BIOLOGY (Lecture 3)
MEMBRANE and DIFFUSION
(part I – creating of membrane
and passive transport)
Primitive „border structure“ 4 billions years ago -- in water
…space IN and space OUT
(nanometers/micrometers)
• Protobionta / Liposomes
Archaic sea and lakes
• Exact fossil arguments:
Some additional interesting notes about special literature of
early life and biological membrane (will not be in exam test) :
DEAMER, David W.; PASHLEY, R. M. Amphiphilic components of the
Murchison carbonaceous chondrite: surface properties and membrane
formation. Origins of Life and Evolution of the Biosphere, 1989, 19.1: 21-38.
Evidence for early life in Earth's oldest hydrothermal vent precipitates
MS Dodd, D Papineau, T Grenne, JF Slack, M Rittner… - Nature, 2017 -
https://www.nature.com/articles/nature21377?source=post_page------------
---------------
Cappellen, P. V. & Berner, R. A. A mathematical model for the early diagenesis of
phosphorus and fluorine in marine sediments: apatite precipitation. Am. J. Sci. 288,
289–333 (1988)
[HTML] Did cyclic metaphosphates have a role in the origin of life?
T Glonek - Origins of Life and Evolution of Biospheres, 2021 - Springer
Da Silva JAL, Holm NG (2014) Borosilicates and silicophosphates as
plausible contributors to the origin of life. J Colloid Interface Sci 431:250–
254. http://www.sciencedirect.com/science/article/pii/S0021979714001179
.
Border structure
…space IN and space OUT
Recent animal and plant border structure –
is called MEMBRANE. And key components
are lipids…
• The phospholipids are the critical
units of the cell membranes
protecting the cells. These units
are also responsible for the
sustainability of the cells. The
inflow and outflow of different
biomolecules are controlled by
the cell membrane. In fact, these
units also host a flexible gate for
the entry and exit of the organic
molecules.
• Due to the excellent structure, the
prime phospholipid function is a
selective passage.
• . These units are also floating and
moving. It gives the cell
membrane a quasi-fluid
structure letting them execute
this function. The cell
membranes have specific
channels for various organic
compounds such as proteins,
fats, steroids, carbohydrates, etc.
*Extra note*
PHYSICS of DIFFUSION
• Before desription of biological function
of membranes, we will made some on 4 pages extra
physical description of diffusion and concentration
eqprincips.
(Some of students could have some theory in
previus high school study, some not)
DIFFUSION in simple basin
(without any membrane)
• Red molecules are droped to water.
What will be happen?
later and finaly
concentration of RED and WATER
are finaly homogenous
• Why RED and WATER molecule diffuse?
there exist place with high concetration and
near place with low concentration . This gradient of concentation caused the molecule movement
This movement is quantified by FICK LAW
where S is the “contacting area of drop (area with red molecules)“
D is special physical constant for this type of molecules (will be shown
in next pages)
grad is gradient of concentration in place A and place B
(if concentration is the same, there is gradient = 0 and no movement of molecules)
Area A Area B
• However the same situation can be seen
also from oposite site of view:
ALSO WATER MOLECULES are driven from place B (high concentration of WATER to A (low
concentration of water)
DIFFUSION in basin
with the membrane
Variant 1: Membrane is permeable only for RED
THE PHYSICAL FORCE FOR MOVEMENT OF RED MOLECULES are the same like in
basin withou membrane.
Concentration of RED and WATER will be finaly homogenous in both compartments.
Variant 2: Membrane is permeable only for WATER
Water is moving through the membrane and „wants to made“ oncentration of „RED
so much low as possible“ (idealy press to zero = total water).
In some time it is stoped in equilibrium (because of extarnal hydrostatic pressure)
Prectical example
• Diffusion of
sugar molecules to pure water water molecules to high concentrated sugar compartment
• Diffusion of oxygen molecules
Practical example
• Homework:
Why bears body will be grow in water ?
Can you arranged the chemical to change
the bear body volume back?
The End of
*Extra note*
PHYSICS of DIFFUSION