Cell Biology

Campbell et al., Chapter 7, emphasis is on eukaryotic cells

Euglena complex Eukaryotic cell - self sufficient, swim, see, photosynthesize
Prokaryote, Eukaryote
Protozoan vs. Metazoan complex, starts as 1 cell.
divide (Mitoses) - daughter cells
become specialized

control of gene expression (in multicellular organism):
(1) different genes turned on in different cells (and at different times)
(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. 7.11) 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 9.
Second semester, we introduce the speculation that mitochondria (and chloroplasts), with their double membranes, are evolved from prokaryotes, engulfed into eukaryotic cells.

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 (Fig. 7.14)
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 (Fig. 7.23)
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

Cell junctions
Tight , Gap, Desmosome

This page was last updated 6/18/02

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