Cell - ANSThe basic unit of biology. Everything is made of multiple or a single cell. By studying
the cell, we can appreciate the capabilities and limits of life. Cells have the ability to grow,
change, reproduce, become specialize, respond to stimuli, and conduct homeostasis.
Three Stands of Modern Cell Biology - ANSCytology, genetics, and biochemistry
Robert Hooke - ANSDiscovered cells in 1665 while studying cork. Although these cells were
actually dead plant tissue. His microscope enlarged items 30x their size. He was limited by the
magnification power of his microscope.
Antonie Van Leeuwenhoek - ANSFirst to observe living cells with his new microscope.
Two factors restricted progress in early cell biology - ANS1. Microscopes had limited resolution,
or resolving power (ability to see fine detail)
2. The descriptive nature of cell biology: the focus was on observation, with little emphasis on
explanation
Resolving Power (resolution) - ANSAbility to see fine detail
Compound Microscope - ANSBy the 1830s, compound microscopes were used
1. These had two lenses
2. Both magnification and resolution were improved
3. Structures only 1 micrometer (um) in size could be seen clearly
Robert Brown - ANSDiscovered nucleus in plant cell
Matthias Schleiden - ANSConcluded that all plant tissues are composed of cells
Thomas Schwann - ANSMade the same conclusion for animals as Schleiden for plants. Saw
that animal cartilage had thick walls like plant cells and created single unified theory of cellular
organization (Cell Theory):
1. All organisms consist of one or more cells
2. The cell is the basic unit of structure for all organisms
3. All cells arise only from preexisting cells (Virchow added)
Nagelli - ANSCell Division
, Cytology (Hollow Vessel) - ANSFirst Strand to emerge three centuries ago with light
microscope. Cytology is the study of cells and focuses mainly on cellular structure and
emphasizes optical techniques. Ex. Cell Theory, Descriptions
Microscopy (Cytology) - ANSInvaluable in helping cell biologists deal with the problem of small
size of cells and their components
Micrometer (Um) - ANSAlso called the micron, is one millionth of a meter (10-6 m).
Ex. Bacteria Cells and organelles are few ums, Animal/Plant Cells are 10-20um
Nanometer - ANSUsed for molecules and subcellular structures too small to be seen in the light
microscope. The nanometer is one-billionth of a meter (10-9 m). Used to measure
macromolecules.
Angstrom (Å) - ANSAn angstrom is 0.1 nm, equals about the size of a hydrogen atom. It is used
in cell biology to measure dimensions within proteins and DNA molecules
Light Microscope - ANSThe light microscope was the earliest tool of cytologists
1. It allowed identification of nuclei, mitochondria, and chloroplasts within cells
2. Light microscopy is also called brightfield microscopy because white light is passed directly
through a specimen
Microtome - ANSAllowed preparation of very thin slices of samples
Dyes - ANSA variety of dyes for staining cells began to be used around the same time
Physical limits of resolution - ANSImproved optics and microscopic lenses, these developments
extended light microscopy to the physical limits of resolution imposed by the size of wavelength
lights.
Limit of Resolution - ANSHow far apart objects must be to appear as distinct. The smaller the
resolution the greater the resolving power, ability to see fine detail. Better microscopes have
lower resolution. The limit of resolution is half the wavelength of light.
Bright Field Microscopy - ANSSends white light through a specimen, but specimen must be
preserved or dead or stained. This may leave out what could be observed in living cells.
Phase of light - ANSPosition of the maxima and minima of light waves
Phase/Differential Inference Contrast - ANS1. Make it possible to see living cells clearly
2. The phase of transmitted light changes as it passes through a structure with a different
density from the surrounding medium
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