells usually have one large central vacuole; animal cells usually have smaller vacuoles.

Remember this

• Plant cells have cell wall + chloroplasts + large central vacuole.
• Both plant and animal cells are eukaryotic and share the nucleus, membrane, cytoplasm, ribosomes, mitochondria, ER, and Golgi.
• Cell membrane controls in and out; cell wall supports; chloroplasts make sugar; mitochondria release energy.