Animal Cells - GCSE Biology Definition

Key Takeaways

• Animal cells are eukaryotic cells, so their genetic material is enclosed in a nucleus.

• Most animal cells contain five main parts: a nucleus, cytoplasm, a cell membrane, mitochondria and ribosomes.

• Animal cells don't have a cell wall, chloroplasts or a permanent vacuole. Plant cells have a cell wall and a permanent vacuole, and many have chloroplasts.

• Most animal cells are between 10 and 100 micrometres (µm) across, so you need a microscope to see them.

• Many animal cells are specialised, with a structure that suits one particular job.

What Is an Animal Cell?

An animal cell is the basic building block of an animal's body. Your muscles, nerves and blood all contain animal cells. Understanding animal cell structure means knowing which structures a cell contains and what each of them does.

Animal cells are eukaryotic. That means their genetic material (DNA) is packaged inside a nucleus. Plant cells, fungi and protoctists are eukaryotic too. Bacteria are different: they're prokaryotic cells, with DNA found in the cytoplasm as a single loop rather than in a nucleus.

Animal cells are tiny. Scientists measure them in micrometres (µm), and there are 1000 µm in 1 mm. Most eukaryotic cells are between 10 and 100 µm across, and a human cheek cell is about 65 µm. That's far too small to see with the naked eye, so you'd need a light microscope.

Animal Cell Structure and Organelles

Most animal cells share the same set of sub-cellular structures. Some of these are organelles, meaning specialised structures within cells that carry out particular functions. Each part has its own job.

Nucleus

The nucleus contains the cell's genetic material (DNA). This DNA controls the activities of the cell. A common exam slip is calling the nucleus "the brain of the cell". An accurate description is that it controls the cell's activities.

Cytoplasm

Cytoplasm is a gel-like substance made of water and dissolved solutes. It supports the structures inside the cell. Many chemical reactions happen here, including anaerobic respiration. The cytoplasm contains the enzymes that make these reactions happen.

Cell membrane

The cell membrane holds the cell together and separates the inside from the outside. It controls which substances can enter and leave the cell.

Mitochondria

Mitochondria are the site of aerobic respiration. Respiration releases the energy the cell needs for its processes. Cells with high energy demands generally contain more mitochondria than less active cells.

Ribosomes

Ribosomes are small organelles found in the cytoplasm. They're the site of protein synthesis, by which the cell makes proteins.

Check out our specification-tailored animal and plant cell revision notes to consolidate what you've learned here, for example AQA GCSE Animal & Plant Cells Revision Notes. They're written by expert teachers and examiners and include labelled diagrams showing which structures you can see with each type of microscope.

Animal Cells Diagram

A labelled animal cell diagram usually shows a rounded cell outline (the cell membrane), a nucleus, cytoplasm, mitochondria and ribosomes. You'll often be asked to recognise, draw or label one.

With suitable staining, a light microscope can show larger structures such as the nucleus, cytoplasm and outline of an animal cell. Smaller structures, such as ribosomes, are too small to resolve with a light microscope – you need an electron microscope to see them.

Cheek cells are the animal cells most often viewed in class. They're stained with methylene blue so the cell structures stand out.

When you draw cells from a microscope, follow the rules for biological drawings:

• use a sharp pencil and clear, continuous lines

• don't use shading

• draw structures in proportion, as they appear

• draw label lines with a ruler, touching the structure and never crossing

• include a scale bar or the drawing’s magnification

Differences Between Plant and Animal Cells

Plant and animal cells are both eukaryotic, so they have many similar structures. Both contain a nucleus, cytoplasm, a cell membrane, mitochondria and ribosomes. 

Plant cells also have extra structures that animal cells lack.

Do animal cells have a cell wall?

No. Animal cells are surrounded only by a cell membrane. Plant cells also have a cell wall made of cellulose, which strengthens the cell and defines its shape. 

Do animal cells have chloroplasts?

No. Chloroplasts contain chlorophyll and the enzymes needed for photosynthesis, so animals can't photosynthesise. Instead, animals feed on organic substances made by other living things. Animal cells also lack a permanent vacuole filled with cell sap.

“Because plant cells have chloroplasts, I find that students often forget that they also have mitochondria, when in fact, they respire just like animal cells. A way to avoid this is to think of some cell components, like mitochondria or chromosomes, as the essential parts in a motor, without which it cannot run at all.”

– Natalie Lawrence, Biology Tutor

Specialised Animal Cells

Many animal cells become specialised through a process called differentiation. A specialised cell has a structure that helps it carry out a specific function. The adaptation might be the cell's shape, or which sub-cellular structures it contains.

Examples of animal cells that are specialised include:

Put these adaptations into practice with our AQA GCSE Cell Structure Exam Questions. Each question is written by expert teachers and examiners to match the specification, and you can check your answers against step-by-step mark schemes.

Frequently Asked Questions

Are animal cells eukaryotic or prokaryotic?

Animal cells are eukaryotic. Their genetic material is enclosed in a nucleus. Prokaryotic cells, such as bacteria, have no nucleus and are much smaller, often around 1 µm.

How big is an animal cell?

Most animal cells are between 10 and 100 micrometres (µm) across. A human cheek cell, for example, is about 65 µm. That makes a typical animal cell at least ten times bigger than many bacterial cells.

Do all animal cells have a nucleus?

Most do, but not all. Mature mammalian red blood cells have no nucleus, which leaves more room for haemoglobin to carry oxygen. Platelets, which help blood clot, are fragments of cells and also lack a nucleus.

Do animal cells have a cell wall?

Animal cells have a cell membrane but no cell wall. Plant and algal cells have a cellulose cell wall, which gives them extra support and defines their shape.

What structures do plant and animal cells have in common?

Both have a nucleus, cytoplasm, a cell membrane, mitochondria and ribosomes. Plant cells also have a cell wall and a permanent vacuole, and many contain chloroplasts.

Can you see an animal cell without a microscope?

Usually not. Most animal cells measure 10 to 100 µm, which is too small for the naked eye. With proper staining, the nucleus, cytoplasm and cell membrane can be seen with a light microscope. Smaller structures like ribosomes need an electron microscope.