The interior is an aqueous cytosol.
The cytosol and various macromolecules and organelles immersed in it
comprise the cytoplasm.
Prokaryotes do not possess membrane-bound organelles.
DNA is located in a nucleoid region, and the cell is encased in a
rigid cell wall.
Eukaryotic cells typically range from 10 - 100 Ám in diameter.
Prokaryotic cells are even smaller, usually less than 10Ám.
Unless cell is naturally pigmented, image has little contrast.
When recombined the two beams interfere and enhance the variation of
optical density of the sample.
These fluorescent substances absorb ultraviolet light and emit visible
light to reveal the desired structures.
A computer cam regenerate a 3-D view by combining images of several
sections of the specimen.
The top photo shows in-focus nerve cells and support cells of nerve
The bottom photo is a standard fluorescence micrograph.
Thus small size facilitate the exchange of material into and out of
The organelles are embedded in a semifluid cytoplasm and enclosed in a
Organelles found in animal cells but not in plant cells include
lysosome and centrosome.
Chloroplasts perform photosynthesis.
A central vacuole stores material.
A rigid cell wall made of cellulose enclose the plasma membrane.
Plasmodesmata provide cytoplasmic connections through openings in the
The nucleus is surrounded by a double membrane called nuclear
envelope, which is perforated with nuclear pores.
Within the nucleus can be found:
Rough ER is studded on its outer surface with ribosomes to produce
Smooth ER lacks ribosomes and is involved in lipid synthesis.
Transport vesicles bud off and carry ER products to the Golgi
apparatus and other destinations.
Lysosomes digest (hydrolyze) materials taken into the cell and recycle
Molecules can be engulfed by infolding of the plasma membrane,
yielding a food vacuole.
The food vacuole then fuses with a lysosome for digestion -
Top: a lysosome engulfs 2 disabled organelles, a mitochondrion and a
Bottom: a lysosome fuses with a vesicle containing a damaged
It is usually the largest organelle seen under the microscope.
The complex then moves along "monorails" of microtubules.
The cytoplasm can switch between a fluid state called sol, and a
stiffer state called gel.
Breakdown of the actin network squeezes the cytoplasm into the sol,
forming a pseudopodium.
A layer of cytoplasm cycles around a plant cell, moving over a carpet
of parallel actin filaments.