1.2 Animal and Plant Cells

A free GCSE Biology lesson for AQA (8461) from OBA School: the sub-cellular structures of animal, plant and algal cells and what each one does. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Name the structures found in animal cells and describe what each one does
• Name the extra structures found in plant and algal cells and describe their functions
• Recognise animal and plant cells from diagrams and micrographs
• Estimate the size of a sub-cellular structure compared with the whole cell

Key words

• Eukaryotic cell: A cell with its genetic material inside a nucleus. Animal, plant, algal and fungal cells are all eukaryotic.
• Aerobic respiration: A reaction that uses oxygen to release energy from glucose. It happens in the mitochondria.
• Photosynthesis: A reaction that uses light energy to make glucose. It happens in the chloroplasts.
• Cellulose: A tough carbohydrate that makes up the cell walls of plants and algae.

Structures in animal cells

Most animal cells, such as the cells lining your cheek, have these five parts. They are also found in plant cells.

• Nucleus; Function Contains the genetic material (DNA in chromosomes) that controls the activities of the cell.
• Cytoplasm; Function A jelly-like liquid where most chemical reactions happen. These are controlled by enzymes.
• Cell membrane; Function Controls which substances move into and out of the cell.
• Mitochondria; Function Where most of the reactions of aerobic respiration happen, releasing energy for the cell.
• Ribosomes; Function Where proteins are made (protein synthesis).

Key fact: Ribosomes are tiny. You can only see them with an electron microscope. Mitochondria can just be seen with a good light microscope, but their detail needs an electron microscope.

Extra structures in plant and algal cells

Plant cells have all five animal-cell structures, plus three more. Algal cells (for example, the cells of seaweed or pond algae) also have a cellulose cell wall and chloroplasts.

• Chloroplasts; Function Contain chlorophyll, a green pigment that absorbs light for photosynthesis.
• Permanent vacuole; Function Filled with cell sap (a solution of sugars and salts). Keeps the cell firm (turgid), which helps to support the plant.
• Cell wall; Function Made of cellulose. Strengthens the cell and stops it bursting when it takes in water.

Exam tip: Not every plant cell has chloroplasts. Root cells are underground and get no light, so they have none.

Comparing animal and plant cells

• Nucleus, cytoplasm, cell membrane; Animal cell ✓; Plant cell ✓; Algal cell ✓
• Mitochondria and ribosomes; Animal cell ✓; Plant cell ✓; Algal cell ✓
• Cell wall (cellulose); Animal cell ✗; Plant cell ✓; Algal cell ✓
• Chloroplasts; Animal cell ✗; Plant cell ✓ (most, not roots); Algal cell ✓
• Permanent vacuole; Animal cell ✗ (only small, temporary ones); Plant cell ✓; Algal cell ✓

Worked example: spot the cell

A micrograph shows a cell with a regular box shape, a thick outer layer and a large clear space in the middle, but no chloroplasts.
The box shape and thick outer layer suggest a cell wall. The clear space is a permanent vacuole.
No chloroplasts means it gets no light, for example an onion bulb or root cell.

Answer: a plant cell from a part of the plant that gets no light

Estimating sizes in a cell

You can estimate the size of a structure by comparing it with something whose size you know, such as the whole cell or a scale bar. Measure both on the image, find how many times one fits into the other, then scale.

Worked example: estimating a nucleus

A cheek cell is 60 µm across. On a photo the cell is 48 mm across and its nucleus is 9.6 mm across.
The nucleus is 9.6 ÷ 48 = 0.2 of the cell width (one fifth).
Real width of nucleus ≈ 0.2 × 60 µm = 12 µm

Answer: about 12 µm

Key fact: Cells that need a lot of energy, such as muscle cells and sperm cells, contain many mitochondria. Leaf cells near the top surface contain many chloroplasts.

Common mistakes

• Saying the cell wall “controls what enters the cell”. That is the cell membrane. The cell wall is fully permeable and gives strength.
• Saying mitochondria “make energy”. Energy cannot be made. Respiration in mitochondria releases energy.
• Thinking all plant cells have chloroplasts. Root cells do not.
• Confusing the cell membrane and the cell wall in diagrams. In a plant cell the membrane is the thin line just inside the wall.
• Forgetting that algal cells, like plant cells, have cellulose cell walls and chloroplasts.

Revision questions

Try these, then check your answers below each one.

Question 1. Which structure is found in plant cells but not in animal cells? (Choose from: Mitochondria, Ribosomes, Cell wall, Cell membrane.)

Answer: Cell wall

Working: Only plant (and algal) cells have a cellulose cell wall. Both cell types have mitochondria, ribosomes and a cell membrane.

Question 2. True or false? All plant cells contain chloroplasts.

Answer: False

Working: False. Root cells are underground and get no light, so they have no chloroplasts.

Question 3. Name the sub-cellular structures where most of the reactions of aerobic respiration take place.

Answer: mitochondria

Working: Mitochondria (one mitochondrion) are where most aerobic respiration happens.

Related lessons

• Previous lesson: 1.1 The World of the Microscope
• Next lesson: 1.3 Eukaryotic and Prokaryotic Cells
• In this chapter: 1.4 Specialisation in Animal Cells
• In this chapter: 1.5 Specialisation in Plant Cells
• In this chapter: 1.6 Diffusion

Continue in the full course

This lesson is section 1.2 (AGCBH0102) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.