1. Cells
Lectures #4 & #5, Chapter 4
by John Cozza, Biology Dept.
(some material modified from Raven, Biology 9th
ed.)

2. Cells outline
• What is a cell?
• Types of cells
• Cytoplasm
– Cytosol
– Organelles
– Cytoskeleton
• Cell wall and ECM
– Cell junctions

3. Cells outline
• What is a cell?
• Types of cells
• Cytoplasm
– Cytosol
– Organelles
– Cytoskeleton
• Cell wall and ECM
– Cell junctions

4. What is a cell?

5. How did the first cell originate?
• Genetics first:
RNA world
• Metabolism first
• Proteins first
• Membrane first
• Hybrid world
• Intelligent design?
http://pandasthumb.org/archives/2010/02/primordial-soup-1.html

6. Interactive question #1
Intelligent design
is not a scientific
hypothesis
because it is not
A.an educated
guess
B.possible
C.controversial
D.testable

7. One
hypothesis of
life’s origin…
• Micro-caves of
undersea
volcanic vents
• Metabolism first
• Then RNA
• Then proteins
• Then DNA

8. …and the first
prokaryotic
cells
(bacteria &
archaea)
• Then lipids &
membranes
• Then cell walls
Martin, W. and M. Russell 2003. On the
origins of cells: a hypothesis for the
evolutionary transitions from abiotic
geochemistry to chemoautotrophic
prokaryotes, and from prokaryotes to
nucleated cells. Phil. Trans. R. Soc.
Lond. B 358: 59–85.

9. Cell size

10. Cells outline
• What is a cell?
• Types of cells
• Cytoplasm
– Cytosol
– Organelles
– Cytoskeleton
• Cell wall and ECM
– Cell junctions

11. Types of cells
Prokaryotic
Eukaryotic

12. Prokaryotic cell
http://classes.midlandstech.com/carterp/Courses/bio225/chap04/sld003.htm

13. Nitrosomonas sp. (Proteobacteria)
Dirtland: http://commtechlab.msu.edu/sites/dlc-me/zoo/zdrs0232.html
Anabaena variabilis
(Cyanobacteria)
http://genome.jgi-psf.org/anava/anava.home.html
Some prokaryotes have internal
membranes!

14. Prokaryotic cell
E. coli
By David Goodsell
Scripps Institute

15. Yellow = DNA, RNA, & proteins
Blue = Cytoplasmic proteins
Purple = ribosomes
Green = membranes + proteins
http://mgl.scripps.edu/people/goodsell/illustration/public

16. TEM of eukaryotic cell
http://www2.estrellamountain.edu/faculty/farabee/BIOBK/biobookcell2.html

17. Eukaryotic cell
Prokaryotic
cell

18. Interactive question #2
The definitive difference
between prokaryotic
and eukaryotic cells is
that prokaryotes
A.are smaller
B.are pathogens
C.do not have a nucleus
D.have a cell wall
E.lack internal
membranes

19. Eukaryotic cell section
Yellow & green = cell
membrane and proteins
Blue = proteins
Blue filaments =
cytoskeleton
Pink = ribosomes
Tan = mRNA, tRNA
From: Inside a
Eukaryotic Cell
by David Goodsell
Scripps Institute
http://mgl.scripps.edu/peop
le/goodsell/gallery/patterso
n.html

20. Eukaryotic cell section
Yellow (L) = Golgi apparatus
Yellow (R) = mitochondrion
Blue = proteins
Green = glycosylation
Blue “Buckyball” = coated vesicle
Pink = ribosomes
Tan = mRNA, tRNA

21. Eukaryotic cell section
Yellow = nuclear membrane
Blue = proteins
Orange “spaghetti” = mRNA being
synthesized (R) and then spliced in
nuclear pore (L)
Pink (R) = DNA

22. Origin of eukaryotic cell:
endosymbiosis
fermentation
photosynthesis
respiration

23. Origin of the nucleus:
alternative hypotheses
Martin, W. 2005.
Archaebacteria
(Archaea) and the
origin of the
eukaryotic nucleus.
Current opinion in
microbiology 8(6):
630-637.

24. Origin of the nucleus:
alternative hypothesis
Margulis, L. 2000.
The chimeric
eukaryote: Origin
of the nucleus from
the karyomastigont
in amitochondriate
protists. PNAS
97(13): 6954-6959

25. According to the various
hypotheses, the nucleus
may have evolved from
any of the following
except:
A.A merger of a
community of cells
B.A merger of a liposome
and a chromosome
C.A spore
D.An engulfed cell
E.Infoldings of the cell
Interactive
question #3

26. Cells outline
• What is a cell?
• Types of cells
• Cytoplasm
– Cytosol
– Organelles
– Cytoskeleton
• Cell wall and ECM
– Cell junctions

