visualizing and understanding the cell cell theory introduction to microscopy

Visualizing and Understanding the Cell

Cell Theory

Introduction to Microscopy

Cell Theory and Scientists

• Van Leuwenhoek; invented the microscope and looked at pond water.

• Hooke: Looked at cork cells; little boxes--name of the cell

How can we define a cell?

Cell Theory

• The cell is the simplist unit of structure and function in living things.

• All living things are made of cells.

• All cells come from pre-existing cells.

• Scientists:– Schleiden: all plants

are made of cells.

– Schwann: all animals are made of cells.

– Virchow: all cells reproduce

How do you think these scientists determined this?

Microscopes

• Allow us to visualize cells.

• Many types: Serve Different Purposes– Light– Phase– Transmission– Scanning

Light

• Very simple, may be inexpensive.

• Oil needed for 100X lens.

• Limitation: specimen must be stained to see!

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Phase

• Has different sets of lenses to see living specimens without stain.

• Maximum size (1000X)

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TEM: Transmission electron microscope

• Uses electrons instead of light (very expensive)!

• Specimen stained with metals (like gold!)

• Electron beam transmits through the specimen and produces a highly magnified computer image.

• Magnification 10,000-50,000 X

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SEM: Scanning Electron Microscope

• Electron beam bouncing off objects stained with metals shows the surface of objects.

• Used to get surface detail of both large and small specimens.

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Quiz yourself…what type of microscope?

Mitochondria within a muscle cell…

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Amoeba engulfing its food…

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Surface of Red and White Blood Cells…

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Surface of the Moon…

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A Human Cheek Cell stained with Methylene Blue…

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So if we are using a microscope to look at them…how big are

cells?• Cells and cell parts

can be measured in micrometers.

• 1 meter contains 106 micrometers.

• Let’s practice converting!

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Estimating size of cells

• The size bar represents 100 micrometers.

• Can you estimate the size of the nerve cell?

• Axons (long stringy pieces?)

• Cell body (central portion)

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Cellsalive.com

• You will first do the activity “how big” to estimate the size of cells, make conversions and draw conclusions.

• Then you will use the website to research 20 essential organelles. Provide information about their structure, function and what types of cells they are found in!

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http://www.cellsalive.com/howbig.htm

Let’s Compare Cells: Prokaryotic and Eukaryotic

In your notebook use a Venn Diagram to compare and contrast the prokaryotic organism to the eukaryotic organism.

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Compare and Contrast: Multicellular vs. Unicellular

In your notebooks compare and contrast the paramecium to the human tissues.

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Compare and Contrast: On You Own

• Compare and contrast the Plant and Animal Cell coloring you have in your packet.

Microscope Lab

• HW: – Complete Definitions of introduction.– Form Hypothesis--use your Venn D’s to help

you (you do not have to use If…then format but you must explain WHY you are making your hypothesis)

Magnification

• Ocular Lens: Always 10X• Objective Lens: Varies--4 X; 10X; 40X; some

even 100X oil!

• Total magnification=Ocular X ObjectiveWhat is the total magnification if a student uses the 10X

objective lens?You MUST put total magnification on all pictures

drawn from microscopes :)

Watch how to focus; you will write the directions in your

notebook later• Put the slide on the stage and clip it down.• Put the 4X objective pointing to what you want to see on

the slide.• Look through the ocular. Use the coarse focus to get the

specimen in view.• Use the fine focus to make the specimen clear.• Move up to the 10X objective• Use only the fine focus to make the object clear.• Do the same to move up to the 40X.• Every slide you must start at the beginning!

Lab Goals

• To be able to focus a microscope and calculate total magnification.

• To visually compare: prokaryotic, eukaryotic, plant, animal, and tissue slides!

• To understand the structure and function of these different cell types.

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