For the IB Biology course

1. Cell
Theory
Stephen Taylor
i-Biology.net
Image: Cells by Filter Forge on Flickr http://flic.kr/p/ePXpR5

2. All living things are made of
C
E
L
L
S
Longitudinal section of a root tip of Maize (Zea mays)
by Science and Plants for Schools on Flickr (CC) http://flic.kr/p/bNNM6M

3. All living things are made of
Unicellular organisms are singlecelled and can carry out all of the
functions of life independently.
Multicellular organisms have
specialized cells to carry out specific
functions.
C
E
L
L
S
Longitudinal section of a root tip of Maize (Zea mays)
by Science and Plants for Schools on Flickr (CC) http://flic.kr/p/bNNM6M

4. C
E
L
L
S
are the smallest
units of
life.
Paramecium multimicronucleatum
by Proyecto Agua on Flickr (CC) http://flic.kr/p/7W7J3y

5. C
E
L
L
S
are the smallest
units of
life.
Specialized
structures within
cells (organelles) carry
out different functions.
Organelles cannot
survive alone.
Paramecium multimicronucleatum
by Proyecto Agua on Flickr (CC) http://flic.kr/p/7W7J3y

6. C come
only
E from
L existing
cells.
L
S
4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS

7. C come
only
E from
L existing
cells.
L
S
Cells multiply through
division.
All life evolved from
simpler ancestors.
Mitosis results in
genetically identical diploid
daughter cells.
Meiosis generates haploid
gametes (sex cells).
Pasteur disproved the
theory of spontaneous
generation with his
experiments.
4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS

9. 1665
Hooke names “cells” in his book
“Micrographia” after observing
cork under a lense.
All living things
are made of cells.
Hooke’s Micrographia in full!
http://lhldigital.lindahall.org/cdm/ref/collection/nat_hist/id/0

10. All living things are
made of cells.
1676
van Leeuwenhoek, a master microscope maker identifies
“animalcules” and becomes the father of microbiology.
http://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek

11. 1833
Robert Brown names the cell nucleus.
Cells are the smallest units of life.
He also discovered Brownian motion:
Robert Brown: http://en.wikipedia.org/wiki/Robert_Brown_(botanist)
http://en.wikipedia.org/wiki/Brownian_motion

12. 1855
Robert Remak discovers cell division and confirms the existence
of the plasma membrane. Cells come only from pre-existing cells.
Robert Remak: http://en.wikipedia.org/wiki/Robert_Remak

13. 1864
Pasteur disproves the prevailing theory of “spontaneous
generation” with his swan-neck flask experiments.
Populations need to be seeded by existing populations: cells come
only from pre-existing cells.
Image from Amoeba Mike’s Blog (go read the original post): http://amoebamike.wordpress.com/2009/10/06/spontaneousgeneration-a-brief-history-of-disproving-it

14. Labeling the parts of the microscope activity:
http://www.biology.ualberta.ca/facilities/multimedia/uploads/intro-biology/microscope.html

15. Magnification
The image we see through
the light microscope has
been magnified.
Objective lens
x eyepiece lens
Image from wikimedia commons: http://commons.wikimedia.org/wiki/File:Microscope-blank.svg

16. Modern Microscopy
Image: d2540-6 by USDA on Flickr (CC): http://flic.kr/p/dPqvvY

17. Modern Microscopy
As we develop more and
more sophisticated and
precise imaging tools, we can
see more detail of the cells
and molecules that make us.
Scanning electron
microscopes deliver highresolution, 3D surface
images of structures,
whereas transmission
electron microscopes give us
a view inside cells and
organelles.
Image: d2540-6 by USDA on Flickr (CC): http://flic.kr/p/dPqvvY

18. Emiliana huxleyi
Image from: http://earthguide.ucsd.edu/earthguide/imagelibrary/emilianiahuxleyi.html

19. Transmission electron micrograph of HIV particles.
120nm
HIV-1. Transmission electron micrograph, via wikimedia commons: http://commons.wikimedia.org/wiki/File%3AHIV1_Transmission_electron_micrograph_AIDS02bbb_lores.jpg

