Biomedical Engineering Reference
In-Depth Information
Nuclear pore
Ribosomes
Endoplasmic reticulum
Centrosomes with pair of centrioles
Microtubules
Mitochondria
Chromatin network
(DNA)
Nuclear membrane
Nucleus
Nucleolus
Lysosome
Golgi apparatus
Intermediate filaments
Plasma membrane
Actin filaments
Vesicles
Extracellular matrix
Figure 1.1
Animal cell and its internal organization.
Plasma Membrane
The plasma membrane forms the outermost boundary of the cell, enclosing the
cytosol and organelles. The membrane is made up of a phospholipid bilayer with
embedded proteins. It is a quasi-fluid structure where the membrane glycoproteins, in
addition to serving as channels for transport of specific molecules, are also involved
in physical interaction with other cells, as well as in signal transduction. The carbo-
hydrate moieties in the cell membrane are mostly linked with the proteins and lipids,
giving rise to glycocalyx on the outer side of the cell, which imparts the characteristic
negative surface charge to the cell. Although all biomembranes have the same basic
phospholipid bilayer structure and certain common functions, each type of cellular
membrane also has certain distinctive activities determined largely by the unique set
of proteins associated with that membrane.
Cytoplasm
Enclosed inside the plasma membrane is the cytoplasm—which can further be cat-
egorized as cytosol and the organelles. The organelles include the nucleus, mito-
chondria, peroxisomes, endoplasmic reticulum (ER), Golgi body, endosomes, and
lysosomes. The cytosol is the liquid phase in which the organelles are suspended,
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