Body Fluid
•
Transport Processes
Anatomy and Physiology Text and Laboratory
Workbook, Stephen G. Davenport, Copyright 2006, All
Rights Reserved, no part of this publication can be
used for any commercial purpose. Permission requests
should be addressed to Stephen G. Davenport, Link
Publishing, P.O. Box 15562, San Antonio, TX, 78212
All the cells of the body are linked together
by body fluid. This fluid serves as the transport
medium for oxygen, carbon dioxide, nutrients,
wastes, hormones, electrolytes, antibodies, etc.
• Cells organize the body into two anatomic fluid
compartments, the
– (1) intracellular and the (2) extracellular
compartments.
• In order for fluids to enter the body and to move
from compartment to compartment, they must
pass through the plasma membranes of cells.
Intracellular Fluid Compartment
Anatomical Fluid
Compartments
• The intracellular fluid compartment is the
compartment formed by all of the spaces within
the cells of the body, and it contains
intracellular fluid (ICF).
• Intracellular fluid accounts for about 63% of the
body’s total fluid.
The two anatomical fluid compartments
of the body are the intracellular and
extracellular compartments.
Fig. 5.1
Extracellular Fluid Compartment
• The extracellular fluid compartment is the
compartment consisting of the spaces
surrounding the cells of the body, and it contains
extracellular fluid (ECF).
• The two major divisions of the extracellular
compartment are the
Interstitial Compartment
•
The Interstitial Compartment consists of the
microscopic spaces, the interstices, among
adjacent cells. The interstitial compartment
contains interstitial fluid. Interstitial fluid accounts
for about 30% of the body’s total fluid volume.
– (1) interstitial compartment and the (2) intravascular
compartments.
– These extracellular fluid compartments function to
maintain the normal fluid volume and chemical
concentration of the intracellular compartment.
Fig. 5.2
1
Intravascular Compartment
• The Intravascular Compartment consists of the spaces
within the body’s blood and lymphatic vessels. Its fluid
accounts for about 7% of the body’s total fluid volume.
Plasma is the fluid component of blood, and lymph is the
fluid component of the lymphatics.
Fig. 5.4
Photograph of developing adipose tissue with blood vessels
showing extracellular and intracellular compartments (430x).
Fig. 5.3
Transport Processes
• Transport across the plasma membrane is by passive
and active processes.
– Passive movement processes do not directly require the
expenditure of energy (ATP) by the cell, whereas active
processes do.
• Passive processes include simple diffusion, facilitated
diffusion, osmosis, and dialysis and filtration.
• Active processes include transport processes across the
plasma membrane. Two active transport processes are
ATP driven membrane proteins that include carrier
proteins and solute pumps and ATP driven vesicular
(bulk) transport processes such as endocytosis and
exocytosis.
Solution
A mixture is produced when two or more
components are physically combined and
which retain their own properties. Three
common mixtures include solutions,
colloids, and suspensions.
Colloid
• A solution is a
homogeneous mixture
(has uniform composition
throughout) formed by
dissolving a solute (solid,
liquid, or gas) in a solvent
(liquid, usually water). A
solution is described as a
single-phase system.
– A solute is the substance
that is dissolved by the
solvent.
– A solvent is the substance
that dissolves the solute
and is usually present in
the greater amount.
MIXTURES
Fig. 5.5
• A colloid mixture contains
solutes or larger particles
(macromolecules to
microscopic in size) than
those of a solution but not
so large as to settle out
(as in a fine suspension).
Usually, the particles
interfere with the
transmission of light and
cause light to scatter.
• Typically, when a colloid
consists of a substance
such as starch or gelatin,
and the solvent is water,
the resulting colloidal
mixtures are of a
gelatinous or gel
consistency
Fig. 5.6
2
Suspension
• A suspension is a mixture
that contains particles
larger than those of a
colloid.
• A suspension is
considered to be a twophase system where a
solid phase (fine
particles) is intermixed
with a liquid phase
(water). Typically, over
time the phases separate
and the solids (particles)
settle out.
