Scientific Inquiry, Cell Theory and Microscopy.

Define hypothesis

A testable explanation of an observation.

What is Deductive Reasoning?

"If...hypothesis is correct then....prediction." General to specific.

Explain what is means by a Controlled Experiment

Just one (or a few) factors are changed at a time, while all others are kept constant. This rules out other factors.

If prediction is correct then the hypothesis is ....?

supported (not proven).

If the prediction doesn't work then the hypothesis is...?

contradicted.

Compare and contrast Hypothesis vs Theory

A hypothesis is a testable explanation of an observation, whereas a theory is a broad explanation supported by many observations or experiments.

Cell Theory Principle 1

All Living Organisms are composed of cells.

Cell Theory Principle 2

The Cell is the basic unit of life.

Cell Theory Principle 3

Cells arise by division of pre-existing cells.

Eukaryotic Cells Size

Approximately 10-100 μm.

Prokaryotic Cells Size

Approximately 1-10 μm.

Conversion to Millimeters

1000 μm = 1 mm; 1 μm = 0.001 mm.

Describe the basic principles of Brightfield Microscopy?

Used in Cell Biology labs; simple and inexpensive; stains can be used; limit of resolution: 0.2 μm/200 nm.

Describe the basic principles of Fluorescence Microscopy?

Absorption of specific light wavelengths (colours) by specimen or fluorescent dye; re-emission as another light wavelength (colour).

Describe the basic principles of Confocal Microscopy?

3D fluorescence microscopy; 'Optical Sections'.

Describe the basic principles of Electron Microscopy?

Limit of Resolution: 2 nm (0.002 μm); uses electron beam instead of visible light; lenses are electromagnets; can see cell ultrastructure.

Describe the basic principles of Transmission Electron Microscopy (TEM)

Very thin section of sample is used; thin section of specimen is seen.

Describe the basic principles of Scanning Electron Microscopy (SEM)

Scans surface of sample; 3D surface view is seen.

explain Light Microscopes(LM):

- light is passed through the specimen and then glass lenses.

The lenses refract (bend) the light in such a way that the image of the specimen is magnified as it is projected into the eye.

Fluorescence microscopy: What sort of light is used?

Ultraviolet Radiation

Fluorescence microscopy: How are the cellular components made visible?

Locations of specific molecules are revealed by labeling the molecules with fluorescent dyes or antibodies, which absorb ultraviolet radiation and emit visible light.

Confocal microscopy: What is the main advantage of confocal microscopy?

The primary advantage of confocal microscopy is its ability to produce high-resolution and high-contrast images by eliminating out-of-focus light. It uses a pinhole aperture to focus the light and only collect fluorescence from a single focal plane, creating optical sections of the specimen.

Electron microscopy : What is used to 'illuminate' the sample?

An Electron Beam

Electron microscopy : What is used to focus the image?

Electromagnetic lenses are used to focus the electron beam and thus the image. These lenses use magnetic fields to control the path of the electrons.

Electron microscopy : What is the main advantage of electron microscopy?

The main advantage of electron microscopy is its significantly higher resolution compared to light microscopy. This is because an electron beam has a much shorter wavelength than visible light, allowing it to resolve much smaller structures.

Electron microscopy : What are the names (and acronyms) of the two main types of electron microscopy?

Scanning Electron Microscopy (SEM)

Transmission Electron Microscopy (TEM)

Electron microscopy : When you look at electron micrographs, how do you tell which method has been used (if it isn't stated)?

SEM images typically show the surface of the specimen in great detail, providing a 3D-like appearance. The images have depth and texture, emphasizing the morphology and topography of the specimen.

TEM images, on the other hand, provide detailed internal structures of the specimen and appear more like 2D slices. The images are often flat and show high-resolution details of thin sections of the sample.

Electron microscopy : Can you use electron microscopy to investigate living cells and processes inside the cells as they happen?

No you can not. The processes involved would kill a living cell.