PL, plants; F, fungi; A, animals; mt, mitochondria; cp, plastid.
Table 1.2 Compartments of animal and plant cells and their main functions.
| Compartment | Occurrence | Functions | |
|---|---|---|---|
| Nucleus | A | P | Harbors chromosomes, site of replication, transcription, and assembly of ribosomal subunits |
| Endoplasmic reticulum (ER) | |||
| Rough ER | A | P | Posttranslational modification of proteins |
| Smooth ER | A | P | Synthesis of lipids and lipophilic substances |
| Golgi apparatus | A | P | Posttranslational modification of proteins, modification of sugar chains |
| Lysosome | A | Harbors hydrolytic enzymes, degrades organelles and macromolecules, macrophages eat invading microbes | |
| Vacuole | P | Sequestration of storage proteins, defense and signal molecules, contains hydrolytic enzymes, degrades organelles and macromolecules | |
| Mitochondrium | A | P | Organelle derived from endosymbiotic bacteria; contains circular DNA, own ribosomes; enzymes of citric acid cycle, β‐oxidation, and respiratory chain (ATP generation) |
| Chloroplast | P | Organelle derived from endosymbiotic bacteria; contains circular DNA, own ribosomes; chlorophyll and proteins of photosynthesis, enzymes of CO2 fixation and glucose formation (Calvin cycle) | |
| Peroxisome | A | P | Contains enzymes that generate and degrade H2O2 |
| Cytoplasm | A | P | Harbors all compartments, organelles, and the cytoskeleton of a cell; many enzymatic pathways (e.g. glycolysis) occur in the cytoplasm |
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
