Biology | Answers to Review Questions

Author Dr. George B. Johnson, Washington University
Author Dr. Peter H. Raven, Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer, Carleton College
Contributor Dr. Jonathan Losos, Washington University

Answers to Review Questions

Chapter 5 (p. 102)

1. (1) All organisms are composed of one or more cells. (2) Cells are the smallest living things. (3) Cells arise only from the division of other pre-existing cells.

2. There is an optimal surface-to-volume ratio; a big cell does not have enough surface area to interact properly for all its volume.

3. Prokaryotes contain peptidoglycan in their cell walls while eukaryotes do not; eukaryotic cells are characterized by possessing membrane-bounded organelles while the prokaryotes do not; and prokaryotes contain flagella composed of a simple fibrous protein, while eukaryotic flagella have a more complicated structure involving doublets and triplets of microtubules.

4. The endoplasmic reticulum is a bilayer lipid membrane. It compartmentalizes the cell interior and channels transport of molecules throughout the cell. Rough ER has ribosomes and synthesizes proteins; smooth ER does not have ribosomes and is involved in lipid synthesis and detoxification.

5. Golgi apparatus collects, package, and distributes cell-synthesized molecules. It is closely associated with the ER, which transports material to the Golgi.

6. Almost all eukaryotic cells contain mitochondria. In general, the more metabolically active the cell, the more mitochondria it will contain.

7. Chloroplasts carry out photosynthesis, the manufacture of carbohydrates from carbon dioxide and water with light energy.

8. Centrioles form the mitotic spindle between them during cell division (mitosis).

9. Actin protein filaments and tubulin microtubules are changeable, and intermediate fibers are stable.

10. Cilia and flagella have the same structure but cilia are shorter and more numerous.

11. The endosymbiont theory suggests that eukaryotes arose as a result of specific kinds of prokaryotic organisms living in association with one another: a photosynthetic organism perhaps invaded and started living within a non-photosynthetic organism. Evidence for this theory is the fact that chloroplasts and mitochondria have their own DNA.