1 Introduction to cell biology
1.1 Motivation
Why is the understanding of cell mechancis important? cells need to move and
interact with their environment ◦ cells have components that are highly dependent on
mechanics, e.g., structural proteins ◦ cells need to reproduce / divide ◦ to improve
the control/function of cells ◦ to improve cell growth/cell production ◦ medical appli-
cations ◦ mechanical signals regulate cell metabolism ◦ treatment of certain diseases
needs understanding of cell mechanics ◦ cells live in a mechanical environment ◦ it
determines the mechanics of organisms that consist of cells ◦ directly applicable to
single cell analysis research ◦ to understand how mechanical loading affects cells, e.g.
stem cell differentation, cell morphology ◦ to understand how mechanically gated ion
channels work ◦ an understanding of the loading in cells could aid in developing struc-
tures to grow cells or organization of cells more efficiently ◦ can help us to understand
macrostructured behavior better ◦ can help us to build machines/sensors similar to
cells ◦ can help us understand the biology of the cell ◦ cell growth is affected by stress
and mechanical properties of the substrate the cells are in ◦ understanding mechan-
ics is important for knowing how cells move and for figuring out how to change cell
motion ◦ when building/engineering tissues, the tissue must have the necessary me-
chanical properties ◦ understand how cells is affected by and affects its environment ◦
understand how mechanical factors alter cell behavior (gene expression) ◦ how differ-
ent cells interact with each other ◦ cell behavior may change under different conditions
(stress) ◦ to be able to study the extend of role of different parts of a cell in its behavior
◦ to predict cell behavior or response in different conditions ◦ movement/motility of
cell depends on mechanics ◦ load bearing, deformation of cells ◦ stability/integrity of
cell is provided by cytoskeleton and influenced by its mechanical properties ◦ to un-
derstand cells better ◦ to manipulate cells as we want ◦ to generate something based
on cell’s characteristis ◦ under physiological change, how does cell mechanics change
◦ provide guidance for cell manipulation ◦ extract cell properties from experiment ◦
observe cell response
1
, 1 Introduction to cell biology
1.2 Introduction to the cell
Cells are the fundamental building blocks of life. They are the smallest units of an
organism that can be characterized as living. Humans and many other organisms are
multicellular, i.e., they consist of multiple cells. Unicellular microorganisms, i.e., or-
ganisms consisting of one single cell such as bacteria, algae, and fungi, were the first
form of life on earth about 3-4 billion years ago. Robert Hooke was the first to use the
word cell in 1665, however, in the context of non-living cork. Antonie van Leeuwen-
hoek was the first person to ever observe a cell under a microscope in 1674. The cell
theory biologists use nowadays dates back to major contributions of Schwann and
Schleiden in 1839, enhanced by contributios of Virchow in 1858.
The basic elements of the classical cell theory state that
◦ all living things are composed of cells,
◦ cells are the basic unit of structure and function in living things, and
◦ cells are produced from other cells.
We can distinguish between two types of cells, prokaryotic cells, i.e., cells without a
nucleus such as bacteria, see figure 1.1, and eukaryotic cells, i.e., cells with a distinct
nucleus which possess organized chromosomes that store genetic material, see figure
1.2. In humans alone, there are more than 200 different cell types of different form and
function. Some characteristic numbers you might want to remember are the following:
◦ humans consists of approximately 100 trillion, i.e., 1014 cells,
◦ a typical cell size is 10µm
◦ smallest cells are less than 1µm in diameter while nerve cells can be up to a 1m long
◦ a typical cell mass is 1 nanogram.
It is characteristic for all biological cells to
bacterial capsule
flagellum cell wall
plasma membrane
cytoplasm
nucleoid
and ribosomes
in cytoplasm pili
Figure 1.1: Prokaryotic cell. Cell without a nucleus such as bacteria.
2
1.1 Motivation
Why is the understanding of cell mechancis important? cells need to move and
interact with their environment ◦ cells have components that are highly dependent on
mechanics, e.g., structural proteins ◦ cells need to reproduce / divide ◦ to improve
the control/function of cells ◦ to improve cell growth/cell production ◦ medical appli-
cations ◦ mechanical signals regulate cell metabolism ◦ treatment of certain diseases
needs understanding of cell mechanics ◦ cells live in a mechanical environment ◦ it
determines the mechanics of organisms that consist of cells ◦ directly applicable to
single cell analysis research ◦ to understand how mechanical loading affects cells, e.g.
stem cell differentation, cell morphology ◦ to understand how mechanically gated ion
channels work ◦ an understanding of the loading in cells could aid in developing struc-
tures to grow cells or organization of cells more efficiently ◦ can help us to understand
macrostructured behavior better ◦ can help us to build machines/sensors similar to
cells ◦ can help us understand the biology of the cell ◦ cell growth is affected by stress
and mechanical properties of the substrate the cells are in ◦ understanding mechan-
ics is important for knowing how cells move and for figuring out how to change cell
motion ◦ when building/engineering tissues, the tissue must have the necessary me-
chanical properties ◦ understand how cells is affected by and affects its environment ◦
understand how mechanical factors alter cell behavior (gene expression) ◦ how differ-
ent cells interact with each other ◦ cell behavior may change under different conditions
(stress) ◦ to be able to study the extend of role of different parts of a cell in its behavior
◦ to predict cell behavior or response in different conditions ◦ movement/motility of
cell depends on mechanics ◦ load bearing, deformation of cells ◦ stability/integrity of
cell is provided by cytoskeleton and influenced by its mechanical properties ◦ to un-
derstand cells better ◦ to manipulate cells as we want ◦ to generate something based
on cell’s characteristis ◦ under physiological change, how does cell mechanics change
◦ provide guidance for cell manipulation ◦ extract cell properties from experiment ◦
observe cell response
1
, 1 Introduction to cell biology
1.2 Introduction to the cell
Cells are the fundamental building blocks of life. They are the smallest units of an
organism that can be characterized as living. Humans and many other organisms are
multicellular, i.e., they consist of multiple cells. Unicellular microorganisms, i.e., or-
ganisms consisting of one single cell such as bacteria, algae, and fungi, were the first
form of life on earth about 3-4 billion years ago. Robert Hooke was the first to use the
word cell in 1665, however, in the context of non-living cork. Antonie van Leeuwen-
hoek was the first person to ever observe a cell under a microscope in 1674. The cell
theory biologists use nowadays dates back to major contributions of Schwann and
Schleiden in 1839, enhanced by contributios of Virchow in 1858.
The basic elements of the classical cell theory state that
◦ all living things are composed of cells,
◦ cells are the basic unit of structure and function in living things, and
◦ cells are produced from other cells.
We can distinguish between two types of cells, prokaryotic cells, i.e., cells without a
nucleus such as bacteria, see figure 1.1, and eukaryotic cells, i.e., cells with a distinct
nucleus which possess organized chromosomes that store genetic material, see figure
1.2. In humans alone, there are more than 200 different cell types of different form and
function. Some characteristic numbers you might want to remember are the following:
◦ humans consists of approximately 100 trillion, i.e., 1014 cells,
◦ a typical cell size is 10µm
◦ smallest cells are less than 1µm in diameter while nerve cells can be up to a 1m long
◦ a typical cell mass is 1 nanogram.
It is characteristic for all biological cells to
bacterial capsule
flagellum cell wall
plasma membrane
cytoplasm
nucleoid
and ribosomes
in cytoplasm pili
Figure 1.1: Prokaryotic cell. Cell without a nucleus such as bacteria.
2