20. Scanning electron micrograph of HIV particles
budding on a human lymphocyte.
1μm
False-coloured scanning electron micrograph of HIV (green) budding on a lymphicoyte (blue)
http://en.wikipedia.org/wiki/File:HIV-budding-Color.jpg OR http://phil.cdc.gov/phil/details.asp?pid=10000

22. Unicellular Organisms
carry out all the functions of life
M ovement
R espiration
S ensitivity
G rowth
R eproduction
E xcretion
N utrition
Paramecium bursaria
by Proyecto Agua on Flickr (CC) http://flic.kr/p/7WXdFz

23. Given the right conditions, cells can
survive outside their normal habitat.
Art from Petri dishes_1 by Image in Science and Art on Flickr (CC) http://flic.kr/p/838xjC

24. VIRUSES
Are they living or non-living?
Hmm…..
Image: Swine Flu H1N1 virus influenza 9.0 by hitthatswitch on Flickr (CC) http://flic.kr/p/74e4SP

25. Some units that I use & know
Unit abbr.
Metric equivalent
kilometer
km
1,000m
1 x 103m
meter
m
1m
1m
centimeter
cm
0.01m
1 x 10-2m
mm
0.001m
1 x 10-3m
millimeter
micrometer
nanometer
μm
nm
write this correctly
0.000 001m
0.000 000 001m
1x
10-6m
1x
10-9m
μm = micrometers
We usually use this in discussion of cells.
There are 1,000μm in one mm.
X 1,000
÷1,000
÷1,000
÷1,000

38. 50μm
Human egg cell, from Gray’s Anatomy (1858). http://commons.wikimedia.org/wiki/Gray%27s_Anatomy_plates

39. 5μm
Human sperm cell, from Gray’s Anatomy (1858). http://commons.wikimedia.org/wiki/Gray%27s_Anatomy_plates

40. Scanning electron micrograph of
human sperm and egg cells.
5μm
Image from wikimedia commons http://en.wikipedia.org/wiki/Spermatozoon

41. Which dissolves faster: sugar
cubes or sugar crystals? Why?
Sugar Cubes by Uwe Hermann on Flickr (CC) http://flic.kr/p/cFMMc

42. What will go cold faster: French
fries or a baked potato? Why?
French Fries by Ian Britton on Flickr (CC) http://flic.kr/p/6RLQ8j

43. Which makes green tea faster: tea leaves or powder?
Matcha Latte by Cupcake Murder Aftermatch on Flickr (CC) http://flic.kr/p/fCkpb5

44. What type of crisps
delivers more
flavour:
regular-cut
or
crinkle-cut?
Why?
Smiths Plain Chips by Penguin Cakes on Flickr (CC) http://flic.kr/p/5ygb8v

45. IN:
 Oxygen
 Nutrients
 Water
The plasma membrane
of a cell is the surface of
exchange for materials
between the inside and
the outside of the cell.
OUT:
 Carbon dioxide
 Waste
 Products (e.g. proteins)
http://commons.wikimedia.org/wiki/Sphere

46. As the cell gets larger, it requires
more resources to be imported and
produces more products (and waste)
to be exported.
Therefore, a larger volume requires
more exchange across the membrane.
http://commons.wikimedia.org/wiki/Sphere

47. As the cell gets larger…
http://commons.wikimedia.org/wiki/Sphere

48. As the cell gets larger…
…the surface area to
volume ratio
actually gets
smaller…
http://commons.wikimedia.org/wiki/Sphere

49. As the cell gets larger…
…the surface area to
volume ratio
actually gets
smaller…
…so the
exchange
processes
become less
efficient with
increasing size.
http://commons.wikimedia.org/wiki/Sphere

50. Diffusion Pathways
are shorter (and
more efficient)
in
with a larger
surface are to
volume ratio.
http://commons.wikimedia.org/wiki/Sphere

53. C
E
L
L
S
D
I
V
I
D
E
Surface are to volume ratio
is a factor that limits the
size of cells.
By dividing to make more,
smaller cells, the efficiency
of the exchange processes
across the membranes (into
and out of the cells) can be
kept high.
Shorter diffusion paths.
More surfaces for reactions.
Removal of heat and waste
4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS

54. Structure/Function
Natural selection favours adaptations that give an advantage.
Folded structures are everywhere in nature, maximising the surface
area to volume ratio for exchange of materials.
Mammalian liver mitochondria: http://commons.wikimedia.org/wiki/File:Mitochondria,_mammalian_lung_-_TEM_(2).jpg

55. Big Cell Exceptions
Caulerpa species of algae are
one giant cell with many
nuclei distributed throughout.
http://en.wikipedia.org/wiki/Caulerpa

56. Big Cell Exceptions
Epulopiscium is a giant
species of bacteria. Read
more about it here:
NotExactlyRocketScience.
E. coli
100μm
Epulpoiscium, by AJ Cann on Flickr (CC) http://flic.kr/p/4Nzq9t

57. Is maximising surface area to volume
ratio always an advantage?
Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/

58. Two Minute Essay
Explain the importance of surface area to
volume ratio as a factor limiting cell size.
Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/

59. Exploration: which cools faster?
Add 30ml hot water to a small cup and to a petri dish.
Predict: Will one cool faster? Why?
Record: Take the temperature of each one every minute.
Describe or plot the results.
30ml
30ml

60. Design an investigation into the effect of SA:Vol ratio on exchange of…

61. Emergent Properties
the whole is
more than the sum
of its parts
Photo by Stephen Taylor: http://www.flickr.com/photos/gurustip/9668701965/in/photostream

65. Stem Cells
A cluster of nascent retinae generated from 3D embryonic stem cell cultures, by UCL News on Flickr (CC): http://flic.kr/p/ffPBPT

66. A Stem Cell Story
http://www.youtube.com/watch?v=2-3J6JGN-_Y

67. Stem Cells retain the capacity to divide and can
differentiate along divergent pathways.
Totipotent
Can differentiate into any type
of cell.
Pluripotent
Can differentiate into many
types of cell.
Multipotent
Can differentiate into a few
closely-related types of cell.
Unipotent
Can regenerate but can only
differentiate into their
associated cell type
(e.g. liver stem cells can only
make liver cells).
Image from: http://en.wikipedia.org/wiki/Stem_cell

68. Stem Cells retain the capacity to divide and can
differentiate along divergent pathways.
By Fwfu at en.wikibooks [Public domain], from Wikimedia Commons
http://commons.wikimedia.org/wiki/File%3AStemcelldifferentiaion.jpg

69. Stem Cells retain the capacity to divide and can
differentiate along divergent pathways.
Screenshot from this excellent tutorial: http://www.ns.umich.edu/stemcells/022706_Intro.html

70. Differentiation (specialization) of cells:
All diploid (body) cells have the same chromosomes.
So they carry all the same genes and alleles.
BUT
Not all genes are expressed (activated) in all cells.
The cell receives a signal.
This signal activates or deactivates genes.
Genes are expressed accordingly and the cell is committed.
Eventually the cell has become specialized to a function.
Key Concept: Structure vs Function
How do the structures of specialized cells reflect their
functions? How does differentiation lead to this?
Screenshot from this excellent tutorial: http://www.ns.umich.edu/stemcells/022706_Intro.html

71. Therapeutic Uses of Stem Cells
Treatment for Leukemia
Problem
Treatment
Chemotherapy and radiotherapy can be used
to destroy the white blood cells, but these
need to be replaced with healthy cells. Bone
marrow transplants are often used for this.
Role of
Stem Cells
From:
Cancer of the blood or bone marrow,
resulting in abnormally high levels of poorlyfunctioning white blood cells.
Hematopoetic Stem Cells (HSCs) can be
harvested from bone marrow, peripheral
blood or umbilical cord blood. As these can
differentiate to form any type of white blood
cell, they can be used to repopulate the bone
marrow and produce new, healthy blood cells.
The use of a patient’s own HSCs means there
is far less risk of immune rejection than with a
traditional bone marrow transplant.
http://en.wikipedia.org/wiki/Pluripotential_hemopoietic_stem_cell
Animation of this process:
Animated tutorials from: http://outreach.mcb.harvard.edu/animations/thera7c.swf

72. Two Minute Essay
What is a stem cell?
How do stem cells differentiate into specialized cells?
Outline one therapeutic use of stem cells.
Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/

75. For more resources & links
including many on Stem Cells.
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