Cell Theory and CellsBiology

Microscopes• How we see cells and what is inside of cells• Van Leeuwenhoek: 1st compound light microscope (x270)

• Hooke looked at cork cells (dead plant cell) underneath a compound microscope and described them as cells

Light Microscopes• Uses visible light and lens• Can see living samples • Can see color image• Relatively inexpensive• Two Types:

• Compound Microscopes• contain several lenses

• Maximum Magnification: x1500• Maximum Resolution: 200 nanometers

• Due to the wavelength of light• Dissecting Microscopes (stereoscopic microscope)

• Low final magnification• 2 eyepieces to produces a 3D stereoscopic view• Useful for dissections (when you need space between the lenses

and the stage

Compound Light Microscope

Dissecting Microscope

Transmission Electron Microscope• a microscope that uses a beam of accelerated electrons that

pass through the tissue sample

• Wavelength of an electron is smaller than light’s

• Produces a 2D image• Resolution: 50 picometers (5.0 x 10-13 meters)• Magnification: x10,000,000• Allows you to see inside the cell

• including cell organelles

Scanning electron Microscope

• Produces images of a sample by scanning it with a focused beam of electrons the “bounce” off the surface and then are detected.

• Give information about the sample's surface topography and composition.

• Shows 3D structure of the sample

• Resolution: 10 nanometers (1.0 x10-10)

• Magnification: x100,000

Electron MicroscopyThe preparation of a sample for electron microscopy is a complex process.

● Chemical Fixation: Stabilizing an organism/sample's mobile macrostructure

● Cryofixation: Freezing the sample very rapidly to preserve its state

● Dehydration: Removing the water from a specimen, for example, by replacing it with ethanol

● Embedding: Embedding in resin, ready to be sectioned● Sectioning: Cutting the sample into thin strips that are semi-

transparent to electrons, for example with a diamond knife● Staining: Using heavy metals to scatter electrons and produce

contrast● Freeze Fracturing: Freezing the sample rapidly, and then

fracturing it, for example, when viewing cell membranes● Mounting: Placing the sample on a copper grid

Plicker Question1. How are scanning electrons different from transmission

electrons?a. Produces a 2D image b. Produces a 3D imagec. Electrons pass through the specimend. Higher magnification

2. Which of the following microscopes would be best for viewing the mitochondria of the cell?a. Compound Lightb. Dissecting c. TEMd. SEM

3. Which of the following microscopes would be best for viewing the process of cell replication?a. Compound Lightb. Dissectingc. TEMd. SEM

History of the Cell Theory

Cell Theory

1. All living organisms are made of cells (they may be unicellular or multicellular)

2. Cells arise from preexisting cells (Not derived from spontaneous generation)

3. The cell is the basic unit of lifea. Has a plasma membrane/cell membraneb. Has genetic material (DNA)c. Has ribosomesd. has a cytoplasm/cytosol

Plicker Question: What macromolecules primarily makes up the cell membrane?A. Polypeptides B. Lipids C. Carbohydrates D. Nucleic Acids

Cells• Smallest unit of life• Cells→Tissues→Organ→Organ System→Organism

• Prokaryotic• Unicellular organism• Lacks a nucleus • Lacks membrane

bound organelles• Eukaryotic

• Has a nucleus• Has membrane bound

organelles• can be unicellular or

multicellular

Prokaryotic Cell Pili is like cilia except it has a special function for conjugation (reproduction) for bacteria cellsProkaryotic Flagellum has a different structure than eukaryotic flagellumCapsule or Slime layer is NOT always present

Animal Cell

Plant Cells

Homework Due: 10/5-6Cells, the basic units of life, are often compared to a business, a factory, an entire city or a planet. In this assignment you need to make analogies to compare the function of the plant or animal cell to the part and functions of an entire city. To accomplish this, you must complete the following tasks:

Task 1: Create analogies between a plant or animal cell’s parts and a city’s (or any analogy) parts by completing the Cell Analogy template

When making the analogies between your cell and your city (or other analogy), the functions of the city part and cell part must match, not the appearance!

You will be allowed to use this sheet on your vocabulary test.

Bell Ringer: *Turn into Bin

In paragraph form, compare and contrast prokaryotic and eukaryotic cells

In a second paragraph compare and contrast plant and animal cells.

*Paragraphs should be 5-7 sentences at least. They also should include AT LEAST 3 comparisons and AT LEAST 3 contrasts for each question.

The Plasma Membrane