Cells and Cell Organelles
Introduction
In laboratory 1 you examined eukaryotic cells with the light microscope.
The invention of the electron microscope with its subsequent application
to biological materials in the 1930's gave new impetus to the study of
cellular structure. An electron microscope utilizes an electron beam instead
of a light beam, while the lenses are electromagnets instead of glass.
The main advantage of the electron microscope is in its greater resolution,
with objects in the order of 50 or 60 nanometers being visualized compared
with one micrometer maximum resolution with the light microscope. The
electron microscope has allowed us to visualize subcellular structure
and in conjunction with biochemical studies we are now able to ascribe
functions to these structures.
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Compare images of the following cells, taken with a light microscope and an
electron microscope.
- Prokaryotic Cells
- Eukaryotic Animal Cells
- Eukaryotic Plant Cells
When examining each image consider the following questions:
- How do you know if it is a prokaryotic cell?
- What group of organisms consist of prokaryotic cells?
- How do you know if it is a eukaryotic cell? What types of organisms
possess eukaryotic cells?
- What structures can be seen only with the electron microscope?
Examine the Electron micrographs of the cells
below:
By using your notes, the text, be able to recognize the
nucleus, nucleolus,
chromatin,
cell wall,
plasmalemma
or cell membrane, flagella,
cilia,
microvilli,
Golgi apparatus,
mitochondria with
cristae,
chloroplasts with
grana, and stroma,
rough
endoplasmic reticulum with ribosomes,
smooth endoplasmic reticulum and lysosomes.
When examining each image consider the following questions:
- How many of these structures are membranous in their basic construction?
- Does the relative abundance of organelles like the rough endoplasmic reticulum
or mitochondria tell you anything about the functions of a cell?
- Which of the structures are unique to plant cells?
- Which structures are common to both plant and animal cells?
- Which structures are common to all cellular life forms?
First published Sept 95: Modified June 2020
Copyright © Michael Shaw 2019 (Images and Text)
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