Lab Activity 1 –
Molecular and Particle Movement
This lab activity is
designed to visually
demonstrate
molecular and particle
movement resulting
from kinetic energy.
Fig. 5.9
Fig. 5.7
India Ink Movie
Milk’s Brownian Motion Movie
Passive Movements
PASSIVE MOVEMENT
ACROSS THE PLASMA
MEMBRANE
• The plasma membrane is a selectively
permeable membrane that surrounds the cell.
The passive movement of water and dissolved
substances across the membrane requires
permeability through the membrane.
• Passive processes that allow permeability are
diffusion and filtration.
– Processes of diffusion are simple diffusion, facilitated
diffusion, osmosis, and dialysis.
– Osmosis, the diffusion of water across a selectively
permeable membrane, and dialysis, the separation of
solutes by a selectively permeable membrane, are
processes that utilize simple diffusion.
3
Diffusion
•
Diffusion is a process of equalization which involves
movement from an area of high concentration to an
area of low concentration (along a concentration
gradient).
•
Net diffusion is a measurement of how much
equalization occurs. The greater the difference in
concentrations (concentration gradient), the greater the
equalization (net diffusion).
•
The driving force for equalization is molecular
motion. Molecular motion is described as disordered
and is associated with molecular internal energy, the
microscopic energy on the atomic and molecular scale.
Temperature
•
Temperature is a measure of the
kinetic energy associated with the random
microscopic motion of atoms and
molecules. Increasing the temperature
results in an increase of molecular motion
and the rate of diffusion. Decreasing the
temperature decreases the rate of
molecular motion and the rate of diffusion.
Size
• The size of the molecules infers that larger
molecules have more mass, offer more
resistance, and move slower than smaller
molecules (when in the same system of
internal energy). Thus, in the same
environment larger molecules diffuse at a
slower rate than smaller molecules.
Diffusion
• The rate of diffusion is how fast the molecules
move through their environment.
• The movement of molecules (and particles)
through their environment is influenced by
– (1) kinetic energy (temperature),
– (2) the nature of the environment (gas, liquid, or solid)
and
– (3) the size of the molecules (and particles), and
– (4) electrical charge.
Environment
• The nature of the environment relates to
the permeability of the molecules for the
environment. Molecules move faster
through environments of increasing
permeability and slower through
environments of decreasing permeability.
Charge
• Molecules with electrical charges interact
with other charged molecules in the
environment. Molecules and atoms having
opposite charges are attracted one to
another, and molecules and atoms having
the same charge are repelled. Thus, a
positively charged substance would diffuse
faster into a negatively charged
environment than into a positively charged
environment.
4
Lab Activity 2 –
Molecular Movement and Weight
Fig. 5.10
Fig. 5.11
Consider the influence of temperature, size, environment, and charge.
• In a mixture (of equal temperature), all the
molecules or particles are subjected to the same
amount of internal energy. Since influenced by
the same amount of energy, the smaller particles
(less mass) move faster than the larger particles
(more mass).
• This activity studies the influence of size (weight)
on the rate of diffusion. The diffusion of
methylene blue (molecular weight of 320) is
compared to the diffusion of potassium
permanganate (molecular weight of 158).
Fig. 5.15
Fig. 5.13
Fig. 5.12
Fig. 5.14
Simple Diffusion
• Permeability of the substance may be due to
– solubility in the membrane’s phospholipid bilayer,
– the presence of membrane channels, or
– The presence of carrier proteins.
Simple Diffusion Across the
Plasma Membrane
•
Diffusion is a process of equalization which
involves movement from an area of high
concentration to an area of low concentration
(along a concentration gradient).
Generally, substances are soluble in the
phospholipid bilayer of the plasma membrane if
they are small, nonpolar, and lipid soluble.
Substances such as oxygen and carbon dioxide
easily diffuse through the phospholipid bilayer
the plasma membrane.
5
Lipid Solubility
Fig. 5.17
Lipid solubility allows small nonpolar molecules such as oxygen
and carbon dioxide to diffuse through the plasma membrane.
