Notes on Cell Structures

Essay by starcraftgoddessHigh School, 12th grade October 2004

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Cytology is the study of cell structure

Cell is the simplest collection of matter that can live

Hooke discovered "cells"

Schleidan "all plants are composed of living cells"

Schwann "all animals are made of living cells"

Virchow "existing cells give rise to new cells"

Cell Theory

"All organisms are composed of one or more living cells"

"Cell is the most basic unit of function"

"All cells come from existing cells"

Light microscope (Leeuwenhoek- first to view living cell and sperm) no finer than 0.2 micrometer

* Visible light pass through specimen-lenses-(light refracts)-projected into eye, film, video screen

Cell ultrastructure- a cell's anatomy as revealed by an electron microscope

EMs have shorter wavelengths than the wavelengths of visible light

ScanningEM- surface coated with a film of gold, topography of the specimen, depth of field, 3-D

TransmissionEM- internal, electron beam through specimen, electromagnets used to magnify and focus

Resolution- measure of the clarity of the image; the minimum distance two points can be separated

Magnification- apparent increase in object size; ratio of an object's image to its real size

Cell fractionation

* Enables a researcher to prepare specific components of cells in bulk quantity in order to study their composition and functions

* Process of taking cells apart, separating the major organelles so that their functions can be studied

* Centrifuge spins it at various speeds; ultracentrifuges spin at 130,000 rpm

* Homogenization is the disruption of cells; pellets (heavier) at the bottom; supernatants on top

* The supernatant is transferred to another tube and centrifuged again at a higher level

* Mitochondria are the sites of cellular respiration

All cells are bounded by the plasma membrane (selectively permeable with protein channels)

* Cytosol is a semi-fluid substance in which organelles are found

* Cytoplasm is the entire region between the nucleus...