Chapter 6: A Tour of the Cell
The study of cells has been limited by their small size, and so they were not seen and described until 1665, when Robert Hooke first looked at dead cells from an oak tree. His contemporary, Anton van Leeuwenhoek, crafted lenses; and with the improvements in optical aids, a new world was opened. Magnification and resolving power limit what can be seen. Explain the difference.
-Magnification: Ratio of an object's image size to its real size -Resolving power: Ability of the microscope to show detail
Which two domains consist of prokaryotic cells?
Archaea and Bacteria
The development of electron microscopes has further opened our window on the cell and its organelles. What is considered a major disadvantage of the electron microscopes?
Electron microscopes can not view live cells because the method of preparation is lethal.
Why are cells so small? Explain the relationship of surface area to volume.
Metabolic requirements of the cell sets upper limit on the size of the cell. The surface of the cell is where all of the nutrients/gas/signal exchange happens between the cell and extracellular environment. So the bigger the surface area, the better. However, the surface area of a cell decreases as it increases in volume. So, cells stay the small size they are to retain the greatest surface area possible in relation to their volume.
Describe how many neurons and intestinal cells each have greatly increased surface area.
Nerve cells have narrow, elongated shapes. Intestinal cells have microvilli, which have long thin projections in shape. This incereases SA w/o a big increase in volime
In cell fractionation, whole cells are broken up in a blender, and this slurry is centrifuged several times. Each time, smaller and smaller cell parts are isolated. This will isolate different organelles and allow study of their biochemical activities. Which organelles are the smallest ones isolated in this procedure?
Ribosomes
Study the electron micrographs in your text. Describe the different types of images obtained from: Scanning electron microscopy (SEM) Transmission electron microscopy (TEM)
SEM: SEM focuses a beam of electrons onto the surface of a specimen. Therefore, it displays a 3-D image of the sample's surface and its composition. TEM: TEM focuses a bean of electrons through a specimen. Therefore, it can display the internal structure of cells.
A major difference between prokaryotic and eukaryotic cells is the location of their DNA. Describe this difference.
The DNA of eukaryotes is in a bound nucleus. The DNA present in prokaryotes is in an unbound region called the nucleoid.
