1.2.41 · Cell Structure
Prokaryotic v Eukaryotic Cells — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions
5 min read 8 parts Lesson 11 of 13 1 quiz
Lesson summary
1.2.4 Prokaryotic v Eukaryotic Cells — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Describe the structure of prokaryotic cells and compare them with eukaryotic cells.Genetic material — circular DNA free in the cytoplasm, not packaged with proteins.No membrane-boun…
- No membrane-bound organelles
- Organisation
- Pili and flagella
- Microvilli
- Respiration
- Microtubule
Part 1 of 6Features of prokaryotic cells
Genetic material
- Genetic material circular DNA free in the cytoplasm, not packaged with proteins.
No membrane-bound organelles
- No membrane-bound organelles there is no nucleus or mitochondria.
Size
- Size usually 1–5 µm, many times smaller than eukaryotic cells.
Ribosomes
- Ribosomes smaller 70S ribosomes.
Cell wall
- Cell wall made of peptidoglycan.
Organisation
- Organisation always unicellular.
Part 2 of 6Extra prokaryotic structures
Extra prokaryotic structures
Plasmids
- Plasmids small circular DNA molecules in many bacteria.
Capsule
- Capsule a slime layer outside some cell walls.
Pili and flagella
- Pili and flagella attachment and movement.
Part 3 of 6Eukaryotic cell features
Genetic material
- Genetic material linear chromosomes in a nucleus, associated with histone proteins.
Organelles
- Organelles multiple membrane-bound organelles such as a nucleus, mitochondria and chloroplasts.
Ribosomes
- Ribosomes larger 80S ribosomes.
Cell wall
- Cell wall cellulose in plants and chitin in fungi.
Size
- Size up to 100 µm across.
Organisation
- Organisation can form multicellular organisms.
Part 4 of 6Comparison table
| Feature | Prokaryotes | Eukaryotes |
|---|---|---|
| Size | 0.5–5 µm | Up to 100 µm |
| Genetic material | Circular chromosome, no proteins | Linear chromosomes with histones in nucleus |
| Cell division | Binary fission, no spindle | Mitosis or meiosis with spindle fibres |
| Ribosomes | 70S | 80S |
| Organelles | No membrane-bound organelles | Many membrane-bound organelles |
| Cell wall | Peptidoglycan | Cellulose or chitin |
Part 5 of 6More from the specification
More from the specification
Endoplasmic Reticulum and Vesicular Transport
- Rough endoplasmic reticulum synthesizes proteins destined for secretion,
- which bud off in transport vesicles that fuse with the Golgi body for post-translational modification and sorting.
The Golgi Apparatus and Secretion
- The Golgi body modifies proteins and lipids, packaging them into secretory vesicles or lysosomes that travel to the cell surface membrane for exocytosis of substances.
Microvilli and Absorption Surface Area
- In specialized animal epithelial cells,
- such as those lining the small intestine and kidney nephrons, the cell surface membrane folds into microvilli to substantially expand the surface area for rapid absorption of nutrients.
Non-Cellular Viruses vs. Living Animal and Bacterial Cells
- Viruses are acellular infectious entities lacking metabolic machinery, cytoplasm,
- and organelles;
- unlike living animal cells that generate metabolic energy via cellular respiration, viruses replicate only within host cells.
Endoplasmic Reticulum and Vesicular Transport
- Rough endoplasmic reticulum synthesizes proteins destined for secretion,
- which bud off in transport vesicles that fuse with the Golgi body for post-translational modification and sorting.
The Golgi Apparatus and Secretion
- The Golgi body modifies proteins and lipids, packaging them into secretory vesicles or lysosomes that travel to the cell surface membrane for exocytosis of substances.
Microvilli and Absorption Surface Area
- In specialized animal epithelial cells,
- such as those lining the small intestine and kidney nephrons, the cell surface membrane folds into microvilli to substantially expand the surface area for rapid absorption of nutrients.
Non-Cellular Viruses vs. Living Animal and Bacterial Cells
- Viruses are acellular infectious entities lacking metabolic machinery, cytoplasm,
- and organelles;
- unlike living animal cells that generate metabolic energy via cellular respiration, viruses replicate only within host cells.
Centriole
- A microtubule structure organising the spindle in animal cells.
Animal cell
- A cell with a nucleus, cytoplasm, cell membrane and mitochondria but no cell wall, chloroplasts or large vacuole.
Endoplasmic reticulum
- Rough and smooth (lipids, detoxification).
- (ribosomes, proteins)
Nuclear envelope
- The double membrane around the nucleus, with pores.
Electron micrograph
- A photograph taken through an electron microscope.
Aerobic respiration
- Respiration that uses oxygen to release a relatively large amount of energy.
Permanent vacuole
- Sap-filled space that keeps a plant cell firm.
Vesicle
- A small membrane-bound sac that moves materials within a cell or to the plasma membrane.
Microvilli
- Tiny folds on the surface of villus cells.
Respiration
- Chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
Microtubule
- Hollow protein filament used for support and transport.
Vacuole
- Membrane-bound store; the plant central vacuole maintains turgor.
Micrograph
- A photograph taken through a microscope.
Part 6 of 6More on this topic
- Organisation
- prokaryotes are always unicellular, whereas eukaryotes can be multicellular.
Key terms
| Term | Meaning |
|---|---|
| Prokaryote | A cell with no nucleus and no membrane-bound organelles. |
| Eukaryote | A cell with a nucleus and membrane-bound organelles. |
| Peptidoglycan | The cell wall material of bacteria. |
| Binary fission | Division of a prokaryotic cell into two without a spindle. |
| Plasmid | A small circular DNA molecule in bacteria. |
| 70S ribosome | The smaller ribosome type in prokaryotes, mitochondria and chloroplasts. |
Avoid these mistakes
1
Saying prokaryotes have no DNA — they have DNA that is not in a nucleus.
2
Saying all cell walls contain cellulose — bacteria use peptidoglycan.
3
Saying prokaryotes divide by mitosis — they divide by binary fission.
4
Saying mitochondria are prokaryotic cells — they are organelles with 70S ribosomes.
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