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Ø Robert Hooke (1665) – was the first person to

study biological material

Ø Studied cork – dead cells

Ø Called the separate units cells

Latin: cellula=small compartments

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Ø Schleiden en Schwann (1838) – All organisms consist of cells and cell products

Ø Purkinje (1839) – introduced the term “protoplasm” for the living substance within cells

Ø Virchow (1858) – All cells arise from already existing cells, i.e. life comes from life (cell division)

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Ø The cell is the basic unit through which matter and energy are obtained, converted, stored and utilized

life occurs only in cells

Ø Cells are self-reproducing

cells originate from existing cells

Ø A specific relationship exists between structure and the function of a cell

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Ø Intake of raw materials (Absorption)

Ø Metabolism (Respiration & Synthesis)

Ø Growth in a programmed manner

Ø Respond to stimuli

Ø Homeostasis

Ø Reproduction

Ø Adaptation through evolution

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cells

Prokaryotes versusEukaryotes

The nucleus (chromatin,

chromosomes)

Replication, transcription, translation

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All cells, according to their internal organization, are divided in one of two groups

Prokaryotes (Pro= before a nucleus)

(All Bacteria are prokaryotes)

Eukaryotes (Eu= true; karyos= nucleus) Algae/other unicellular organisms (Kingdom:Protista) Fungi ( Kingdom:Fungi)

Plants (Kingdom: Plantae) Animals (Kingdom:Animalia)

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Ø Unicellular organisms – Bacteria, Cyanobacteria, Archaebacteria

Ø Small (0.5 – 3 µm) and primitive

Ø Plasmalemma, cell wall, capsule (not always)

Ø Flagellum

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Ø  Cytoplasm surrounded by a definite plasmalemma (cell membrane or plasma membrane)

Ø  No membrane-bound

organelles

Ø  But numerous ribosomes

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Ø Chromatin body consists of a network of

filaments

Ø Without a nuclear membrane (not delimited as

a unit)

Ø Area called the nucleoid

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Ø DNA exists in the form of a single circular

DNA thread (without any proteins)

Ø Treating the chromosome with the enzyme DNA-ase, the filaments disappear – thus DNA filaments

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Ø Some bacteria have small amounts of “extra”

DNA

Ø This extra DNA occurs as a circular plasmid

Ø Plasmids are used in genetic manipulation

Ø A desired gene (e.g. resistance against a

herbicide) can be transferred to the plasmid

Ø The plasmid is then transferred to the cell and

incorporated into the DNA of the plant cell

Ø The plant cell can now express the desired gene

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Ø  The only membranes in prokaryotes are systems of concentric membranes, the mesosomes

Ø  Originate as invaginations

of the plasmalemma

Ø  Respiratory enzymes most probably situated on the mesosome /plasmalemma

Ø  Mesosomes are also connected to the chromatin body

Ø  Probably plays a role in cell

division

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Ø Bacteria stained with iodine solution and rinsed

with alcohol

Ø If the stain remains – Gram-positive bacteria

Ø Cell wall relatively thick

Ø Consisting of only mucopeptides (peptidoglycans)

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Ø  Bacteria stained with iodine solution and rinsed with

alcohol

Ø  Stain is removed – Gram-negative bacteria

Ø  Cell wall relatively thin, but more complex

Ø  Inner layer of mucopeptides, outer layer of

phospholipids, proteins, lipopolysaccharides

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Ø The chemical composition of the cell wall determines the resistance of bacteria against antibiotics

Ø Penicillin prevents the synthesis of mucopeptides and is thus effectively used as a treatment against Gram-positive bacteria (walls containing only mucopeptides)

Ø But rather ineffective against Gram-negative

bacteria

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Ø  The capsule as a protective layer surrounding some

prokaryotic cells

Ø  Diplococcuspneumonia (causing pneumonia) has a capsule

not easily engulfed by white blood cells

Ø  Bacteria without a capsule are easily engulfed by white

blood cells

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Both possess DNA

2.

Both use the same genetic code and synthesize proteins employing mRNA, rRNA and tRNA

3.

Both have ribosomes and the ribosomes serve the same purpose in both

4.

Specific molecules, such as ATP and NAD+ have identical functions in both (Energy transfer)

These fundamental similarities indicate common

ancestors

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