Connect

• What are you made of?

• What is every living thing on Earth made of?

• How did scientists find this out?

D. The Cell Theory2 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

Measurement1. 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 Stained

Cheek Cells 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• 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=__oIn7mnt96Qwnzs-IqoHQaB7fmSw=&ei=G6tdS7bZOszd8Qbcz9X1BA&sa=X&oi=image_result&resnum=1&ct=image&ved=0CA4Q9QEwAA

• 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