A
A, animal; P, plant.
A highly resolved tree of life is based on completely sequenced genomes (Ciccarelli 2006). The image was generated using Interactive Tree Of Life (iTOL) (Letunic 2007), an online phylogenetic tree viewer and Tree of Life resource. Eukaryotes are colored red, archaea green, and bacteria blue.
The most important biochemical and cell biological characters of Archaea, Bacteria, and Eukarya are summarized in Table 1.1.
As viruses and bacteriophages (Figure 1.3) do not have their own metabolism, they therefore do not count as organisms in the true sense of the word. They share several macromolecules and structures with cells. Viruses and bacteriophages are dependent on the host cells for reproduction, and therefore their physiology and structures are closely linked to that of the host cell.
Figure 1.3 Schematic structure of bacteriophages and viruses. (a) Bacteriophage T4 and (b) structure of a retrovirus (human immunodeficiency virus causing AIDS).
Eukaryotic cells are characterized by compartments that are enclosed by biomembranes (Table 1.2). As a result of these compartments, the multitude of metabolic reactions can run in a cell at the same time.
In the following discussion on the shared characteristics of all cells, the diverse differences that appear in multicellular organisms should not be forgotten. The human body has more than 200 different cell types, which show diverse structures and compositions. These differences must be understood in detail if cell‐specific disorders, such as cancer, are to be understood and consequently treated. Modern technology with Next‐Generation Sequencing (NGS) allows a study of single cells at a genomic and transcriptomic level.
Before a detailed discussion of cellular structures and their functions (see Chapters 3–5), a short summary of the biochemical basics of cellular and molecular biology is given in Chapter 2.
Progress in cell biology and biotechnology largely depends on innovative methods, as new methods often open windows to look deeper into biology and to solve old questions. Table 1.3 summarizes some of the important tools, which are important for cell and molecular biology today.
Table 1.3 Important methodological tools of modern biology.
| Problem | Technique/instrument | Remarks |
|---|---|---|
| Structure elucidation of proteins | Protein isolation, column chromatography (gel filtration, ion exchange, affinity) | Chapter 7 |
| Gel electrophoresis | Chapter 7 | |
| Protein–protein interactions (FRET, two hybrid systems, FRAP) | Chapters 19 and 23 | |
| Crystallization | ||
| X‐ray diffraction | ||
| NMR | ||
| Cryoelectron microscopy | ||
| Mass spectrometry | Chapter 8 | |
| Protein sequencing | ||
| DNA | PCR and quantitative PCR (qPCR) | Chapter 13 |
| DNA/RNA isolation | Chapter 9 | |
| DNA hybridization | Chapter 11 | |
| Sanger sequencing | Chapter 14 | |
| Restriction enzymes |