1. Tour of the Cell 1 (Ch. 6)

2. Dead White Men Who Discovered (and were made of) Cells:
Anton Van Leeuwenhoek
Robert Hooke

3. Where the Magic Happened

4. Microscopy is certainly a Perspective Changer (sorry in advance)

5. Brightfield (unstained specimen).
Light Microscopy
TECHNIQUE
RESULTS
Brightfield (unstained specimen).
Passes light directly through specimen.
Unless cell is naturally pigmented or
artificially stained, image has little
contrast. [Parts (a)–(d) show a
human cheek epithelial cell.]
(a)
Brightfield (stained specimen). Staining
with various dyes enhances contrast, but
most staining procedures require that cells
be fixed (preserved).
(b)
Phase-contrast. Enhances contrast
in unstained cells by amplifying
variations in density within specimen;
especially useful for examining living,
unpigmented cells.
(c)
50 µm

6. Differential-interference-contrast (Nomarski).
Like phase-contrast microscopy, it uses optical
modifications to exaggerate differences in
density, making the image appear almost 3D.
Fluorescence. Shows the locations of specific
molecules in the cell by tagging the molecules
with fluorescent dyes or antibodies. These
fluorescent substances absorb ultraviolet
radiation and emit visible light, as shown
here in a cell from an artery.
Confocal. Uses lasers and special optics for
“optical sectioning” of fluorescently-stained
specimens. Only a single plane of focus is
illuminated; out-of-focus fluorescence above
and below the plane is subtracted by a computer.
A sharp image results, as seen in stained nervous
tissue (top), where nerve cells are green, support
cells are red, and regions of overlap are yellow. A
standard fluorescence micrograph (bottom) of this
relatively thick tissue is blurry.
50 µm
(d)
(e)
(f)

7. Scanning electron micro- Transmission electron micro-
Electron Microscopy
TECHNIQUE
RESULTS
Scanning electron micro-
scopy (SEM). Micrographs taken
with a scanning electron micro-
scope show a 3D image of the
surface of a specimen. This SEM
shows the surface of a cell from a
rabbit trachea (windpipe) covered
with motile organelles called cilia.
Beating of the cilia helps move
inhaled debris upward toward
the throat.
(a)
Transmission electron micro-
scopy (TEM). A transmission electron
microscope profiles a thin section of a
specimen. Here we see a section through
a tracheal cell, revealing its ultrastructure.
In preparing the TEM, some cilia were cut
along their lengths, creating longitudinal
sections, while other cilia were cut straight
across, creating cross sections.
(b)
Cilia
1 µm
Longitudinal
section of
cilium
Cross section
of cilium

8. Differential centrifugation
Cell Fractionation
APPLICATION
Cell fractionation is used to isolate (fractionate) cell components, based on size and density.
First, cells are homogenized in a blender to
break them up. The resulting mixture (cell homogenate) is then centrifuged at various speeds and durations to fractionate the cell
components, forming a series of pellets.
Homogenization
Tissue
cells
1000 g
(1000 times the
force of gravity)
10 min
Homogenate
TECHNIQUE
Differential centrifugation
Supernatant poured
into next tube
RESULTS
In the original experiments, the researchers
used microscopy to identify the organelles in each pellet, establishing a baseline for further experiments. In the next series of experiments, researchers used biochemical methods to determine the metabolic functions associated with each type of organelle.
Researchers currently use cell fractionation to isolate particular organelles in order to study further details of their function.
20,000 g
20 min
80,000 g
60 min
Pellet rich in
nuclei and
cellular debris
150,000 g
3 hr
Pellet rich in
mitochondria
(and chloro-
plasts if cells
are from a
plant)
Pellet rich in
“microsomes”
(pieces of
plasma mem-
branes and
cells’ internal
membranes)
Pellet rich in
ribosomes

