Download GAS EXCHANGE:RESPIRATION

Gas Exchange
By Abby Dillard, Bailey Arrendale, and
Leslie Flanders
What is Gas
Exchange?
Gas Exchange is more commonly known as Respiration
Gas Exchange is the uptake of oxygen (O2) from the environment and discharge of
carbon dioxide (CO2) to the environment
Gas Exchange is necessary to support the production of ATP in cellular respiration
as well as to provide oxygen necessary for the process of cellular respiration
Both the Respiratory System and Circulatory System are involved in the process of
Gas Exchange
Where does the Oxygen
come from?
Respiratory Medium - source of Oxygen
Terrestrial animals acquire oxygen from air
Most of Earth’s Oxygen supply comes from the
atmosphere
Aquatic animals acquire oxygen from water
Oceans, lakes, rivers and other sources of water
contain Oxygen in a dissolved form
The volume of dissolved Oxygen present in water < the
volume of Oxygen in the air
How does the Oxygen and
Carbon Dioxide get
exchanged?
Respiratory Surface - the part of an animals body where gases are exchanged
Animals move Oxygen and Carbon Dioxide between the Respiratory
Surface and Environment through DIFFUSION (not active transport)
Rate of Diffusion is “proportional to the surface area across which
diffusion occurs and is inversely proportional to the square the distance
through which molecules must move (AP Edition Biology, 7th Edition,
Campbell/Reece)”
Significance: Respiratory surfaces are thin and have large surface
areas, an adaptation which helps to maximize gas exchange
Also, living cells must bathe in water to maintain their plasma
membrane. This means that the respiratory surface of animals
(terrestrial and aquatic) are moist - gas exchange takes place across
moist surfaces
More on the Respiratory
Surface...
The respiratory surface must be large enough to supply
an entire animal’s body with Oxygen as well as be large
enough to expel Carbon Dioxide from an animal’s entire
body
The structure of the respiratory surface is dependent
upon the size of the animal as well as whether the
animal is of terrestrial or aquatic life.
Respiratory surfaces are also influenced by the
organisms metabolic demand for gas exchange
There are specialized respiratory surfaces
Body Surface
The body surface of animals may be adapted for gas exchange
Gas Exchange occurs over the entire surface area of protists and other
unicellular organisms
For simple animals - like sponges or flatworms - gases are able to diffuse in
and out of the body because the plasma membrane of every cell in the animal
is close enough to the outside environment
For other animals - like frogs and earthworms - the entire outer layer of skin is
used as a respiratory organ. These types of animals always have to have
moist skin so the environments in which they can live in are limited.
A majority of animals are unable to perform Gas Exchange through their skin
or outside layer because there body lacks the mandatory body surface area
needed. Instead respiratory organs are folded or branched in these types of
animals to make up for lake of space
The three most common types of folded/branched respiratory organs are:
Gills, tracheae, and lungs
Gas Exchange
Gas Exchange occurs across
specialized respiratory surfaces
Gills in Aquatic Animals
Simple and distributed over
much of the body like a sea star
Gills in Aquatic Animals
Flaplike like in segmented
worms
Long and feathery and clustered
at the end of a head or tail like
scallops
Restricted to a local body region
like that of a crayfish
Total surface area of gills is often >
the rest of the animals body
Gills in Aquatic
Animals
The Process of Ventilation
Water enters the mouth of a fish ---- the water then passes through slits in the
pharynx ---- next the water flows over the gills ---- water exits the body
Fish use lots of energy obtaining O2 because water is dense and contains little
O2
Capillaries help to reduce the amount of energy a fish uses to obtain O2
and also makes the process more efficient
Blood flows through the capillaries in the direction opposite that water
flows through the gills. This process, known as countercurrent exchange,
makes the transfer of O2 to the blood very efficient
Countercurrent exchange is so efficient that gills can remove 80% of the
dissolved O2 in water as it passes over the respiratory surface
Disadvantages
Gills in Aquatic Animals
O2 concentrations in H2O are low - gills must be very effective to
compensate for this
Ventilation (increasing the flow of the respiratory medium over the
respiratory surface) helps makes gills more efficient. Without
ventilation, low O2 and high CO2 concentrations would form around
the gills as gases are exchanged
Advantages
Keeping plasma membranes of the respiratory surface moist is not a
problem
Tracheal Systems in Insects
Insects
Examples: Grasshopper
The tracheal system is a gas exchange system of branched, chitin-lined tubes
that infiltrate the body and carry O2 directly to cells in insects
Tracheal Systems in Insects
Insects
Composed of air tubes that branch throughout the body
