What are the parts of animal and plant cells, and how do cells build up into organisms?
The structure and function of the sub-cellular parts of animal and plant cells, the differences between them, and the levels of organisation from cells to tissues, organs and organ systems.
A focused answer to the WJEC GCSE Biology section 1.1 topic on cells, covering the sub-cellular structures of animal and plant cells, the differences between them, and the levels of organisation from cells through tissues and organs to organ systems and the whole organism.
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What this dot point is asking
WJEC wants you to name the sub-cellular structures of animal and plant cells, state what each one does, describe the differences between animal and plant cells, and put the levels of organisation in order from a single cell up to the whole organism.
The parts shared by animal and plant cells
Both animal and plant cells contain several structures, each with a job.
- Cell membrane: a thin layer around the cell that controls which substances enter and leave. It is partially permeable.
- Cytoplasm: a jelly-like material where most of the chemical reactions of the cell happen.
- Nucleus: contains the genetic material (DNA) as chromosomes and controls the activities of the cell.
- Mitochondria: the site of aerobic respiration, which releases energy for the cell. Cells that use a lot of energy, such as muscle cells, have many mitochondria.
- Ribosomes: the tiny structures where protein synthesis happens (proteins are made).
The extra parts in plant cells
Plant cells have everything an animal cell has, plus three extra structures.
- Cell wall: a strong outer layer made of cellulose. It supports the cell and gives it a fixed shape. Note that the cell wall is not the same as the cell membrane; the wall is outside the membrane.
- Chloroplasts: contain the green pigment chlorophyll and are the site of photosynthesis. They are found in the green parts of a plant, such as the leaf, but not in the roots.
- Permanent vacuole: a large space filled with cell sap. It keeps the cell firm (turgid), which helps support the plant.
Comparing animal and plant cells
The simplest way to compare them is a table of features.
| Structure | Animal cell | Plant cell |
|---|---|---|
| Cell membrane | Yes | Yes |
| Cytoplasm | Yes | Yes |
| Nucleus | Yes | Yes |
| Mitochondria | Yes | Yes |
| Ribosomes | Yes | Yes |
| Cell wall (cellulose) | No | Yes |
| Chloroplasts | No | Yes |
| Permanent vacuole | No | Yes |
A typical animal cell is a more rounded, flexible shape because it has no cell wall. A typical plant cell has a fixed, often boxy shape because the cellulose wall holds it rigid.
Levels of organisation
In a multicellular organism, cells do not work alone. They are organised into larger and larger structures.
- A cell is the basic unit.
- A tissue is a group of similar cells that work together to carry out a function. Examples include muscle tissue and the lining (epithelial) tissue of the gut.
- An organ is a group of different tissues working together to perform a job. The stomach is an organ that contains muscle tissue, glandular tissue (which makes enzymes) and epithelial tissue.
- An organ system is a group of organs that work together. The digestive system includes the stomach, small intestine, liver and pancreas.
- Several organ systems together make up the whole organism.
Why this matters
These levels of organisation set up the rest of the unit. The digestive, respiratory and circulatory systems you meet later are all organ systems built from organs, which are built from tissues, which are built from specialised cells.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC style4 marksDescribe two structures found in a plant cell that are not found in an animal cell, and give the function of each.Show worked answer →
A 4-mark structured question: two structures, each with a function, so one mark per named structure and one per function.
Choose two from: the cell wall, made of cellulose, which supports the cell and gives it a fixed shape; the chloroplasts, which contain chlorophyll and are the site of photosynthesis; the permanent vacuole, which contains cell sap and keeps the cell turgid (firm) to support the plant.
Markers reward a named structure with a correct function. A common slip is to name a structure that both cells share (mitochondria, ribosomes, nucleus), which earns no marks because the question asks for plant-only structures.
WJEC style3 marksPut these in order of increasing size and define the term tissue: organ, cell, tissue.Show worked answer →
A 3-mark question testing organisation. Order of increasing size: cell, then tissue, then organ.
A tissue is a group of similar cells that work together to carry out a particular function. For example, muscle tissue is made of muscle cells that contract together.
Markers reward the correct order (cell, tissue, organ) and a definition that says a tissue is a group of similar or specialised cells working together. Saying a tissue is simply many cells, without the idea of working together for one function, loses the definition mark.
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Sources & how we know this
- WJEC GCSE Biology specification (from 2016) — WJEC (2016)