Overview of Cells & Energy (Revision)

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1.1 Cell Theory

Robert Hooke(1665): Published first book on cells. Discovered cells when looking at cork under a microscope. Discovered cell structure of plants.

Anton von Leewenhoek (1650-1700):Dutch. First observed protists. With a simple lens(x200), he observed unicellular organisms & nuclei. By using his ability to grind lenses, he greatly improved the microscope as a scientific tool. He discovered bacteria, protozoa and other small life-forms which he called 'tiny animals'.

Mattias Schleiden(1838): Deduced theory of 'photogenesis' which states that all living things are made of cels or their derivitives.

Theodore Schwann(1839): With Schleiden, Schwann deduced the cell theory- that all animals and plants are made of cells and that within an organism all the cells are identical. Discovered Schwann cells.

Rudolph Virchow (1855): Deduced that all cells are created by other cells. Demonstrated that cell theory applies to diseased tissue as well as living tissue.

Jansen: Invented compound microscope.

Light Microscopes: Light from a source beneath the stage is transmitted through the two lenses in a series, the objective and the ocular (eyepiece) lenses to provide magnifications. Cannot resolve details better than about 0.2 mm(micrometers)

Advantages of light microscopes:

Enables user to see larger structures within eukaryotes and distinguish individual prokyrotes.

They are user-friendly: small, portable, easily-prepared slides, relatively cheap to buy and maintain.

Both living and dead material may be viewed.

Material is rarely distorted by preperation.

Thicker materials may be viewed

Allows experimenter to view image directly.

Allows for specimen to be observed in natural state.

Slides are simple to prepare



Can observe movement.

Electron microscopes: Uses an electron beam instead of a light beam, and electromagnets instead of lenses. Electrons are recorded on a photographic plate, which forms an image on screen.

Advantages or electron microscopes:

Magnifies over 500,000x

Resolving power for biological specimin around 1nm

3-D view instead of one.

Interior view

See organelles than cannot be observed w/ light microscope.

'Resolution': Ability to percieve fine detail. Expressed as the minimmum distance between two points for them to be visually distinct. Depends on the lens quality and the wavelength of light used.

'Magnification: The ratio between the size represented on the microscope and the actual size.

Organelle: A small body inside a cell with a specilised structure that performs a specific function. It also has its own protective membrane.

Relitive Sizes:

1nm: Membrane Thickness

10nm: Viruses

100nm: Bacteria

1-10mm(read'micrometer'): Organelles

less than or equal to 100mm(micrometers): Cells

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1 nm: Molecules

10 nm: Cell Membrane

75 nm: Virus

100 nm: Macromolecules

1 mm(micrometer): Bacteria

3 mm: Organelles

10 mm: Cell

Surface area to volume ratio: *The rate of the metabolism of a cell is a function of its mass to volume ratio.* The more active a cell's metabolism, the more material must be exchanged if the cell is to continue to function. The smaller the cell, the more efficent it is. Larger cells require more energy, but their surface area to volume is closer to one, making them less efficent.

Cell Nucleus: A membrane enclosed organelle containing ...

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