Topic 1: Cell Biology - 15hs

1.1. Introduction to cells

Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. (3.1)

Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5)


Cosmic eye – Video

Cell size and scale – Learn Genetics

International Mindedness

Try with this interesting debate tool by Learn Genetics – The Stem Cell Debate: Is it Over?


• According to the cell theory, living organisms are composed of cells.

The wacky history of cell theory TedEd

• Organisms consisting of only one cell carry out all functions of life in that cell.

• Surface area to volume ratio is important in the limitation of cell size.

Why are cells small?

• Multicellular organisms have properties that emerge from the interaction of their cellular components.

• Specialized tissues can develop by cell differentiation in multicellular organisms.


• Differentiation involves the expression of some genes and not others in a cell’s genome.

• The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.

What are stem cells? TedEd

Applications and Skills

• Application: Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.

• Application: Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.

• Application: Use of stem cells to treat Stargardt’s disease and one other named condition.

• Application: Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues.

• Skill: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells.

Cells alive!

Virtual microscope by Bi


Microscope Simulation by Labster

Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)

Go virtual 

1.2 Ultrastructure of cells

Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)


What if you could make your own cell?

International Mindedness

Microscopes were invented simultaneously in different parts of the world at a time when information travelled slowly. Modern-day communications have allowed for improvements in the ability to collaborate, enriching scientific endeavour.

The Foldscope by Manu Prakash

Theory of Knowledge TOK

The world that we inhabit is limited by the world that we see. Is there any distinction to be drawn between knowledge claims dependent upon observations made by sense perception and knowledge claims dependent upon observations assisted by technology?



• Prokaryotes have a simple cell structure without compartmentalization.

Bacterial cell animation by CellsAlive!

• Eukaryotes have a compartmentalized cell structure.

Eukaryopolis by CrashCourse

Play the cell game Link

• Electron microscopes have a much higher resolution than light microscopes.

Explore samples with this Electronic microscope simulator 

Applications and skills

• Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf.

• Application: Prokaryotes divide by binary fission.

• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
• Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells.

Virtual microscope by BioNetwork

Microscope Simulation by Labster

1.3 Membrane structure

Using models as representations of the real world—there are alternative models of membrane structure. (1.11)
Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9)


• Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules.

• Membrane proteins are diverse in terms of structure, position in the membrane and function.

• Cholesterol is a component of animal cell membranes.

Animation of the cell membrane

Construction of a cell membrane by Wisc online

Membrane formation interactive by NetLogo

Applications and skills

• Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.

• Skill: Drawing of the fluid mosaic model.

Khan Academy video

• Skill: Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model.

• Skill: Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model.

1.4 Transport through membrane

Experimental design—accurate quantitative measurement in osmosis experiments are essential. (3.1)


• Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.

• The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.

Cell membrane trasport interactive

Applications and Skills

• Application: Structure and function of sodium–potassium pumps for active transport and potassium channels for facilitated diffusion in axons.
• Application: Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.
• Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)


Kidney dialysis artificially mimics the function of the human kidney by using appropriate membranes and diffusion gradients.

Kidney diseade video

Printing a Human Kidney TedX

1.5 The origin of cells

Testing the general principles that underlie the natural world—the principle that cells only come from pre-existing cells needs to be verified. (1.9)

Theory of Knowledge

Biology is the study of life, yet life is an emergent property. Under what circumstances is a systems approach productive in biology and under what circumstances is a reductionist approach more appropriate? How do scientists decide between competing approaches?

The origin of complex life

How did life begin?


• Cells can only be formed by division of pre-existing cells.

• The first cells must have arisen from non-living material.

The evolution of the cell by Learn.genetics

• The origin of eukaryotic cells can be explained by the endosymbiotic theory.

Endosymbiotic theory by Glecoe

Applications and skills

• Application: Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth.

Interactive Pasteur Experiment by Pearson

Interactive Pasteur experiment by DK

1.6 Cell division

Serendipity and scientific discoveries—the discovery of cyclins was accidental. (1.4)

Theory of knowledge

A number of scientific discoveries are claimed to be incidental or serendipitous. To what extent might some of these scientific discoveries be the result of intuition rather than luck?

The dicovery of cyclins

Interview with Tim Hunt

Science and serendipity: famous accidental discoveries

The story of serendipity

International Mindedness

Biologists in laboratories throughout the world are researching into the causes and treatment of cancer.

Why is it so hard to find a cure for cancer? TedED

Why do cancer cells behave differently than normal cells? TedED


• Mitosis is division of the nucleus into two genetically identical daughter nuclei.

• Chromosomes condense by supercoiling during mitosis.

• Cytokinesis occurs after mitosis and is different in plant and animal cells.

• Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.

Mitosis animation by CellsAlive!

Cell division interactive by PBSMedia

Cell cycle by Wisc

• Cyclins are involved in the control of the cell cycle.

Control of the cell cycle game 

• Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

Animated Introduction to Cancer Biology by CancerQuest

Mutagens and carcinogens by KhanAcademy

Applications and skills

• Application: The correlation between smoking and incidence of cancers.

The Study That Helped Spur the U.S. Stop-Smoking Movement

• Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.

• Skill: Determination of a mitotic index from a micrograph.

Virtual lab by Glencoe


The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy.

Interactive tumour development by NetLogo

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