27. Cytosol
• Water (~70%)
• Ions
• Building blocks ,
nutrients, etc.
• Proteins (>20%)
• Other
macromolecules
• DNA (prokaryotes)
http://en.wikipedia.org/wiki/Cytosol
http://www.scripps.edu/news/scientificreports/sr2008/mb08olson.html

28. Cytosol:
E. coli
by David
Goodsell
The
Machinery
of LIfe
Fig. 4.3

29. Think—pair—share
What are the
advantages to
a eukaryotic
cell of having
organelles?

30. Organelles (with membrane)
Organelle Main features Function
Nucleus
Endoplasmic
reticulum (ER)
Golgi apparatus
Mitochondrion
Chloroplast
Storage plastid
Vacuole
Lysosome
Microbody

31. Nucleus and endomembrane system
Why are we
considering
them
together?
White blood
cell
by David Goodsell
The Machinery of LIfe
Fig. 5.3

32. Nuclear pore
by David Goodsell
The Machinery of Life, Fig. 5.3

33. Endoplasmic reticulum
(rough ER)
by David Goodsell
The Machinery of Life, Fig. 5.4

34. Golgi apparatus
by David Goodsell
The Machinery of Life, Fig. 5.4

35. Secretory vesicles
leaving the cell
by David Goodsell
The Machinery of Life, Fig. 5.6

36. Energy organelles
• Mitochondria
(red)
• Chloroplast
(deep green)
Euglena gracilis

37. Mitochondrion
by David Goodsell
The Machinery of Life, Fig. 5.1

38. Artemesia
chloroplast
TEM
by George
Chapman
Chloroplast

39. Artemesia
chloroplast
TEM
by George
Chapman
Chloroplast
internal
membranes
by David Goodsell
http://cbm.msoe.edu/markMyweb/SUN-
chlorophyllEbookWorking/chloroplast.html
Chloroplast

40. Storage plastids
Cazzonelli, C. &
Pogson, B. 2010.
Source to sink:
regulation of
carotenoid
biosynthesis in
plants. Trends in
plant science
15(5): 266-274.

41. Plastids may
function in all of
the following
except
A.photosynthesis
B.fruit ripening
C.food storage
D.cell respiration
Interactive question #4

42. Vacuole
http://a
mit1b.w
ordpress.
com/the-
molecule
s-of-
life/10-
the-
living-
cell-
gallery/

43. “Organelles” with no membrane
aka macromolecular assemblies
“Organelle” Location Main
features
Function
Pyruvate
dehydrogenase
complex
Replisome
(DNA polymerase)
RNA polymerase
Spliceosome
Ribosome
Fill this table out as we go along…

44. Ribosome
• rRNAs
• Proteins

45. Prokaryotic vs. eukaryotic ribosomes
Melnikov, S.
et al. 2012.
One core,
two shells:
bacterial and
eukaryotic
ribosomes.
Nature
Structural &
Molecular
Biology,
19(6), 560-
567.
Blue = rRNA
Red = protein
Light = conserved
Dark = unique

46. Eukaryote
cytoskeleton
• Microtubules
• Intermediate
filaments
• Actin filaments
(microfilaments)
• Motor proteins
Modified from David Goodsell
The Machinery of Life, Fig. 5.6

47. Bacterial cytoskeleton!
The bacterial cytoskeleton. The only cytoskeletal element present in spherical bacteria such as S. aureus (top left) is the tubulin-
like cell division protein FtsZ (green), which localizes in a ring at the onset of cell division, recruits other cell division proteins, and
defines the division plane. Most rod-shaped bacteria (top right) also contain one or more actin-like MreB homologues (red),
which exhibit helix-like localization patterns and are essential for cell width control. At the onset of cell division, the FtsZ ring
forms and defines the division plane. C. crescentus, a vibrioid bacterium (bottom), contains a third cytoskeletal element, the
intermediate filament-like crescentin (blue), which is required for cell curvature and localizes at the inner curvature of cells.
Cabeen, M. &
Jacobs-Wagner, C.
2007. Skin and
bones: the bacterial
cytoskeleton, cell
wall, and cell
morphogenesis.
The Journal of cell
biology, 179(3):
381-387.

48. Flagella
Bacteria
Eukaryotes

49. Cells outline
• What is a cell?
• Types of cells
• Cytoplasm
– Cytosol
– Organelles
– Cytoskeleton
• Cell wall and ECM
– Cell junctions

50. Bacterial ↑
Plant →
FungalCell walls:
not a wall—a mesh

51. Extracellular matrix: animals
↑ Human
connective
tissue with
fibroblasts
(darker)

52. Cell junctions: animals

53. Plasmodesmata: plants
http://www.mhhe.com/biosci/pae/bota
ny/crang/vtphloem/sieve1/mg0700.html

54. Interactive question #5
Plasmodesmata are
most like which cell
junction in animals?
A.Tight junction
B.Desmosome
C.Gap junction

55. Cells outline
• What is a cell?
• Types of cells
• Cytoplasm
• Cell wall and ECM
Next:
• Membranes