BIOL130 Lecture Notes - Lecture 1: Dark Field Microscopy, Antonie Van Leeuwenhoek, Golgi Apparatus

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1 Aug 2016
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Taught by: H.E.
BIOL 130 – Week One Notes
Historical light microscopy
-Robert Hooke (1635-1703)
oFirst microscope (built a compact version)
oViewed slices of cork – looked at the remains of cell walls when the
living part was gone
o“cellula” (little rooms that monks lived in)  “cells”
-Antoni Van Leeuwenhoek (1632-1723)
oKnown as the “father of microbiology” after discovering bacteria in his
mouth
oMerchant who made glass lenses for a living  huge iprovement in
quality of lenses – nearly 300x magnification
oFirst to observe “animalcules” (single-celled organisms), protists from
pond water, bacteria from his mouth, blood cells, banded pattern in
muscle cells, sperm from…
-Progress stalled for a century or so – limited resolving power, emphasis on
description rather than explanation
-1830s – compound microscope
oImproved magnification and resolution
oAllowed visualization of objects less than 1 μm
The discovery of the cell
-1833Robert Brown (botanist)
oNoticed that every plant cell contained a round structure (“kernel” 
“nucleus”)
-1838Matthias Schleiden (botanist)
oDiscovered that all plant tissues are composed of cells
oEmbryonic plant always arose from a single cell
-1839Theodor Schwann (zoologist)
oSimilar observations in animal cells  recognition of structural
similarities between plants and animals
oFormulated the Cell Theory
Cell theory
-All organisms consist of one or more cells
-The cell is the basic unit of structure, life and reproduction for all organisms
-Added 20 years late: all cells arise only from pre-existing cells
Facts
-For us – something we know or believe to be true
-For Scientists – an attempt to state our best or current understanding based
on observations and experiments; valid only until revised or replaced by a
better understanding attained after further experimentation and observation
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Taught by: H.E.
The Scientific Method
-Based on making observations whether in their natural environment or
situations that we create
-Hypothesis is always being tested; once it has and succeeds under many
different conditions, it becomes acknowledged as a theory
-Steps:
oMake observations
oUse inductive reasoning to develop tentative explanation (Hypothesis)
oMake predictions based on your hypothesis
oMake further observations or design and carry out Controlled
Experiments to test your hypothesis
oInterpret your results to see if they support your hypothesis
Theory
-A hypothesis that has been tested critically under many different conditions,
by many different investigators, and by using a variety of different
approaches
-By the time an explanation is regarded as a theory, it is widely accepted by
most scientists
-The “solid ground” of science – evolution, germ theory, cell theory
oPeople can doubt all sorts of things, but scientifically, these theories
are the solid ground
Law
-When a theory has been thoroughly tested and confirmed over many years
by large numbers of investigators – so much so that there is no doubt of its
validity (= a more untouchable version of a theory)
oEx. gravity, laws of thermodynamics, laws that govern the behaviour
of gases
-Biologists are very conservative about using this term because as soon as we
say something and think that a conclusion can be drawn, something new is
discovered
“Strands” of Cell Biology
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Taught by: H.E.
-Cytology- just looking at cells processed in away that they aren’t alive
anymore (old-school biology)
Microscopy
-Light Microscopy:
oBright field = ordinary white light (unstained, nothing)
oPhase Contrast = playing around with light
oDye still proves to give a much more in-depth look of what’s going on
inside the sperm
-Fluorescence Microscopy:
oDark field microscopy
oWe’re not just throwing white light; we’re throwing light at different
wavelengths! ( different colours) and tagging molecules
-Electron microscopy
oBombarding with electrons, not photons
o2 different approaches: Scanning (SEM) and Transmission (TEM)
oThink of it as: S for Surface because you se the surface, 3D, e.t.c. and T
for Through because you’ve sliced it open and can see through it
Ex. If you’re interested in mitochondria, use TEM because you
need to see through the cell in order to get to organelles
(Nucleus and Rough ER are shown in image on lower-right)
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