Unit Overview
Cell Structure
CIE A-Level BiologyΒ· 5 min read π n/a
1. Unit at a glance
This unit follows a logical sequence: we start with how biologists see and measure cells, before diving into the detailed structure of each major type of biological entity. You will first learn about eukaryotic cells (the complex cells that make up plants and animals), then simpler prokaryotic cells, then acellular viruses, before finishing with a direct comparison of the two main cell types.
Mastery of this unit is critical: all later topics from cell division to immunology to physiology rely on understanding cell structure and function.
This unit covers the following core sub-topics:
Microscopy and cell measurement
Learn how light and electron microscopes work, and master calculations for magnification, image size and actual size.
β β β± 10 min
Eukaryotic cell ultrastructure
Explore the structure and function of all major membrane-bound and non-membrane-bound organelles in plant and animal cells.
β β β β± 15 min
Prokaryotic cell structure
Understand the key structural features of bacterial prokaryotic cells.
β β β± 10 min
Virus structure
Learn the acellular structure of viruses, including their core common components.
β β β± 8 min
Comparison of eukaryotic and prokaryotic cells
Summarize key structural similarities and differences between eukaryotic and prokaryotic cells.
β β β β± 10 min
2. Common Pitfalls
Wrong move:
Confusing magnification and resolution
Why:
Students often mix these two distinct properties of microscopes, which is a common exam question trap
Correct move:
Remember: magnification makes an image larger, resolution is the ability to distinguish two separate points as distinct
Wrong move:
Classifying viruses as prokaryotic cells
Why:
Viruses are non-cellular, so they do not fit into the prokaryote/eukaryote classification
Correct move:
Always categorize viruses as acellular infectious particles, not prokaryotic cells
Wrong move:
Forgetting that prokaryotes have ribosomes
Why:
Students often assume prokaryotes have no organelles at all, but ribosomes are present
Correct move:
Remember prokaryotes have small 70S ribosomes, which are not membrane-bound
3. Quick Reference Cheatsheet
Concept / Formula | Key Detail | ||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Magnification formula | |||||||||||||||||||||||||||||||||||
Resolution | Ability to distinguish two separate adjacent points as distinct | ||||||||||||||||||||||||||||||||||
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