BIOL1004 Study Guide - Final Guide: Collagen, Mitosis, Centrosome
Cells and Microscopy
Cell theory
• All living organism are made up of cells and the materials produced by
them
• All cells come form pre-existing cells
• The cell is the smallest organisational unit
+note: viruses are not living
Eukaryotic cells
Prokaryotic cells
Algae, fungi, plants and
animals
Diverse single celled:
protists
DNA lies within the
bacterial cell in the
nucleoid
Size
Few µm- 1mm in
diameter and several cm
in length
> 1µm
Evolution
• ~ 800 years ago some cells remained attached after replication →
multicellular organism
• Multicellular organisms become different form each other →
differentiated
• Differentiate cells → tissues and organs
Multicellularity
• Requires: signalling, communication between cells, control of cell
death, adhesion and division
Advantages:
• Development of large body size → can occupy different environmental
niches
• Distribution of labour → different cells develop different capabilities
• Resilience → some cells can die without the organism dying as a
whole
• Surface area increases
History of cells
Year
Scientist
Observation
1665
Robert Hook
First to observe
and describe
cells by looking
at cork under a
microscope
1674
Anthonie Van Leeuwenhook
Observed and
described
components
inside cells,
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chloroplasts in
green alga
1828
Robert Brown (botanist)
First described
nucleus
Microscopy
Image quality is dependant on:
• Magnification- ratio of image to actual size
• Resolution- minimum distance between two distinguishable points
(depends on wavelength of light)
• Contrast- visible differences in parts of the sample → can be increased
by staining
Physical sectioning
• Embedded in plastic resin → thin slices
• With a microtome or cryosection (freezing the cutting)
Optical sectioning
• Light microscope can create images from deep within a sample
Microscope
Description
Avdantages
Light
microscope
• Use glass lenses to
illuminate and collect
light from an object
• Green light
• 1000x magnification
• resolution around
0.2µm
Confocal
microscopy
• Sample is illuminated
with a focused beam of a
high intensity laser
• Light emitted at the
sample passes through
a pin hole before
reaching a detector
• Out-of focus light does
not pass through the
pinhole and degrade the
image
• Increased resolution
• Ability to collect optical sections (creating
images from deep within a sample
• 3D view
• Living cells can be studied and dynamic
changes in subcellular organisation
observed
Electron
microscope
• Use magnets to
focus a beam of
electrons onto a
• 4000x better resolution than light
microscopes
• Allows structures smaller than 0.5µm to be
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sample
• Must be under
vacuum
seen
Transmission
electron
microscope
• Electrons pass
through sample onto
a screen or camera
• ‘Ultrathin’ sections
are stained with
heavy metals that
bind differentially to
different molecules
and stop electrons
passing through the
section
•
Scanning
electron
microscopes
• Beam of electrons is
scanned across
sample and electrons
that bounce off the
surface are shown on
a video monitor
•
In situ localisation of specific molecules
Meaning of in situ: following the dynamic of molecules and subcellular
components, in living cells
1. Florescent dyes
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Document Summary
Cell theory: all living organism are made up of cells and the materials produced by them, all cells come form pre-existing cells, the cell is the smallest organisational unit. Few m- 1mm in diameter and several cm in length. Dna lies within the bacterial cell in the nucleoid. > 1 m: ~ 800 years ago some cells remained attached after replication multicellular organism, multicellular organisms become different form each other differentiated, differentiate cells tissues and organs. Multicellularity: requires: signalling, communication between cells, control of cell death, adhesion and division. Advantages: development of large body size can occupy different environmental niches, distribution of labour different cells develop different capabilities, resilience some cells can die without the organism dying as a whole, surface area increases. First to observe and describe cells by looking at cork under a microscope. Observed and described components inside cells, chloroplasts in green alga.