Diffusion follows a concentration gradient, from high to low.
Membrane Channels
Fig. 5.18
Membrane channels allow the diffusion of specific substances across
the plasma membrane. Diffusion always follows a concentration
gradient, from high to low.
Facilitated Diffusion
• Facilitated diffusion
utilizes carrier proteins
that participate in the
movement of the
substance across the
membrane. An
interaction of the
membrane proteins with
the diffusing substance
causes the membrane
proteins to transport the
substance across the
membrane.
• Facilitated diffusion
typically involves the
diffusion of large
molecules, such as the
facilitated diffusion of
glucose into the cell.
MOVEMENT OF WATER BY
HYDROSTATIC PRESSURE
Hydrostatic pressure is the
pressure of water against a wall or
membrane.
Fig. 5.19
Sources of Hydrostatic Pressure
•
Three of the sources of hydrostatic
pressure in our body are the
– contraction of the heart (blood pressure),
– osmotic movement of water (water volume
changes), and
– gravity (such as venous blood pooling in the
legs of a standing individual).
Blood (hydrostatic) pressure
• Blood (hydrostatic)
pressure is the driving
force for the
movement of water
and various solutes
from blood vessels
called capillaries into
the interstitial spaces.
Fig. 5.3
6
Filtration
Osmosis
•
• The osmotic movement of water facilitates water
flow from one area to another. Osmosis is
essential in interstitial water reabsorption at the
capillaries and water reabsorption by the
kidneys.
• Net water movements cause changes in the
shape of cells, in pressure, and the location of
water (interstitial vs intracellular environments).
Filtration is the forced movement of a
substance through a filter.
– A filter is a porous substance or structure
used to separate suspended material in
liquids or gases.
– Filtration requires a driving pressure to force
the liquid or gas through the filter.
– The pore size of the filter determines which
materials will pass through.
– The product of fluid filtration is called a filtrate.
Lab Activity 3 – Filtration
Lab Activity 3 – Filtration
What are the test results for
filtration of solution of
copper sulfate and
starch? What determined
passage through the
membrane?
Fig. 5.20
A setup for a filtration apparatus and expected results due to pore size of
filter paper.
Fig. 5.21
Filtration at the Plasma Membrane
Filtration at the Plasma Membrane
The plasma membrane contains protein
channels that function as pores and is
selectively permeable.
– Selective permeability means that the plasma
membrane “selects” what substances can
pass through because the size of its pores or
other physical characteristics of the
membrane.
Fig. 5.23
Blood pressure provides the driving force for filtration at the capillary.
Filtration is one way fluid and solutes are delivered into the interstitial
spaces (forming interstitial fluid) to support cellular metabolism.
7
Filtration at the Plasma Membrane
MOVEMENT OF WATER BY
OSMOSIS
Osmosis is the diffusion of water
through a selectively permeable
membrane such as the plasma
membrane.
Fig. 5.24
Fenestrated glomerular capillaries in the kidney produce plasma filtrate.
The filtrate passes through a series of tubes where it is modified by
reabsorption (and secretion) into urine.
OSMOSIS
OSMOSIS
• Osmosis is the diffusion of water through a
selectively permeable membrane such as the
plasma membrane.
• Water diffuses through the lipid bilayer of the
plasma membrane and through plasma
membrane water channels called aquaporins.
• Net water movement occurs when the
concentration of a solute that is impermeable to
the plasma membrane differs between the
intracellular and the extracellular fluid.
OSMOSIS
In this illustration, the
extracellular fluid contains
a higher concentration of
impermeable solutes than
the intracellular fluid.
Thus, the extracellular
fluid has a lower
concentration of water,
and there is net water
diffusion out of the cell.
• A difference in impermeable solute concentrations
means that there is a difference in water
concentration, and net water movement is from the
region of higher water concentration to the region of
lower water concentration.
