3.1.3Unit 3: Practical Skills in Biology I
Eukaryotic Cells — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 4 parts Lesson 5 of 27 Unit quiz
Part 1 of 4Organelles Common to Animal and Plant Cells
Eukaryotic cells are 10–100 μm across and have a nucleus and other membrane-bound organelles, unlike prokaryotic cells which are much smaller.
Cell surface membrane
- A partially permeable phospholipid bilayer that controls the movement of materials into and out of the cell.
Nucleus
- Surrounded by a double membrane called the nuclear envelope with pores, it contains DNA and controls the activity of the cell.
Nucleolus
- A dense region inside the nucleus where ribosomal RNA is made and ribosomes begin to be assembled.
Mitochondria
- Surrounded by a double membrane with folded cristae, they are the site of aerobic respiration and make ATP.
Ribosomes
- The 80S ribosomes in eukaryotes are the site of translation, and are free in the cytoplasm or attached to the RER.
Endoplasmic reticulum
- The rough ER has ribosomes and makes proteins, while the smooth ER makes and transports lipids.
Part 2 of 4Other Organelles
Other Organelles
Golgi apparatus
- A stack of flattened sacs that modifies, packages and sorts proteins, and sends them off in vesicles.
Lysosomes
- Vesicles from the Golgi containing hydrolytic enzymes, which break down worn-out organelles and engulfed material.
Centrioles
- Found in animal cells, they help to organise the spindle fibres during nuclear division.
Microvilli
- Folds of the cell surface membrane in some animal cells, which increase the surface area for absorption.
Part 3 of 4Plant Cell Features
1
Plant cells have a cellulose cell wall outside the cell surface membrane, which gives support and prevents bursting.
2
A large permanent vacuole is surrounded by a membrane called the tonoplast and contains cell sap, which helps to keep the cell turgid.
3
Chloroplasts have a double membrane and contain chlorophyll in stacked thylakoids, where photosynthesis takes place.
4
Plant cells do not contain centrioles, whereas animal cells do.
5
Both cell types have a nucleus and 80S ribosomes, so they are both examples of eukaryotic cells.
| Feature | Animal cell | Plant cell |
|---|---|---|
| Cell wall | Absent | Cellulose |
| Large permanent vacuole | Absent | Present |
| Chloroplasts | Absent | Present |
| Centrioles | Present | Absent |
Part 4 of 4Exam Checklist & Tips
3.1.3 – Key Points for the Exam
- Nucleus: The organelle that contains DNA and is surrounded by a nuclear envelope.
- Mitochondrion: The organelle where aerobic respiration takes place.
- Golgi apparatus: The organelle that modifies and packages proteins.
- Vacuole: A fluid-filled sac, large and permanent in plant cells.
- Chloroplast: The organelle in which photosynthesis occurs.
- Ribosome (80S): The larger type of ribosome in eukaryotic cells,
- where proteins are made by translation, found free or on the rough endoplasmic reticulum.
Common Mistakes
- Saying that mitochondria make energy, when they release energy by making ATP in respiration.
- Stating that animal cells have no vacuoles at all, when they have only small temporary ones.
- Writing that the cell wall is the same thing as the cell surface membrane.
- Mixing up the nucleolus, which makes ribosomal RNA, with the nucleus.
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Cambridge 9700 AS Biology
Core Formula
Magnification Triangle & Unit Conversion
Formula: M = I / A ⇔ A = I / M ⇔ I = M × A
Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.