Connect
• What are you made of?
• What is every living thing on Earth
made of?
• How did scientists find this out?
D. The Cell Theory
2 parts
1.
Cells are the basic unit of structure and function of
all living things. (All living things are made of one or
more cells, which carry out the life functions.)
2.
All cells come from pre-existing cells.
Development of the Cell Theory
•
Before scientists were able to develop the cell theory,
the microscope needed to be invented so they could
see cells.
3 Exceptions to the Cell Theory
• After scientists developed the cell theory, they came up
with some exceptions to it.
1. The first cell could NOT have arisen from a previously
existing cell (it must have developed from noncellular
matter).
THE FIRST CELL?: Scientists at Harvard
Medical School have designed what they
think is a reasonable model for the first
cell on Earth, some 3.5 to four billion
years ago.
2. A virus is NOT a cell; but it does have
genetic material (DNA). Also, it can only
live inside a host cell. Outside the host
cell there is no sign of life.
3. Mitochondria and chloroplasts, which are
cell organelles (parts) contain genetic
material (DNA) and can replicate
themselves in living cells.
Chunk!
• Give the two parts of the cell theory.
• How did scientists discover cells?
• Describe each of the three exceptions
to the cell theory.
Connect!
• Look at your hand and a leaf through a hand
lens. Can you see cells? Why not?
• Why are hand lenses and microscopes
used?
• How can we measure a cell?
• Why don’t most people wear a white stained
shirt out to a restaurant?
• What do you think the purpose of using a
stain is in scope work?
Methods of Cell Study
Instruments
1. The Compound Light Microscope
•
•
is still the major tool of cell study
Uses 2 lenses or sets of lenses to form an
enlarged image
2. The Electron Microscope
• most powerful
• magnification of more than
250,000X
• can only be used on dead
organisms
• In 1997, researchers using the
Scanning Interferometric Apertureless
Microscope (SIAM) viewed features
about 4 atoms (1 nm) in diameter!
3. The Dissecting Microscope
• gives a 3-D image for dissection
• very low power of 10X or 20X
4. The Ultracentrifuge
• separates cell parts on the basis of
density
5.Microdissection instruments
• tiny instruments used for the dissection of
individual cells and/or transfer of cell
organelles
• ex: nuclear transfer during cloning,
intra-cytoplasmic sperm injection for
infertility, or cancer cell studies
Laser/film Microdissection
of follicular thyroid
carcinoma (FTC).
A, before microdissection;
B, after microdissection;
C, microdissected cells
attached to the cap.
Using the Microscope
On the stage
Through the lens
Centering the image
Measurement
1. Micrometers
• because cells are so small, a small unit
of measurement is needed
• micrometers are used; 1 mm = 1000 um
microscopic field
metric ruler
Staining
1. Even with microscopes, cell structures
(organelles) may not be clearly visible.
Staining will help these structures
(nucleus, cell wall, cell membrane,
cytoplasm) show up better under the
microscope.
2. Examples of stain include methylene
blue and iodine.
Unstained
Cheek Cells
Stained
Cheek Cells
Chunk!
• What instrument had to be invented in order for scientists to
develop the cell theory?
• Name the type of microscope we use.
• What is the strongest type of microscope? What is its
disadvantage?
• What does an ultracentrifuge do?
• What cell parts are most dense? least dense?
• What is microdissection, and what are 2 uses?
• What unit of measurement is used microscopically?
• 1 mm = ??? um
• What technique makes cell organelles more visible?
• Name 2 stains.
• What 3 organelles are generally visible with a compound
scope?
Name the
parts and
their
functions.
Just for Fun…
Image Sources
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Background image - http://www.brighamandwomens.org/publicaffairs/Images/Cells.jpg
The first Cell –www.scientificamerican.com/media/inline JANET IWASA
Plant cell –http://www.williamsclass.com/SeventhScienceWork/ImagesCells/CellWall.jpg
Microscope to label - http://www.franklin.k12.ma.us/~allenc/014E2A6A-0066418D.1/microscope.gif
Virus - http://www.ucmp.berkeley.edu/alllife/virus.gif
Mitochondria - http://biology.georgefox.edu/~jduerr/400px-Mitochondria.gif
Chloroplast - http://biology.unm.edu/ccouncil/Biology_124/Images/chloroplast.bmp
Microscope - http://crescentok.com/staff/jaskew/ISR/equip/micro.gif
Letter e, stained and unstained cells, electron microscope http://www.google.com/imgres?imgurl=http://crescentok.com/staff/jaskew/ISR/equip/micro.gif&imgrefurl=http://crescentok.com/staff/jaskew/ISR/equip/equip4.htm&h=441&
w=472&sz=44&tbnid=IBLNc48P3MC_rM:&tbnh=121&tbnw=129&prev=/images%3Fq%3Dcompound%2Blight%2Bmicroscope%2Blabeled&usg=__oIn7mnt96QwnzsIqoHQaB7fmSw=&ei=G6tdS7bZOszd8Qbcz9X1BA&sa=X&oi=image_result&resnum=1&ct=image&ved=0CA4Q9QEwAA
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Mammoth cartoon - http://bizzarroworld.homestead.com/files/early_microscope_cartoon.jpg
Dissecting microscope - http://www.celestron.com/c3/images/files/product/44200_laboratorydisse_mid.gif
Centrifuge - http://www.marketlabinc.com/files/products/images/medium/ml5400Centrifuge.jpg
Cell fractionation - http://www.freewebs.com/ltaing/bioart.gif and
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A1129&rendertype=figure&id=A1135
Microdissected thyroid cells - www.nature.com/.../v82/n12/full/3780578a.html
Nuclear transfer and sperm injection - http://www.pbs.org/wgbh/nova/baby/glossary.html