agents
Abbreviations: SNP, single nucleotide polymorphism; GFP, green fluoresecnt protein; NGS, next generation sequencing.
References
1 Ciccarelli, F.D. (2006). Toward automatic reconstruction of a highly resolved tree of life. Science 311 (5765): 1283–1287.
2 Letunic, I. (2007). Interactive tree of life (iTOL): an online tool for phylogenetic tree display and annotation. Bioinformatics 23 (1): 127–128.
Further Reading
1 Alberts, B., Johnson, A., Lewis, L. et al. (2015). Molecular Biology of the Cell, 6e. New York: Garland Science.
2 Alberts, B., Bray, D., Hopkin, K. et al. (2019). Essential Cell Biology, 5e. New York: Garland Science.
3 Krebs, J., Goldstein, E.S., and Kilpatrick, S.T. (2018). Lewin's Genes XII. Burlington: Jones & Bartlett Learning.
2 Structure and Function of Cellular Macromolecules
Michael Wink
Heidelberg University, Institute of Pharmacy and Molecular Biotechnology (IPMB), Im Neuenheimer Feld 329, 69120 Heidelberg, Germany
In contrast to the diversity of life forms found in nature with several million species, the cells that make up all of these diverse organisms contain only a limited number of types of inorganic ions and molecules (Table 2.1). Among the most important macromolecules of prokaryotic and eukaryotic cells are polysaccharides, lipids, proteins, and nucleic acids, which are constructed from comparatively few monomeric building blocks (Table 2.2). The membrane lipids (phospholipids, cholesterol) will also be considered in this context because they spontaneously form supramolecular biomembrane structures in the aqueous environment of a cell.
Table 2.1 Molecular composition of cells.
| Contents | Bacterium (% of cell mass) | Animal cell (% of cell mass) |
|---|---|---|
| Water | 70 | 70 |
| Inorganic ions | 1 | 1 |
| Small molecules (sugars, acids, amino acids) | 3 | 3 |
| Proteins | 15 | 18 |
| RNA | 6 | 1.1 |
| DNA | 1 | 0.25 |
| Phospholipids | 2 | 3 |
| Other lipids | 7 | 2 |
| Polysaccharides | 2 | 2 |
| Cell volume (ml) | 2 × 10–12 | 4 × 10–9 |
| Relative cell volume | 1 | 2000 |
Table 2.2 Formation and function of the cellular macromolecules.
| Basic building blocks | Macromolecule | Function |
|---|---|---|
| Simple sugar | Polysaccharide | Structural substances: composition of the cell walls (cellulose, chitin, peptidoglycan); constituents of connective tissues |
| Storage substances: starch, glycogen | ||
| Amino acids | Protein | Enzymes: important catalysts for anabolic and catabolic reaction processes |
| Hemoglobin: O2 and CO2 transport | ||
| Receptors: recognition of external and internal signals | ||
| Ion channels, ion pumps, transporters: transport of charged or polar molecules across biological membranes | ||
| Regulatory proteins: signal transduction through protein–protein interactions | ||
| Transcription regulators: regulation of gene activity | ||
| Antibodies: recognition of antigens | ||
| Structural proteins: structural organization of supramolecular complexes | ||
| Cytoskeleton: formation of molecular networks in the cell that are important for shape and function | ||
| Motor proteins: muscle contraction | ||
|
Phospholipids,
|