Bone and Cartilage – its Structure and Physical Properties - Biomechanics of Hard Tissues - page 32

Cross section of an animal cell

Cell membrane

Centrosome

Cytoplasm

Lysosome

Rough ER

Nucleus

Nucleolus

Smooth ER

Nuclear
membrane

Ribosomes

Vacuole

Golgi body

Mitochondrion

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Figure 1.19 An animal cell. Peptide chains,
alpha-1 and alpha-2 chains, known as pre-
procollagen, are formed during translation
on ribosomes along the rough endoplas-
mic reticulum (Rough ER, RER) inside the
cell. Triple helical structure is formed inside

the endoplasmic reticulum from each two
alpha-1 chains and one alpha-2 chain. Pro-
collagen is shipped to the Golgi apparatus,
where it is packaged and secreted by exocy-
tosis. After [129].

Leeuwenhoek [91 ] pointed out an analogy between the structures of bone
and wood. This analogy is almost apparent and shows how different methods
are developed by the nature to reach the same goal, in our case: resistance and
moderate stiffness. Similar opinion was expressed by Monceau (1700-1782), a
botanist and agronomist.
The bones have to support the body of vertebrates and the tree trunk with
branches has to support the weight of a plant, cf. [136]. These similar mechanical
requirements lead at first sight to similar solutions, known as homoplasy .Thestem
of a plant is built from large cells. Every cell of the plant has a rigid cover - the
cellulose wall, in distinction from animal cell. Therefore, the skeleton of a plant
itself is composed of cells. The internal geometry of the bone resembles the
geometry of the trunk. It is built from a rigid material and it is partitioned into
(cellular in general meaning) structures, but this hydroxyapatite structure does not
belong to the bone cells (osteocytes). Moreover, while all parts of the bone are
active, in the stem of a vascular plant, only the phloem with cambium situated
under the bark is the living tissue.

1.3.4.2 Cell Membrane
Amphiphile (Gr.

, philia: love, friendship) is a
term describing a chemical compound possessing both hydrophilic ( water-loving)

αµφις , amphis: both and φιλ ı α