• Water osmotically moves out of a cell when the
extracellular fluid has less water (because it has more
impermeable solutes) than the cell. In this case, the
movement of water out of the cell causes the cell to
shrink because the cell’s water (hydrostatic) pressure
decreases.
Effects of Osmotic SolutionsOsmolality and Tonicity
Osmolality
– The osmolality of a solution is a measure of
the number of particles present in the
solution, regardless of the size or weight of
the particles.
– To be osmotically effective, the particles must
be impermeable to the membrane and at
different concentrations on each side of the
membrane.
Fig. 5.25
8
Osmolality and Permeability
• The osmolality of a
solution is a measure of
the number of particles
present in the solution
• If, as shown in this
illustration, both the
solute (Na+ and Cl-) and
the solvent (water) is
permeable to the
membrane, there is no
osmotic effect. Both the
solute and the solvent
(water) reach equilibrium.
Tonicity
• Tonicity
– Tonicity is the “effective
osmolality,” and is the sum
of the solutes that have the
ability to affect the
movement of water across
a selectively permeable
membrane. In the
consideration of osmolality
of a solution, both particles
that are permeable and
impermeable to the cell
membrane are considered.
Fig. 5.27
Fig. 5.26
Tonicity
• Tonicity only considers
the particles that are
“osmotically effective,”
Osmotic pressure
Osmotic pressure is the pressure exerted
by the movement of water through a
selectively permeable membrane that
separates two solutions with different
concentrations of solute.
– the particles that are
impermeable, and
– have the ability to affect
water movement across
the membrane.
Fig. 5.28
– A solution’s osmotic pressure is proportional
to the solution’s concentration of membrane
impermeable solutes.
Osmotic pressure
• Osmotic pressure
results because of the
osmotic movement of
water and is
measured
(expressed) as the
pressure required to
oppose the water’s
movement.
Tonicities of Solutions
There are three possible tonicities of
solutions:
–isotonic,
–hypotonic, and
–hypertonic.
Fig. 5.29
9
Isotonic Solution
•
An isotonic solution is a solution that
has the same concentration of
impermeable solutes as within the cell.
– Equal concentrations of impermeable solutes
means that there are equal concentrations of
water.
– There is no net diffusion of water and no
change in hydrostatic pressure.
Hypotonic Solution
•
A hypotonic solution is a solution that
has a lower concentration of impermeable
solutes than within the cell.
– Since the solution has a lower concentration
of solutes, it has a higher concentration of
water, and net water diffusion is into the cell.
– Water movement into the cell increases its
hydrostatic pressure.
Hypertonic Solution
•
A hypertonic solution is a solution that
has a higher concentration of solutes than
within the cell. Since the solution has a
higher concentration of solutes, it has a
lower concentration of water, and net
water diffusion is out of the cell.
• There is no net
diffusion of water and
no change in
hydrostatic pressure.
– Animal cells maintain
a normal shape.
– Plant cells maintain
normal turgor, the
normal state of
distension of the cell
and wall.
Fig. 5.30
Hypotonic Solution
• Cells bounded by only
their plasma membranes,
such as animal cells,
increase in size (swell)
and may rupture (lysis).
• Plant cells, bounded by
cell walls, have an
increase of turgor, the
normal state of distension
of the cell and wall. The Fig. 5.31
plant tissue becomes firm
and rigid.
Hypertonic Solution
• Cells bounded by only
their plasma membranes,
such as animal cells,
decrease in size (shrink).
• Plant cells, bounded by
cell walls, have a
decrease of turgor, the
normal state of distension
of the cell and wall, and
the plasma membranes
pull away from their walls.
The cells shrink, and the
plant tissue becomes soft
and pliable.
Fig. 5.32
10
Osmometer – Thistle Tube
Lab Activity 4 – Osmometer
An osmometer is a device used to
measure osmotic force
• A typical laboratory
osmometer and setup
for laboratory
demonstration is
shown in this
illustration.
• In this illustration the
solution surrounding
the membrane is
________ and water
moves (into / out of)
the thistle tube.
