Choose an exam and explore concepts through visual explanations, topic maps and revision checks. Open the full chapter notes whenever you need more detail.
THE VISUAL LEARNING STUDIO
See the idea. Understand the connection.
35 visual explanations across 29 chapters, with topic maps throughout the library.
The chapter index will grow as additional notes are prepared. Chapters shown here are a learning collection, not a claim that the entire exam syllabus is complete.
SEE IT. CONNECT IT. EXPLAIN IT.
Understand the chapter visually
2 visual explanations · Study the connections, then test yourself.
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COMPARE & CONNECT
Three osmotic situations
1
Hypotonic outside
Net water entry into the cell; an animal cell may swell and lyse.
2
Isotonic outside
No net water movement; water still moves in both directions.
3
Hypertonic outside
Net water exit; animal cells shrink and plant cells may plasmolyse.
The connection Compare the effective concentrations of non-penetrating solutes across a selectively permeable membrane. This is a simplified school-level model.
Exam trap Isotonic does not mean that water molecules stop moving.
Which condition can produce plasmolysis in a plant cell?
A sufficiently hypertonic external solution causes net water loss and separation of the protoplast from the wall.
LABELLED SCHEMATIC
Inside a eukaryotic cell
1
Plasma membrane
Selectively controls movement across the cell boundary.
2
Nucleus
Contains most of the cell’s DNA; the nucleolus contributes to ribosome assembly.
3
Mitochondrion
Supports aerobic ATP production; it is not the only site where ATP is formed.
4
Rough ER
Membranes with bound ribosomes involved in secreted and membrane proteins.
5
Golgi apparatus
Modifies, sorts and packages cell products.
6
Cytoplasm
Includes cytosol and cellular structures outside the nucleus.
The connection Read this as a simplified animal-cell schematic, not a scale drawing. Plant cells also have a cell wall, plastids and a large central vacuole.
Exam trap Prokaryotes lack a membrane-bound nucleus but still contain DNA and ribosomes.
Does a bacterium lack genetic material because it has no nucleus?
No. Its DNA is present in a nucleoid region, without a nuclear envelope.
Study the expanded notes and the credited detailed textbook lessons. The current chapter index covers core topics; it is not a claim of exhaustive coverage of every examination syllabus. Check the official syllabus and primary references.
The Cell — lesson overview
The cell as a basic unit
The cell is the fundamental structural and functional unit of living organisms. Some organisms consist of one cell; multicellular organisms organise specialised cells into higher levels.
The plasma membrane separates the cell’s contents from its surroundings and selectively regulates exchanges. It is a dynamic structure with lipids and proteins, not a rigid solid wall.
A cell wall is distinct from the plasma membrane. Plant walls are mainly associated with cellulose; bacterial walls generally contain peptidoglycan, with important exceptions among prokaryotes.
Prokaryotic and eukaryotic organisation
Prokaryotic cells lack a membrane-bound nucleus and the typical membrane-bound organelles of eukaryotes. Their genetic material occurs in a nucleoid region.
Eukaryotic cells have a membrane-bound nucleus and compartmentalised organelles. Both prokaryotic and eukaryotic cells possess a plasma membrane, genetic material, cytoplasm, and ribosomes.
A nucleolus is a nuclear region associated with ribosomal RNA production and ribosome-subunit assembly. It is not the same as the nucleus or a separate membrane-bound organelle.
Organelles and function
Mitochondria support aerobic energy metabolism; they do not “create” energy from nothing. Chloroplasts contain the photosynthetic machinery in photosynthetic plant cells and algae.
Rough endoplasmic reticulum bears ribosomes and is important in production of many secreted and membrane proteins. Smooth ER has roles including lipid synthesis, depending on cell type.
The Golgi apparatus modifies, sorts, and packages cellular products. It does not replace ribosomes as the machinery that translates proteins.
