What does the cell unit include? Cell membrane – structure, diffusion and osmosis Cell signaling and the extracellular matrix Cell division – mitosis Cell theory Why are cells small? Microscopes & magnification Stem cells & differentiation Prokaryotic cells – structure and function Eukaryotic cells – structure and function

Outline the cell theory All living things are made of cells. Cells are the smallest unit of life. Existing cells have come from other cells.

Discuss evidence for the cell theory What follows is a historical perspective on how the cell theory developed

What level of complexity is necessary for life? Aristotle (384 – 322BC) Organised material (living) Unorganised material (non-living) Heterogeneous (organs) Homogeneous (tissues) Matter © 2010 Paul Billiet ODWS

What level of complexity is necessary for life? 17th century scientists discovered tissues were made of cells (Hooke 1665 and Leeuwenhoek 1677) Image Credit Cork cells © 2010 Paul Billiet ODWS

Cells 18th and 19th century scientists showed that tissues were made of cells The cells of a particular tissue had a common structure. Image Credit Liver cells

THE CELL THEORY Matthias Schleiden (1838) & Theodor Schwann (1839) “The cell is the basic unit of living tissue” The cell is the smallest unit that can show all the characteristics of life Organelles requires cooperation of other organelles for successful function © 2010 Paul Billiet ODWS

« Omnis cellula e cellula » Rudolf Virchow (1858) noted that: “all cells come from pre-existing cells” Cell division – mitosis or binary fission Suggests that cells have a common ancestor and therefore all organisms are related Image Credit Cell division

9 life processes = MRRREGNTS State that unicellular organisms carry out all the functions of life 9 life processes = MRRREGNTS Name and briefly explain: Nutrition Metabolism Growth Response Excretion Homeostasis Reproduction

Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit – Interesting but not required in new syllabus SI = ??? 1 nm = ? 1 m = ?

Molecules of biological significance are around 1 nm in size where as the cell membrane is about ten times thicker at 10nm. Whereas a virus is ten times larger again at around 100nm. Whereas a bacteria is ten times larger again at around 1 um. Whereas a eukaryotic animal cell is ten times larger again at around 10 um. Whereas a eukaryotic plant cell is ten times larger again at around 100 um. Read through notepacket to see a good description on how to compare cell sizes with each other….

Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification

Growing cells 1µm 2µm 3µm 4µm 5µm 6µm © 2010 Paul Billiet ODWS

Surface Area:Volume Ratio © 2010 Paul Billiet ODWS