Fig. 5.33
Semi-permeable Membrane
Lab Activity 5 –
Osmosis and Red Blood Cells
Fig. 5.34
Isotonic Solution - Red Blood Cells
A normal (isotonic)
saline solution is 0.9%
NaCl.
• Red blood cells in a
isotonic solution have
normal shape and size.
– Each red blood cell is a
biconcave disc with a
thin central region
Fig. 5.37
Hypertonic Solution - Red Blood Cells
A hypertonic solution has
a higher concentration of
solutes than within the
cell.
• Since the solution has a
higher concentration of
solutes, it has a lower
concentration of water,
and net water diffusion is
out of the cell.
• Water movement out of
the cell decreases its
hydrostatic pressure, and
the cell shrinks. Red
blood cells in a hypertonic
solution are crenated.
Fig. 5.39
11
Hypotonic Solution - Red Blood Cells
• A hypotonic solution has
a lower concentration of
solutes than within the
cell.
• Since the solution has a
lower concentration of
solutes, it has a higher
concentration of water,
and net water diffusion is
into the cell.
• Water movement into the
cell increases its
hydrostatic pressure, and
the cell swells.
Lab Activity 6 –
Osmosis and Potato Cells
Fig. 5.41
Isotonic Solution - Potato Cells
• Potato cells have a
slightly flexible wall
bounded internally by the
plasma membrane.
Turgor pressure (water
pressure) of the
cytoplasm maintains the
normal state of distension
of the cell wall. Osmotic
changes that result in an
increase or a decrease of
water volume change the
cell’s turgor.
Hypotonic Solution - Potato Cells
• Distilled water is
hypotonic to the potato. In
a hypotonic solution,
water diffuses into the
cells of the potato and
their turgor pressure
increases. Increased
turgor pressure results in
increased rigidity of the
potato slice.
Fig. 5.42
Fig. 5.43
Hypotonic Solution - Potato Cells
Hypertonic Solution - Potato Cells
The 10%NaCl solution is
hypertonic to the potato.
In a hypotonic solution,
water diffuses out of the
potato cells and their
turgor pressure
decreases. Decreased
turgor pressure results in
decreased rigidity of the
potato slice.
Fig. 5.44
Fig. 5.46
Fig. 5.43
12
Hypertonic Solution - Potato Cells
Hypotonic & Hypertonic Solutions
• Reversing the
solutions reverses
the osmotic effect.
Plasmolyzed cells
become rigid, and
rigid cells become
plasmolyzed.
Fig. 5.45
Fig. 5.44
Fig. 5.46
Normal Turgor
Lab Activity 7 –
Osmosis and Elodea
Fig. 5.50
Fig. 5.49
Elodea cells with normal turgidity. The plasma
membranes are not seen because they are in
intimate contact with the cell walls.
Hypertonic Solution - Elodea
• Plasmolysis occurs
when plant cells are
placed in an osmotic
solution that promotes
the outward
movement of water.
As cytoplasmic water
loss occurs, spaces
form between the
plasma membranes
and the cell walls.
Fig. 5.53
13
Hypotonic Solution - Elodea
• A hypotonic or an isotonic solution will produce
normal turgor pressure in a plant cell. Turgor
pressure is limited by the non-flexible cell wall.
• A plasmolyzed cell subjected to a hypotonic
solution will show an increase of turgor
pressure
Hypotonic Environment
Lab Activity 8 Osmosis and Paramecium
• The unicellular Protozoa that live in fresh water, such as
Paramecia and Amoebas, live in a hypotonic
environment.
• The hypotonic environment results in continued
MOVEMENT of fluid into the organism.
• Organelles called contractile vacuoles eject excess fluid
from the organism maintaining cytoplasmic osmolarity
(solute concentration).
Fig. 5.57
14
DIALYSIS
Dialysis is the separation of solutes
according to their size by diffusion through a
selectively permeable membrane. Depending
upon the size of the pores of the membrane,
solutes will either diffuse across the membrane or
be restricted by their size.
