Biology · Cell Structure
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Animal and Plant Cells
Animal and plant cells are eukaryotic, so they share a nucleus and several other structures. This lesson names each sub-cellular structure, says what it does, and shows what plant cells have that animal cells do not.
Learning Objectives
- 1Name the main sub-cellular structures in animal cells and plant cells.
- 2Explain how each structure is related to its function.
- 3Describe the differences between animal cells and plant cells.
- 4Explain why some cells contain more of a structure than others.
Retrieval practice
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1
What is the main difference between a eukaryotic and a prokaryotic cell?
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A eukaryotic cell has its DNA in a nucleus. A prokaryotic cell does not.
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2
What is 1 µm in metres?
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\(1 \times 10^{-6}\text{ m}\), one millionth of a metre.
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3
Name the structure that surrounds the cytoplasm of every cell.
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The cell membrane.
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4
Is a bacterium a eukaryote or a prokaryote?
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A prokaryote.
Sub-cellular structures in an animal cell
Most animal cells have these five structures. Each one has a job.
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Nucleus
Contains the genetic material (DNA) and controls the activities of the cell.
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Cytoplasm
A jelly-like liquid where most of the cell's chemical reactions take place.
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Cell membrane
Controls which substances pass into and out of the cell.
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Mitochondria
Where aerobic respiration takes place, releasing the energy the cell needs.
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Ribosomes
Where proteins are made, by joining amino acids together.
An animal cell
An animal cell, with its main sub-cellular structures labelled.
What plant cells have as well
Plant cells have everything an animal cell has, plus three more structures. Not every plant cell has all three: root cells have no chloroplasts, for example.
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Cell wall
A rigid layer of cellulose outside the cell membrane. It strengthens the cell and supports the plant.
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Chloroplasts
Contain the green pigment chlorophyll, which absorbs light for photosynthesis. Found in the green parts of a plant.
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Permanent vacuole
A large space filled with cell sap, a solution of sugars and salts. It helps keep the cell firm.
A plant cell
A plant cell. The structures that animal cells lack are the cell wall, chloroplasts and permanent vacuole.
Animal cells and plant cells compared
Animal cell
- Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
- No cell wall, so the shape can change
- No chloroplasts, so it cannot photosynthesise
- Usually no large permanent vacuole
Plant cell
- Has all of those structures too
- Cellulose cell wall gives a fixed shape
- Chloroplasts in the green parts, for photosynthesis
- Large permanent vacuole filled with cell sap
Case study
Palisade cells in a leaf
The palisade layer sits near the top of a leaf, where the most light arrives. Its tall, tightly packed cells contain a huge number of chloroplasts. That means each cell can absorb a lot of light for photosynthesis, which is exactly the job of the leaf. A cell in a root, which is underground in the dark, has no chloroplasts at all.
Link the structure to the job
In the exam you are often asked why a cell has lots of one structure.
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Muscle cells
They contain many mitochondria, because contracting needs a lot of energy from respiration.
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Cells making lots of protein
They contain many ribosomes, because ribosomes are where proteins are made.
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Leaf cells
They contain many chloroplasts, because they carry out most of the plant's photosynthesis.
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Storage cells in plants
They have a large permanent vacuole to hold cell sap.
Common mistakes to avoid
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Mitochondria do not "make" energy
They release energy from glucose in respiration. Energy cannot be made, only transferred.
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The cell wall is not the cell membrane
Plant cells have both. The wall is rigid and cellulose. The membrane is thin and controls what passes in and out.
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Not every plant cell has chloroplasts
Only the cells exposed to light, such as leaf cells, have them.
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Ribosomes are not the nucleus
The nucleus holds the instructions. Ribosomes use them to build proteins.
THE BIG IDEA
Structure always fits function: a cell has more of whatever its job needs most.
Animal and plant cells
Animal and plant cells
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Nucleus
- contains DNA
- controls the cell
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Cytoplasm
- chemical reactions happen here
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Cell membrane
- controls what moves in and out
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Mitochondria
- aerobic respiration
- release energy
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Ribosomes
- make proteins
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Plant only
- cell wall
- chloroplasts
- permanent vacuole
Summary and exam focus
- Animal cells have a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
- Plant cells also have a cell wall, chloroplasts and a permanent vacuole.
- Mitochondria are the site of aerobic respiration, and ribosomes make proteins.
- Chloroplasts absorb light for photosynthesis, and only some plant cells have them.
- Cells have more of the structures their job needs.
Exam focus
Explain why a muscle cell contains many mitochondria. (2 marks) (2 marks)
Link the structure to its function in two steps: say what mitochondria do, then why that matters for a muscle. Do not say mitochondria "produce energy".
Key terms
The words this lesson expects you to use. Each one is linked from the first place it appears above.
- Sub-cellular structure
- A structure inside a cell, such as the nucleus or a mitochondrion.
- Mitochondria
- Structures where aerobic respiration takes place, releasing energy for the cell.
- Ribosome
- A tiny structure where proteins are made.
- Chloroplast
- A structure in plant cells that contains chlorophyll and carries out photosynthesis.
- Chlorophyll
- The green pigment that absorbs light energy for photosynthesis.
- Permanent vacuole
- A space in a plant cell filled with cell sap.
- Cell sap
- A solution of sugars and salts stored in the permanent vacuole.
- Cellulose
- The strong material that plant cell walls are made of.
- Aerobic respiration
- A chemical reaction that uses oxygen to release energy from glucose.
- Photosynthesis
- The process in which plants use light to make glucose.
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