1. See Table 4.3.
2. Compare with Figure 4.11.
3. For the particulars of bacterial (prokaryotic) and human (eukaryotic) cell structure, see Table 4.1. The virus consists only of a nucleic acid core and protein capsids. In some cases an envelope is also present.
4. Archaean cells were discovered in the late 1970's. These cells defied placement in the existing "two life form" system because they possessed characteristics of both prokaryotic and eukaryotic organisms. Our knowledge of this third life form is still evolving.
5. Every cell must have an energy source, a site for protein synthesis, methods of taking in and giving off metabolic products. Thus, the cells must all have the same basic organelles. Form and function are dictated by the genes. Not all genes are functional in all cells. Thus, cells may have different external appearances and may specialize in the production of different products.
6.
| Surface | Volume | Ratio | |
|---|---|---|---|
| Formula | 6s2 | s3 | S/V |
| 3 cm | 54 cm | 27 cm | 54/27 |
| 5 cm | 150 cm | 125 cm | 150/127 |
| 7 cm | 294 cm | 343 cm | 294/343 |
7. See Table 4.1.
8. A virus has a nucleic acid core (RNA or DNA), a protein coat, and sometimes an envelope. A viroid is a highly wound strand of RNA. A prion is an abnormal form of a glycoprotein. (More detailed answers are possible.)
9. The capsid often consists of many copies of the same protein.
10. The classic cell theory is that the cell is the basic unit of life. The cell theory today is the ongoing evolution of our understanding of the structure and function of the basic components of the cell. The endosymbiont theory is the theory that the mitochondrion and the chloroplast were once free-living prokaryotes that were "captured" by other cells
TO THINK ABOUT
1. The liver cell is probably more efficient than the pancreas cell because of the surface/volume ratio. 110,000/5000 = 22 (liver) to 13,000/1000 = 13 (pancreas). If the entire organ is considered, students might ask which organ has the most cells or how many cells are engaged in which functions. In that case, either answer could be correct.
2. Division of labor adds to increased efficiency.
3. The lysosomes do not contain the enzymes necessary for the effective dismantling of glycogen. Thus, the glycogen builds up.
4. Muscle cells need additional energy as supplied by the mitochondria. White blood cells, the body's scavengers, need the digestive enzymes found in the lysosomes.
5. This experiment traces the functional continuum of the cellular organelles. To use a similar technique to follow the lysosome's activities, one might tag a substance that would be engulfed by a cell. The chemical dismantling could then be traced. Other answers are possible.
6. This observation supports the endosymbiont theory because the endosymbiont theory states that the mitochondrion and chloroplast were originally symbiotic prokaryotes.
7. The answer could be either "yes" or "no." If "yes", the path would be ER to Golgi to vesicle to mitochondrion. If "no", the argument would be that the mitochondrial DNA more closely resemble the DNA of prokaryotes than the DNA of eukaryotes. An additional "no" argument would be that the mitochondrial membrane would probably be impermeable to the nuclear DNA.
8. Viruses do not possess all characteristics of life.
9. Answers will vary.
10. Answers will vary.
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