Dialysis Membrane
Lab Activity 9 Osmosis and Dialysis using
Dialysis Tubing (membrane)
• Dialysis is the
separation of solutes
according to their size
by the utilization of a
selective permeable
membrane. Solutes
that are small enough
to diffuse through the
membrane’s pores
are separated from
the larger solutes.
Fig. 5.58
OSMOSIS USING
DIALYSIS MEMBRANE
DIALYSIS USING
DIALYSIS MEMBRANE
Which solute/s passed through the
dialysis membrane?
If a solute passed through the
membrane, it would seem that the
dialysis bag would lose weight.
However, the dialysis bag gained
weight – explain this event.
Fig. 5.62
Fig. 5.60
Which line (in any) most correctly
matches the change in weight of the
bag?
Fig. 5.64
Fig. 5.66
15
Osmosis
(using membranous egg)
Lab Activity 10 Osmosis and Dialysis using
Membranous
(Unshelled) Egg
• This activity
demonstrates
osmosis by the
change in weight of
the egg. The egg
contains a high
concentration of
natural protein
(albumins).
Fig. 5.70
Membranous Egg - Osmosis
FLUID MOVEMENT ACROSS
THE CAPILLARY
Fig. A
Capillaries are the sites of vascular
and interstitial fluid exchange
Fig. B
Which Figure shows
effects of hypertonic
and which shows
hypotonic solutions?
Fig. 5.69
Which line represents the change in
weight of the membranous egg?
Forces of Fluid Movement
•
Two driving forces for movement of
water between the blood plasma and
interstitial fluid are:
– hydrostatic pressure (blood pressure) and
– osmosis.
Forces of Fluid Movement
• Hydrostatic Pressure
– Hydrostatic pressure influences fluid
movement from the capillary into the
interstices and fluid movement from the
interstices into the capillary.
• Osmotic pressure
– Osmotic pressure influences fluid movement
from the capillary into the interstices and fluid
movement from the interstices into the
capillary.
16
Fluid Movement at the Arterial End
of Capillary
• Fluid movement across a capillary is due to
filtration pressure.
– Net filtration pressure is determined by subtracting
the net osmotic pressure from the net hydrostatic
pressure.
– Net filtration pressures differ between the arterial and
venous ends of a capillary. The difference results in
fluid movement from the arterial end (due to
hydrostatic pressure) and into the venous end (due to
osmotic gradients).
Hydrostatic Pressure at
Arterial End of Capillary
• There are two sources of
hydrostatic pressures that
influencing water
MOVEMENT at the
arterial end of the
capillary:
– capillary hydrostatic
pressure (or capillary blood
pressure) and
– interstitial fluid hydrostatic
pressure.
Fig. 5.88
Hydrostatic Pressure at
Arterial End of Capillary
There are two sources of hydrostatic pressures that
influencing water MOVEMENT at the arterial end of the
capillary:
capillary hydrostatic pressure (or capillary blood
pressure) and
interstitial fluid hydrostatic pressure.
Osmotic Pressure at
Arterial End of Capillary
• There are two sources of
osmotic pressures that
influencing water
MOVEMENT at the
arterial end of the
capillary:
• capillary osmotic
pressure (blood colloidal
pressure) and
• interstitial fluid osmotic
pressure.
Fig. 5.89
Net Driving Pressure
Arterial End of Capillary
•
Thus, to determine the
net driving force (filtration
pressure) at the arterial end of
the capillary both the net
hydrostatic pressure and the
net osmotic pressure must be
considered. The net filtration
pressure (NFP) of the capillary
is determined by subtracting
the net osmotic pressure
(NOP) from the net hydrostatic
pressure (NHP). NFP = NHP
(35 mm Hg. minus NOP (25
mm Hg.) = 10 mm Hg.
Fluid Movement at the Venous
End of Capillary
There are two sources of hydrostatic pressures that
influencing water MOVEMENT at the venous end of
the capillary: capillary hydrostatic pressure (or capillary
blood pressure) and interstitial fluid hydrostatic
pressure.
