Chapter 2
Cells and Biomembranes
Abstract Cell is constructed by various membrane structures called biomembrane,
and major components of the biomembrane are proteins and lipids. Biomembranes
have roles of compartmentation and selective permeation. Most of functions are
located on biomembranes. Physical properties such as fluidity, phase transition and
phase separation affect and regulate membrane functions. Functional role of cell
looks like a device of information processing; cell receives external stimulus by
receptor, transduces it and respond to the stimulus properly.
2.1 Cells and Biomembranes
Cell is an essential unit of life in living organisms including animals, plants, fungi
and bacteria on the earth. Although there is no strict definition of cell, cells have
common properties as follows.
1. Separated by envelope
2. Maintaining metabolism
3. Propagation by replication
4. Undergoing Darwinian evolution
5. Controlling cellular functions
Cell is composed of various biomembranes, and biomembranes have proteins and
lipids as their major components. Water molecules are indispensable for living
organisms, which is related to origin of life in ocean and physicochemical process
of biomembrane generation. Lipid components of biomembrane are called membrane lipids, and they include phospholipids, glycolipids and sterols. They have
amphiphilic property and, molecular shape and structure of assembly are shown in
(Fig. 2.1). In aqueous environment, lipid molecules assemble to form lipid bilayer
membranes. And proteins which are synthesized according to genetic information
are inserted into lipid membranes, and biological functions are added to
biomembrane. The cell is constructed by various membrane structures, such as
nucleus, mitochondria, endoplasmic reticulum (microsomes), lysosomes Golgi
© Springer Japan KK, part of Springer Nature 2018
K. Ohki, H. Miyata, Physical Principles of Biomembranes and Cells,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-4-431-56841-4_2
19
Cells and Biomembranes
Abstract Cell is constructed by various membrane structures called biomembrane,
and major components of the biomembrane are proteins and lipids. Biomembranes
have roles of compartmentation and selective permeation. Most of functions are
located on biomembranes. Physical properties such as fluidity, phase transition and
phase separation affect and regulate membrane functions. Functional role of cell
looks like a device of information processing; cell receives external stimulus by
receptor, transduces it and respond to the stimulus properly.
2.1 Cells and Biomembranes
Cell is an essential unit of life in living organisms including animals, plants, fungi
and bacteria on the earth. Although there is no strict definition of cell, cells have
common properties as follows.
1. Separated by envelope
2. Maintaining metabolism
3. Propagation by replication
4. Undergoing Darwinian evolution
5. Controlling cellular functions
Cell is composed of various biomembranes, and biomembranes have proteins and
lipids as their major components. Water molecules are indispensable for living
organisms, which is related to origin of life in ocean and physicochemical process
of biomembrane generation. Lipid components of biomembrane are called membrane lipids, and they include phospholipids, glycolipids and sterols. They have
amphiphilic property and, molecular shape and structure of assembly are shown in
(Fig. 2.1). In aqueous environment, lipid molecules assemble to form lipid bilayer
membranes. And proteins which are synthesized according to genetic information
are inserted into lipid membranes, and biological functions are added to
biomembrane. The cell is constructed by various membrane structures, such as
nucleus, mitochondria, endoplasmic reticulum (microsomes), lysosomes Golgi
© Springer Japan KK, part of Springer Nature 2018
K. Ohki, H. Miyata, Physical Principles of Biomembranes and Cells,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-4-431-56841-4_2
19