2.1++Cell+theory

2 Cells - 2.1 Cell theory - 2.2 Prokaryotic cells - 2.3 Eukaryotic cells - 2.4 Membranes - 2.5 Cell division - Cell Labs

2.1 Cell theory

 * Assessment statements** (IBO notes included to clearly indicate what needs to be understood and what does not)
 * || Assessment statement || notes ||
 * 2.1.1 || Outline the cell theory. || Include the following: Living organisms are composed of cells. Cells are the smallest unit of life. Cells come from pre-existing cells. ||
 * 2.1.2 || Discuss the evidence for the cell theory. ||  ||
 * 2.1.3 || State that unicellular organisms carry out all the functions of life. || Include metabolism, response, homeostasis, growth, reproduction and nutrition. ||
 * 2.1.4 || Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit. || Appreciation of relative size is required, such as molecules (1 nm), thickness of membranes (10 nm), viruses (100 nm), bacteria (1 µm), organelles (up to 10 µm), and most cells (up to 100 µm). The three-dimensional nature/shape of cells should be emphasized. ||
 * 2.1.5 || Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification. || Magnification could be stated (for example, ×250) or indicated by means of a scale bar. ||
 * 2.1.6 || Explain the importance of the surface area to volume ratio as a factor limiting cell size. || Mention the concept that the rate of heat production/waste production/resource consumption of a cell is a function of its volume, whereas the rate of exchange of materials and energy (heat) is a function of its surface area. Simple mathematical models involving cubes and the changes in the ratio that occur as the sides increase by one unit could be compared. ||
 * 2.1.7 || State that multicellular organisms show emergent properties. || Emergent properties arise from the interaction of component parts: the whole is greater than the sum of its parts. ||
 * 2.1.8 |||| Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. ||
 * 2.1.9 || State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. ||  ||
 * 2.1.10 || Outline one therapeutic use of stem cells. || This is an area of rapid development ||

A good first step to understanding cell theory and what cells really are is watching the BBC Documentary [|The Cell]
 * First Steps**

For Cell Theory use the [|Essential Biology] notes from[| i-Biology] instead. I think it is better structured and more focused for this topic.
 * Workbooks and Worksheets**

The [|i-Biology] presentation brings together the whole topic in this one resource media type="custom" key="23679964"
 * Presentations and Tutorials**

Jason De Nys also has a very good presentation to use for note development media type="custom" key="24508062"

Cell Theory is often misunderstood by students John Burrell ([|click4biology]) summarises the topic well here media type="custom" key="23681292"

Evidence for cell theory is often a focus of exam questions that is addressed by him in this video media type="custom" key="23681332" ‪

All the remaining assessment statements are addressed by John Burrell ([|click4biology]) too [|2.1.3 Unicellular Organisms‬] ‪[|2.1.4 Sizes of cells‬] ‪[|2.1.5 Magnification]‬ ‪[|2.1.6 Surface area-volume ratios limiting cell size]‬ - This is a key concept and will be used time and again throughout the course ‪[|2.1.7 Emergence‬] ‪[|2.1.8 Differentiation and Specialisation‬]

Stem cells is also first addressed at this point. We will revisit it again in later topics. This [|Khan Academy video] talks about embryonic stem cells (there are other types to). An animated alternative is the narrated tutorial from [|Sunamas inc.] which explains what embryonic stem cells are, how they can be harvested and potentially used.

Potential and realised stem cell therapies are outlined in this HHMI slideshow (click on the image to view the slideshow)

Look to the [|i-Biology] resource for a overall view of stem cells. Be aware that this is a rapidly growing area of human knowledge and stem cell therapy in particular will change quickly.

The university of Utah has great resources here a fun link shows the [|scale of cells] and their components. You can also learn about [|cell evolution] too
 * Useful links**

This BBC article discusses recent devlopment in the use of cloning to produce human embryonic stem cells. It is very good at discussing the ethical uses surrounding the use of human embryonic stem cells.