Fig. 5.90
17
Hydrostatic Pressure at
Venous End of Capillary
• There are two sources of
hydrostatic pressures that
influencing water
MOVEMENT at the
venous end of the
capillary:
– capillary hydrostatic
pressure (or capillary blood
pressure) and
– interstitial fluid hydrostatic
pressure.
Fig. 5.91
Osmotic Pressure at
Venous End of Capillary
• There are two sources of
osmotic pressures that
influencing water
movement at the venous
end of the capillary:
capillary osmotic
pressure (blood colloidal
pressure) and interstitial
fluid osmotic pressure.
Fig. 5.93
Net Driving Pressure at
Venous End of Capillary
•
Thus, to determine the net
driving force (filtration
pressure) at the venous end of
the capillary both the net
hydrostatic pressure and the
net osmotic pressure must be
considered. The net filtration
pressure (NFP) of the capillary
is determined by subtracting
the net osmotic pressure
(NOP) from the net hydrostatic
pressure (NHP). NFP = NHP
(17 mm Hg. minus NOP (25
mm Hg.) = -8 mm Hg.
Net Fluid Movement at Capillary
Fig. 5.94
• Fluid movements between the capillary and the
interstices are driven by the differences in the net
filtration pressures at the arterial and venous
ends of the capillary.
Summary of Driving Forces
• Summary of the driving
forces for fluid movement
between the capillary and
the interstices. Most of
the fluid is osmotically
returned into the venous
end of the capillary. Fluid
that does not return into
the capillary is returned to
venous circulation by way
of the lymphatic system.
ACTIVE PROCESSES
ACROSS THE PLASMA
MEMBRANE
Active transport moves solutes across
the plasma membrane with the
utilization of cellular energy (ATP).
Fig. 5.95
18
Active Transport
Two active processes for transport across the cell
membrane are active transport and vesicular transport.
• Active transport requires carrier proteins to provide the
mechanism of solute movement across the plasma
membrane.
• Vesicular transport requires that the substances be
moved across the plasma membrane in membranous
pouches (sacs) called vesicles. Two types of vesicular
transport are endocytosis and exocytosis.
– Endocytosis is the movement of substances into the cell, and
– Exocytosis is the movement of substances out of the cell.
Membrane Potentials
Passive processes such
as diffusion, osmosis, and
dialysis are processes of
equalization and do not
require the utilization of
cellular energy (ATP).
Processes of equalization
eliminate concentration
gradients.
Fig. 5.96
– For example, the electrical
potential of excitable
tissues would be eliminated
by the diffusion and
equalization of electrolytes
such as Na+ and K+
resulting in the inability of
cells to generate and
conduct electrical signals
• Active transport moves solutes across the
plasma membrane with the utilization of cellular
energy (ATP).
– Active transport requires plasma membrane carrier
proteins that function as solute pumps. Solute
pumps are commonly used for the movement of
solutes such as ionic sodium, potassium, and
calcium. Solute pumps typically transport their
specific solutes from an area of low concentration
to an area of high concentration, thus, against a
diffusion gradient.
Membrane Potentials
• Excitable cells such as
neurons and muscles,
utilize energy (ATP) to
actively maintain
electrical potentials by
membrane solute pumps.
To maintain electrical
potentials, solute pumps
actively transport and
maintain unequal
electrolyte
concentrations.
Fig. 5.97
Membrane Potentials
• An action potential of a
neuron is produced by
the movement of Na+
and K+ ions along the
portion of the neuron
called the axon. The
resting membrane
potential is reestablished
for the potential energy
needed for a sequential
action potential. Sodiumpotassium pumps actively
maintain the membrane
potential; Na+ in a high
concentration outside of
the cell and K+ in high
concentration inside the
cell.
Active Transport
Membrane Potentials
• An electrocardiogram
shows the electrical
activity of the heart.
Active transport
pumps maintain the
electrolyte gradients
needed to produce
the electrical
potentials.
