BelSU  Institute of Medicine Department Biomedical Sciences

1. Student's uniform
Форма студентов на лекции !

2. Biological Membrane
Physiology
Физиология биологической
мембраны
Lecture № 2
Topic:
Тема:
BelSU. Institute of Medicine.
Code and name of course
31.05.01 General Medicine
2019/2020 academic year
September 3, 2019

3. Guyton And Hall Textbook Of
Medical Physiology
P. 43–56.

4. • Guyton & Hall:
• Textbook of
• Medical Physiology
• -A South Asian Edition
PP. 9–11.

5. Biological Membrane
Definition
Oпределение термина
“биологическая мембрана”
Question No. 1

6. A biological membrane
• or biomembrane
• is an enclosing or separating membrane that
acts as a selective barrier, within or around
a cell.
• It consists of a lipid bilayer with
embedded proteins that may constitute close
to 50% of membrane content.

7. The Biological Membrane
• is a structure that separates various water
compartments in the body.
• The cell membrane is a biological membrane
that separates the cytoplasm from the
extracellular fluid.
• The organelle membrane is a biological
membrane that separates the cytosol from
the internal contents of the membrane
organelles.

8. • All biological membranes have the same
general structure.

9. Conceptual Model of The
Biological Membrane
Question No. 2

10. • In the year 1972 Singer and Nicolson
proposed a model for explaining the
membrane structure, taking into account
all the known facts.
• According to this model, cell membrane
consists of a highly viscous fluid matrix of
a bilayer of phospholipids having
globular proteins associated with them.
• This model came to be known as fluid
mosaic model.

11. • 1972 Singer and Nicolson
• fluid mosaic model
• bilayer of phospholipids + globular
proteins

13. Supported lipid bilayers (SLB)

14. Fibers of the
extracellular
matrix
Figure 5.12
Glycoprotein
Carbohydrate
(of
glycoprotein)
Microfilaments
of the
cytoskeleton
Phospholipid
Cholesterol
Proteins
CYTOPLASM
Glycolipid
Fluid mosaic model

15. polar
head
nonpolar
tails
P –
hydrophobic
molecules
hydrophilic
molecules
cytosol
1. Phospholipid bilayer
Plasma membrane components

18. The Membrane Proteins
Question No. 3

19. Membrane proteins
• are proteins that interact with
biological membranes.
• They are targets of over 50% of all modern
medicinal drugs.
• It is estimated that 20–30% of all genes in
most genomes encode membrane proteins.

20. Membrane proteins
• Integral membrane proteins
• Peripheral membrane proteins

21. Integral Membrane Proteins
• are permanently attached to the membrane.
• Such proteins can be separated from the
biological membranes only using detergents,
nonpolar solvents, or sometimes denaturing
agents.

22. Integral Membrane Proteins
• Integral monotopic proteins are associated
with only one layer of phospholipids. They
permeate only one layer of the phospholipid
bilayer.
• Integral polytopic proteins are associated
with two layers of phospholipids. They
permeate two layers of phospholipids several
times.

23. Peripheral membrane proteins
• are temporarily attached either to the lipid
bilayer or to integral proteins by a
combination of hydrophobic, electrostatic,
and other non-covalent interactions.
• dissociate following treatment with a polar
reagent, such as a solution with an elevated
pH or high salt concentrations.

28. • 3. Membrane Proteins - span entire
membrane or lie on either side
• Structural Support
• Recognition
• Communication
• Transport
Membrane proteinsMembrane proteins

29. Physical Model of The Biological
Membrane
Физические (Концептуальные)
Модели биологической мембраны
Question No. 4

30. Physical Models of The
Biological Membrane
• Flat
• Spherical

31. A Flat Physical Model of The
Biological Membrane

32. Black Lipid Membrane
• The earliest model bilayer system developed
was the “painted” bilayer, also known as a
“black lipid membrane”.
• First, a small aperture is created in a thin layer
of a hydrophobic material such as Teflon.
• Typically the diameter of this hole is a few
tens of micrometers up to hundreds of
micrometers.

33. Black Lipid Membrane
• To form a BLM, the area around the aperture
is first "pre-painted" with a solution of lipids
dissolved in a hydrophobic solvent by applying
this solution across the aperture with a brush,
syringe, or glass applicator.
• After allowing the aperture to dry, salt
solution (aqueous phase) is added to both
sides of the chamber.

35. A model lipid bilayer
• can be made with either synthetic or natural
lipids.
• The simplest model systems contain only a
single pure synthetic lipid.
• More physiologically relevant model bilayers
can be made with mixtures of several
synthetic or natural lipids.

36. A Spherical
Physical Model of The Biological
Membrane

37. A liposome is an artificially-prepared
vesicle composed of a lipid bilayer.

39. Biological Model of The
Biological Membrane
Биологические модели
биологической мембраны
Question No. 5

40. Biological Model of The Biological
Membrane
• erythrocyte membrane - erythrocytes after
hemolysis - shadows of erythrocytes

41. isotonic solution hypertonic solution hypotonic solution
10 microns
equal movement of water
into and out of cells
net water movement
out of cells
net water movement
into cells

42. Transport through a
biomembrane
Биологические модели
биологической мембраны
Question No. 6

43. How do molecules cross the plasma
membrane?
• Vesicular transport
• Passive transport
• Active transport

44. Vesicular transport
Везикулярный транспорт
Question No. 6.1

45. Vesicular transport

46. Exocytosis (out of the cell)
The fusion of a vesicle with the cell
membrane, releasing its contents to the
surroundings
Endocytosis (into the cell)
The formation of a vesicle from cell
membrane, enclosing materials near the
cell surface and bringing them into the cell
Vesicular transport

49. The different types of endocytosis

50. Receptor-mediated endocytosis

51. Mechanism of pinocytosis

52. Synaptic Vesicle Exocytosis
Экзоцитоз ы синапсах
Question No. 6.1.1

53. Kiss-and-run fusion
• is a type of synaptic vesicle release where the
vesicle opens and closes transiently. In this
form of exocytosis, the vesicle docks and
transiently fuses at the presynaptic membrane
and releases its neurotransmitters across the
synapse, after which the vesicle can then be
reused.

