1. 1.5 The origin of cells September 4th
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3. EQ: How do we know how life began?

4. 1.5.1 Cells can only be formed by the division of pre existing cells
Louis Pasteur made a nutrient broth by boiling water containing yeast and sugar
Swan-necked flask
Omne vivum ex vivo (All life from life)

5. 1.5.2 The first cells must have arisen from non-living material

6. 1.5.2 Recipe for the origin of life
The synthesis of simple organic molecules (amino acids) from inorganic molecules (water, carbon dioxide, ammonia)
The assembly of these molecules into polymers (e.g. polypeptides from amino acids)
Formation of polymers that can self-replicate to allow for inheritance of characteristics
Development of membranes with internal chemistry different from their surroundings

7. 1.1.2 Cells carry out all functions necessary for life
growth: an irreversible increase in size
homeostasis: keeping conditions inside the organisms within tolerable limits
metabolism: chemical reactions inside the cell, including cell respiration to release energy
nutrition: obtaining food, to provide energy and the materials needed for growth
reproduction: producing offspring either sexually or asexually
sensitivity: perceiving and responding to changes in the environment
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8. The cell theory All living things are made of one or more cells
The cell is the smallest unit of life
All cells come from pre-existing cells

9. Limitations to the cell theory
Striated muscle fibers: multi-nucleated, long (30 mm)
Fungal hyphae: multi-nucleated
Giant algae (Acetublaria): large (100 mm)
Viruses: living or not?

10. 2. What is the evidence for the cell theory?
All living things are made of one or more cells
microscopes allow us to observe that all living things are either unicellular or multicellular
Robert Hooke: pioneering microscopist, cork cell
Antonio Van Leeuwenhook: master lens maker, animacules

11. 2. What is the evidence for the cell theory?
The cell is the smallest unit of life
nothing smaller than a cell can survive independently
subcellular structures cannot survive independently (nuclei, ER, golgi, chloroplasts, mitochondria)
the lower limit on cell size is about 200nm, large enough for DNA, ribosomes, and membranes

12. Why do cells look so different?
Stem cells = Cells that retain capacity to divide and differentiate along different pathways

13. Why do cells look so different?
multicellular organisms can differentiate into a variety of interdependent cell types
each specialized to carry out a subset of functions  greater efficiency
cellular differentiation
achieved through differential gene expression
all cells in an organism have identical DNA

14. 4. Relative sizes of cells
molecules: ~ 1 nm
cell membrane thickness: ~ 10 nm
viruses: ~ 100 nm
bacteria: ~ 1 µm
organelles: up to 10 µm
eukaryotic cells: up to 100 µm

16. Cell size molecules: ~ 1 nm cell membrane thickness: ~ 10 nm
viruses: ~ 100 nm
bacteria: ~ 1 µm
organelles: up to 10 µm
eukaryotic cells: up to 100 µm

17. Why is the cell small?

18. Why is the cell small? Surface area determines rate of exchange
Volume determines metabolism
As cell size increases, volume increases proportionally faster than SA => SA: V ratio decreases
Low SA reduces rate of exchange while high V increases metabolic demands
Cell cannot meet needs of metabolic demands

19. Cell size
Stephen Taylor (i-biology)

21. Stephen Taylor (i-biology)

22. Stephen Taylor (i-biology)

23. Stephen Taylor (i-biology)

24. Stephen Taylor (i-biology)

25. Stephen Taylor (i-biology)

26. Stephen Taylor (i-biology)

31. Science of perception: Law of closure

32. ATM, floppy disk, hard drive

34. 1.7 Systems biologists “Whole is greater than the sum of its parts”
Put together the parts that make up a system and then observe the properties of that 'emerge' from the system
“Emergent properties”: occurrence of unexpected characteristics or properties in a complex system
Reductionism = reduce phenomenon to its constituent parts.
Smallest parts are predictable then the system as a whole is predictable.
No new properties will arise from the sum of the parts

35. What do the components of the watch do individually?
What do they do when they are put together in the right way?
William Paley: Complexity of X necessitates a designer (as a watch)