Fig. 5.99
Fig. 5.98
19
Lab Activity 11Active Transport in Yeast
• Dead (boiled) yeast are
stained red because they
do not have the active
transport mechanisms
that prevent the entrance
of the dye, Congo Red,
into the cell. Living yeast
cells have active
transport mechanisms;
thus, are not stained red.
Fig. 5.100
VESICULAR TRANSPORT
• Vesicular transport
requires that
substances be moved
either into or out of
the cell in
membranous
pouches (sacs) called
vesicles. Two types of
vesicular transport
are exocytosis and
endocytosis.
Fig. 5.101
Fig. 5.102
Secretion
• Secretion is the release
of substances from a cell
(or may be defined as a
gland’s product).
Secretion of a substance
may occur by exocytosis
or by movement through
plasma membrane
proteins that function as
channels or pumps.
Fig. 5.102
– Secretory products
released by exocytosis
include hormones, mucus,
milk, enzymes, etc.
ENDOCYTOSIS
•
Endocytosis is a process where
substances are incorporation into the cell
by of the substances being entrapped in
membranous vesicles formed from the
plasma membrane.
– Endocytosis includes phagocytosis,
pinocytosis and receptor mediated
endocytosis.
Excretion
• Excretion is not a type of
vesicular transport.
Excretion is mentioned
here to avoid confusion
with secretion. Excretion
is the release of
modified and isolated
waste matter (such as
urine and sweat) from
the body.
– Excretory products such as
urine contain some
secretory products that are
considered as not useful to
the body.
Fig. 5.103
Phagocytosis
• Phagocytosis is the
process of engulfing
solid materials such as
bacteria or foreign bodies
by a phagocytic cell.
• Phagocytosis involves the
formation of plasma
membrane extensions
called pseudopods that
surround and engulf the
solid material into a
membranous vesicle
called a phagosome. The
phagosome fuses with
Fig. 5.104
organelles called
lysosomes, which
contribute digestive
enzymes for digestion of
the material.
20
Phagocytes
•
•
Phagocytes in the body
include macrophages and
other types of white blood cells
that help dispose of bacteria
and other foreign or damaged
substances.
Most phagocytes move by a
flowing of their protoplasm into
forming pseudopodia, a
movement called amoeboid
motion. Macrophages freely
roam the tissues of the body in
search of potential pathogenic
materials.
Fig. 4.13
Lab Activity 12 –
Macrophages of liver, Kupffer's cells
• Kupffer's cells are
identified on this slide
preparation by the
presence of
phagocytized carbon
particles (particles
were injected into
blood).
Fig. 5.105
Fig. 5.106
•
Lab Activity 13 –
Amoeba - amoeboid movement
and phagocytosis.
Amoebas are unicellular
organisms commonly
found in freshwater ponds
and streams. Observe for
the formation of cell
extensions called
pseudopods.
• Pseudopods allow for the
amoeba’s slow
movement and for the
phagocytosis of food
organisms.
• Observe the amoebas for
phagocytosis of Euglena
Fig. 5.108
• Paramecium showing
food vacuoles
(phagosomes) containing
Congo Red stained yeast
(100x). Lysosomes fuse
with food vacuoles and
release powerful
hydrolytic enzymes. The
hydrolytic enzymes result
in a change of the color of
the yeast to blue.
Fig. 5.110
PINOCYTOSIS
• Pinocytosis (bulk-phase
endocytosis) is the
engulfment of
extracellular fluids.
• This type of endocytosis
is nonspecific and occurs
by the invagination of the
plasma membrane to
form a membranous
vesicle.
Lab Activity 14 –
Paramecia and phagocytosis.
Fig. 5.111
RECEPTOR-MEDIATED
ENDOCYTOSIS
• Receptor-mediated
endocytosis specifically
engulfs substances
according to the
specificity of the
receptors. Membrane
receptors become
concentrated in an area
called a coated pit and
bind only to their receptor
specific molecule.
• Common receptors
include insulin and lowdensity lipoprotein (LDL)
receptors.
Fig. 5.112
21