9. The size range of cells 10 m Human height 1 m Length of some nerve and
muscle cells
0.1 m
Unaided eye
Chicken egg
1 cm
Frog egg
1 mm
100 µm
Most plant and
animal cells
Light microscope
10 µm
nucleus
Nucleus
Most bacteria
Most bacteria
Mitochondrion
1 µm
Electron microscope
Smallest bacteria
100 nm
Viruses
Ribosomes
10 nm
Proteins
Lipids
Measurements
1 centimeter (cm) = 102 meter (m) = 0.4 inch
1 millimeter (mm) = 10–3 m
1 micrometer (µm) = 10–3 mm = 106 m
1 nanometer (nm) = 10–3 µm = 10 9 m
1 nm
Small molecules
0.1 nm
Atoms

10. Comparing the size of a virus, a bacterium, and an animal cell
Animal cell nucleus
While we’re on
the topic of
size...

11. Why Cells Are So Small: The SA:V Ratio
Surface area increases while
total volume remains constant 5 1
Total surface area
(height  width 
number of sides 
number of boxes)
Total volume
(height  width  length
 number of boxes)
Surface-to-volume
ratio
(surface area  volume) 6
150
125 12
750

12. Prokaryote bacteria cells Eukaryote animal cells
Types of cells
Prokaryote bacteria cells
- no organelles
- organelles
Eukaryote animal cells
Eukaryote plant cells

13. Why organelles? Specialized structures specialized functions
Containers
Compartments = different local environments
pH, concentration differences
distinct & incompatible functions
lysosome & its digestive enzymes
Membranes as sites for chemical reactions
Unique lipids & proteins
embedded enzymes & reaction centers
chloroplasts & mitochondria
Why organelles?
There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions.
Organelles as specialized structures
An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move.
Organelles as Containers
Nothing ever invented by man is as complex as a living cell. At any one time hundreds of incompatible chemical reactions may be occurring in a cell. If the cell contained a uniform mixture of all the chemicals it would not be able to survive. Organelles surrounded by membranes act as individual compartments for these chemical reactions. An example of the second type of organelle is the lysosome. This structure contains digestive enzymes, these enzymes if allowed to float free in the cell would kill it.
Organelle membranes as sites for chemical reactions
An example of the third type of organelle is the chloroplast. The molecules that conduct the light reactions of photosynthesis are found embedded in the membranes of the chloroplast.

14. Cells gotta work to live!
make proteins
proteins control every cell function
make energy
for daily life
for growth
make more cells
growth
repair
renewal

15. Proteins do all the work!
cells
DNA
Repeat after me…
Proteins do all the work!
organism

16. Cell functions Building proteins copy DNA DNA -> RNA build proteins
process proteins
Folding, modifying
Remove amino acids
Add molecules (e.g. glycoproteins)
address & transport proteins

17. Protein Synthesis Organelles involved nucleus ribosomes
endoplasmic reticulum (ER)
Golgi apparatus
vesicles
The Protein Assembly Line
Golgi apparatus
nucleus
ribosome ER
vesicles
The Endomembrane System

18. What kind of molecules need to pass through?
Nucleus
histone protein
chromosome
DNA
Function
protects DNA
Structure
nuclear envelope
double membrane
membrane fused in spots to create pores
nuclear
pores
pore
nuclear envelope
nucleolus
What kind of molecules need to pass through?

19. production of mRNA from DNA in nucleus
nuclear
membrane 1
production of mRNA from DNA in nucleus
small
ribosomal
subunit
large
cytoplasm
mRNA
nuclear pore 2
mRNA travels from nucleus to ribosome in cytoplasm through nuclear pore

21. Nucleolus Function ribosome production
build ribosome subunits from rRNA & proteins
Ribosome assembly is completed in cytoplasm
small
subunit
large subunit
ribosome
rRNA &
proteins
nucleolus

22. Ribosomes Function protein production Structure rRNA & protein
small
subunit
large
Function
protein production
Structure
rRNA & protein
2 subunits combine
0.08mm
Ribosomes
Rough ER
Smooth
The genes for rRNA have the greatest commonality among all living things. There is very little difference in the DNA sequence of the rRNA genes in a humans vs. a bacteria.
Means that this function (building of a ribosome) is so integral to life that every cell does it almost exactly the same way.
Change a base and this changes the structure of the RNA which causes it to not function.