57. Coupling Endocytosis and
Exocytosis
Сопряжение эндоцитоза и
экзоцитоза
Question No. 6.1.2

61. exocytosis = vesicle fuses with the membrane and
expels its contents
Exocytosis and endocytosis
transport large molecules

63. Passive Transport Across
Membranes
Пассивный транспорт веществ
через мембрану
Question No. 7

64. • Small nonpolar molecules - simple diffusion
• Many molecules pass through protein pores by
diffusion through channels.
• Facilitated diffusion
Passive transport = diffusion across
membranes

65. • In passive transport,
substances diffuse
through membranes
without work by the
cell
EQUILIBRIUM
Molecule
of dye
Figure 5.14A & B
Membrane
EQUILIBRIUM

66. Relative permeability of a phospholipid
bilayer to various substances
Type of substance Examples Behaviour
Gases CO2, N2, O2 Permeable
Small uncharged polar
molecules
Urea, water, ethanol
Permeable, totally or
partially
Large uncharged polar
molecules
glucose, fructose Not permeable
Ions K+, Na+, Cl-, HCO3
- Not permeable

67. • Diffusion and gradients
– Diffusion = movement of molecules
from region of higher to lower
concentration.
– Osmosis = diffusion of water across a
membrane

68. Fick's laws of diffusion
• describe diffusion and can be used to solve for
the diffusion coefficient, D.
• They were derived by Adolf Fickin 1855.

71. • Effect of concentration
of a substance on rate
of diffusion through a
membrane by simple
diffusion and
facilitated diffusion.

72. • Osmosis causes cells to shrink in a hypertonic
solution and swell in a hypotonic solution
Water balance between cells and
their surroundings is crucial
osmoregulation = control of water balance

73. Facilitated diffusion

76. Michaelis-Menten saturation curve of
an enzyme reaction
An example curve with parametersVmax = 3.4 and Km = 0.4.

77. Michaelis–Menten kinetics
• In biochemistry, is one of the simplest and
best-known models of enzyme kinetics. The
model takes the form of an equation describing
the rate of enzymatic reactions, by relating
reaction rate v to [S], the concentration of a
substrate S. Its formula is given by

78. Michaelis–Menten kinetics

82. Leonor Michaelis
• 1875 – 1949
• a German biochemist,
physical chemist, and
physician,
• known primarily for
his work with Maud
Menten on enzyme
kinetics and Michaelis
-Menten kinetics in
1913.

83. Maud Leonora Menten
• 1879 – 1960
• a Canadian physician-
scientist
• Made significant contributions
to enzyme
kinetics and histochemistry.
• Her name is associated with
the famous Michaelis–Menten
equation in biochemistry

84. Active Transport Across
Membranes

85. Active transport
• is the movement of molecules across a cell
membrane in the direction against their
concentration gradient, i.e. moving from a low
concentration to a high concentration.
• is usually associated with accumulating high
concentrations of molecules that the cell needs,
such as ions, glucose and amino acids. If the
process uses chemical energy, such as from
adenosine triphosphate (ATP), it is termed
primary active transport.

86. Cotransport

88. Cotransport
• Protein-mediated transport of an ion or small
molecule across a membrane against a
concentration gradient driven by coupling to
movement of a second molecule down its
concentration gradient.

89. • Active
transport in
two solutes
across a
membrane
• Na+/K+
pump
• Protein
shape
change
Figure 5.18
Transport
protein
1
FLUID
OUTSIDE
CELL
First
solute
First solute,
inside cell,
binds to protein
Phosphorylated
transport protein
2 ATP transfers
phosphate to
protein
3 Protein releases
solute outside
cell
4 Second solute
binds to protein
Second
solute
5 Phosphate
detaches from
protein
6 Protein releases
second solute
into cell

90. Postulated mechanism of the
sodium-potassium pump

91. Electrogenic Nature of the Na+-K+
Pump
• The Na+-K+ pump moves 3 Na+ to the
exterior for every 2 K+ to the interior means
that a net of one positive charge is moved from
the interior of the cell to the exterior for each
cycle of the pump.
• Therefore, the Na+-K+ pump is said to be
electrogenic because it creates an electrical
potential across the cell membrane.

92. Active Transport Through Cellular
Sheets
• Substances must be transported all the way
through a cellular sheet instead of simply
through the cell membrane.
• Transport of this type occurs through the (1)
intestinal epithelium, (2) epithelium of the
renal tubules, (3) epithelium of all exocrine
glands, (4) and other epithelium sheets.

93. Active Transport Through Cellular
Sheets
The basic mechanism for transport of a
substance through a cellular sheet is
• (1) active transport through the cell
membrane on one side of the transporting
cells in the sheet,
• and then (2) either simple diffusion or
facilitated diffusion through the membrane
on the opposite side of the cell.

94. Active Transport Through Cellular
Sheets