Campbell et al., Chapter 7, emphasis is on eukaryotic cells
Euglena complex Eukaryotic cell - self sufficient, swim, see, photosynthesize
TRANSPARANCY (Fig. 28.3)
Protozoan vs. Metazoan complex, starts as 1 cell.
divide (Mitoses) - daughter cells
control of gene expression (in multicellular organism):
(1) different genes turned on in different cells (and at different times)
(2) ALL CELLS HAVE SAME GENES - CELLS DIFFERENT BY WHICH GENES ARE TURNED
(3) but this can be fairly permanent, developmental change in gene regulation
TRANSPARENCY (Fig. 7.1) gives relative sizes and emphasizes the importance
of light and electron microscopy. (Also note that Appendix 4 on p. A-7 compares
light and electron microscopes.) Dyes (that absorb light) are used to highlight
substructures in cells. Consider, for instance, the word "chromosome"
which translates to "colored body." Similarly, electron dense
materials, heavy metals like osmium, uranium and lead create an electron
density in the EM. Since I have done some EM, I offer these pictures to
give you a feeling of how EM is done. Sections are cut with an ultramicrotome
using a diamond knife
and sections, floated onto water are picked up on small copper grids.
The grid is put into an evacuated column in the EM,
and, at low magnification, a ribbon
of sections can be seen.
The cell membrane is a selective barrier to polar, charged, hydrophilic
molecules and ions. These need to be pumped at the expense of energy or
come through specific channels (pore molecules) through the membrane (more
later in membrane coverage).
Eukaryotic cells have specific little bodies that are the small cell parallel
of organs in the body, and hence they are called "organelles."
TRANSPARENCY (Fig. 7.8) plant cell, note cell wall, plasmodesmata, chloroplasts
and large vacuole.
TRANSPARENCY (Fig. 7.7) animal cell. Below, we will go through the following
structures one at a time: nucleus, endoplasmic reticulum (rough and smooth),
Golgi apparatus, flagellum
Nucleus - double envelope with pores
TRANSPARENCY (Fig. 7.9)
TRANSPARENCY (Fig. 7.11) Ribosomes & RER (rough endoplasmic reticulum)
where mRNA is translated into protein, "rough" describing the
ribosomes that can be seen in the electron microscope. Also, here is an
EM from my work showing RER.
There is also smooth ER where reactions other than protein synthesis take
place, such as steroid hormone synthesis, detoxification of substances in
liver. Liver hepatocytes detoxify and barbiturates induce an increase in
the "microsomal fraction," smooth ER as seen after grinding and
spinning down in a centriguge tube (see TRANSPARENCY [Fig. 7.3])
TRANSPARENCY (Fig. 7.10) Also free ribosomes and polysomes in the cytoplasm
that make proteins that go to different places.
Protein synthesis - goes at 10 amino acids per second
TRANSPARENCY (Fig. 7.12) Golgi apparatus receives vesicles from ER (at cis
face) and send secretory products that bleb off (from trans side). reactions
after protein synthesis (post-translational modification of proteins) take
place in Golgi complex.
It is very interesting to consider the different routings for different
proteins in the cell.
TRANSPARENCY (Fig. 8.8) this figure ("sidedness of the plasma membrane")
reminds us that inside the ER, Golgi complex, or vesicle is outside the
cell, much like inside the gut is outside the body.
TRANSPARENCY (Fig. 7.17) Mitochondria has a inner and outer membranes, the
inner one with shelves called cristae.
The function of the mitochondrion in ATP production is covered more in Chapter
Second semester, we introduce the speculation that mitochondria (and chloroplasts),
with their double membranes, are evolved from prokaryotes, engulfed into
TRANSPARENCY (Fig. 7.18) chloroplast with 2 membranes plus granum with thylakoid
membranes, frets and stroma. Note that the pigmernts for photosynthesis,
in order to be absorbed by light, are deployed in multiple layers of membranes.
Lysosomes, need to introduce phagocytosis (phag - eat as in hyperphagic,
eating too much, or bacteriophage, a virus that infects bacteria) TRANSPARENCY
Lysosomes merge and digest.
This also applies to autophagy, where cell eats itself in a process of turnover
of its components.
Here is a picture from my
own work of lysosomes merging with recycled membranes in the Drosophila
visual receptor, like TRANSPARENCY Fig. 7.13 in your text.
As you will see in the membrane lecture and in the genetics coverage, there
are "lysosomal storage diseases," Tay Sachs being an example where
there is a log jam of turnover with a corresponding buildup.
centrioles and cell division TRANSPARENCY (Fig. 7.22)
flagella and cilia - "9 + 2" arrangement TRANSPARENCY (Fig 7.24)
Paramecia swimming cilia - beat reverses when bump or sperm flagella TRANSPARANCY
dynein motor molecule for transport TRANSPARANCY (Fig. 7.21)
TRANSPARENCY (Fig. 7.27)Microfilaments
Actin - G (globular) -> F (filamentous)
Myosin - 2 heavy chains and 4 light chains)
also many other functions, streaming and anchoring of cytoplasm
TRANSPARANCY (Fig. 7.30)
Tight , Gap, Desmosome
This page was last updated 6/18/02
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