23. Types of Ribosomes Free ribosomes suspended in cytosol
synthesize proteins that stay in cytosol
Bound ribosomes
attached to endoplasmic reticulum
synthesize proteins for export or membranes
membrane proteins

24. Endoplasmic Reticulum
Function
processes proteins
manufactures membrane
synthesis & hydrolysis of many compounds
Structure
membrane connected to nuclear envelope & extends throughout cell
accounts for 50% membranes in eukaryotic cell

25. Types of ER
rough
smooth

26. Smooth ER function Membrane production Metabolic processes
Lipid Synthesis
Glycogen hydrolysis (in liver)
Drug detoxification (in liver)

27. Membrane Factory Build new membrane synthesize phospholipids
ER membrane expands
buds off & transfers to other parts of cell.

28. Which cells have lot of rough ER?
Rough ER function
Produces proteins for export out of cell
protein secreting cells
packaged into transport vesicles for export
Which cells have lot of rough ER?
Which cells have a lot of ER?
protein production cells like pancreas = production of digestive enzymes (rough endoplasmic reticulum from a cell of exocrine pancreas (88000X))

29. Synthesizing proteins
cytoplasm
cisternal
space
mRNA
ribosome
membrane of
endoplasmic reticulum
polypeptide
signal
sequence
ribosome

30. Which cells have lots of Golgi?
Golgi Apparatus
Function
finishes, sorts, tags & ships products
like “UPS shipping department”
ships products in vesicles
membrane sacs
“UPS trucks”
transport vesicles
secretory
vesicles
Which cells have lots of Golgi?
Cells specialized for secretion?
endocrine glands: produce hormones
pituitary, pancreas, adrenal, testes, ovaries
exocrine glands: produce digestive enzymes & other products
pancreas, mammary glands, sweat glands

31. Golgi Apparatus

32. Vesicle transport vesicle budding from rough ER fusion of vesicle
with Golgi
apparatus
migrating
transport
protein
ribosome

33. The Endomembrane System
Putting it together…
The Endomembrane System
proteins
transport
vesicle
Golgi
apparatus
smooth ER
rough ER
nuclear pore
nucleus
ribosome
cell
membrane
protein secreted
cytoplasm

36. Any Questions!!

37. Can I offer you something in
A Computer Animation?

38. Or perhaps something more
in a silly rap song?!?

39. Review Questions

40. 1.. In which cell would you expect to find the most smooth endoplasmic reticulum?
Muscle cell in the thigh muscle of a long-distance runner
Pancreatic cell that manufactures digestive enzymes
Macrophage (white blood cell) that engulfs bacteria
Epithelial cells lining the digestive tract
Ovarian cell that produces estrogen (a steroid hormone)
Answer: e
Source: Taylor - Student Study Guide for Biology, Sixth Edition, Test Your Knowledge Question #18

41. 2. In which cell would you expect to find the most bound ribosomes?
Muscle cell in the thigh muscle of a long-distance runner
Pancreatic cell that manufactures digestive enzymes
Macrophage (white blood cell) that engulfs bacteria
Epithelial cells lining the digestive tract
Ovarian cell that produces estrogen (a steroid hormone)
Answer: b
Source: Taylor - Student Study Guide for Biology, Sixth Edition, Test Your Knowledge Question #19

42. 3. Of the following, which is probably the most common route for membrane flow in the endomembrane system?
Golgi → lysosome → ER → plasma membrane
tonoplast → plasma membrane → nuclear envelope → smooth ER
nuclear envelope → lysosome → Golgi → plasma membrane
rough ER → vesicles → Golgi → plasma membrane
ER → chloroplasts → mitochondrion → cell membrane
Answer: d
Source: Barstow - Test Bank for Biology, Sixth Edition, Question #20