The largest tube, called the tracheae, opens to the outside. The finest
branches extend to the surface of almost every cell - allowing for gas
exchange via diffusion
Tracheal Adaptation are related to bioenergetics
For a small insect, ventilation via the trachea brings in enough O2 and
put out enough CO2. Larger insects that have higher energy demands
use rhythmic body movements to compress and expand the air tubes
to properly ventilate there tracheal system
Tracheal Systems in Insects
Air as a respiratory medium
Disadvantages
Respiratory system must be moist and the air dries it out through
evaporation
Advantages
Air > concentration of O2 than water does
Respiratory systems do not have to be ventilated as often as gills do
because O2 and CO2 diffuse faster in air, terrestrial animals also use less
energy to obtain O2
Lungs
Terrestrial Animals
Examples: Spiders, Land Snails
Lungs are a respiratory surface of terrestrial vertebrates, snails, and spiders
that connects to the atmosphere by narrow tubes
Lungs
Lungs are located in one part of the body (unlike the tracheal system which is
branched throughout the body)
The animals metabolic rate dictates the size and complexity of the lungs endotherms exchange surface > ectotherms exchange surface
The respiratory surface of the lung is not directly linked to the other parts of the
body
To make up for this the lungs work closely with the circulatory system which
transports gases in and out of the body
The respiratory surface is composed of a net of capillaries under the
epithelium
Mammalian Respiratory
System
Located in the thoracic (chest cavity)
Lungs in mammals have a spongy texture and are honeycombed with a moist
epithelium that serves as the respiratory surface
Air reaches the lungs through a system of branching ducts
Mammalian Respiratory
System
Air enters through the nostrils. In the nostrils the air is filtered and warmed.
The nostril is also where odors are detected.
Air flows from the nostril to the nasal cavity
Mammalian Respiratory
System
Air travels from the nasal cavity into the pharynx, which is an intersection
where the passage ways of food and air go
If food is swallowed the larynx moves up with causes the epiglottis to cover
the glottis (opening of the windpipe). If food is not being swallowed the
More on the larynx...
glottis is open, which allows air to pass
- The wall of the larynx is
reinforced with cartilage
- It is the voice box - when air
travels into the larynx air goes
past vocal chords. Sounds are
produced when voluntary
muscles of the voice box are
tensed, which causes them to
vibrate and produces sound
Mammalian Respiratory
System
Air is then passed to the trachea, more commonly known as the windpipe.
The trachea is a portion of the respiratory system that has C-shaped rings.
The air that travels through the trachea is then passed to two bronchi. One
bronchus leads to the left lung and the other leads to the right lung
Mammalian Respiratory
System
From the bronchi, air travels to the bronchioles, which are fine branches of
the bronchi.
Note: Major components of the respiratory system are covered with cilia
and a layer of mucus. The mucus traps unwanted things (like dust) and the
cilia moves the mucus to the pharynx where it is then swallowed and sent
down the esophagus
Mammalian Respiratory
System
At the end of the bronchioles are clusters of air sacs called alveoli. The
alveoli is the location of gas exchange
The air that enters the alveoli dissolves in a moist films and diffuses across
the epithelium into capillaries that surround each alveolus. CO2 and O2 are
then diffused - they diffuse in different directions
Mammalian Respiratory
System
At the end of the bronchioles are clusters of air sacs called alveoli. The
alveoli is the location of gas exchange
The air that enters the alveoli dissolves in a moist films and diffuses across
the epithelium into capillaries that surround each alveolus. CO2 and O2 are
then diffused - they diffuse in different directions
Mammalian Respiratory
System
Video of the Respiratory System
http://www.youtube.com/watch?v=HiT621PrrO0
Gas Exchange
Breathing ventilates the lungs
Breathing
The process that ventilates the lungs is called breathing
Breathing is a process that involves alternate inhalation and exhalation of
air that ventilates the lungs
Breathing
Amphibians breathe ventilates it’s lungs through positive pressure
breathing
Positive pressure breathing is a breathing system in which air is forced
into the lungs
Muscles of the oral cavity lowers ---- air comes into the body via the
nostrils ---- once air is in the body the muscles of the oral cavity rise
(at this point the nostrils and mouth is shut) ---- air is then forced down
the trachea ---- air is forced out of the body when the lungs and
muscles of the body recoils
Breathing
Mammals breathe ventilates it’s lungs through negative pressure breathing
Negative pressure breathing is a breathing system in which air is
pulled into the lungs
Breathing
During ventilation the volume of the lungs change
Lung volume increase during inhalation as a result of the rib muscles
and diaphragm contracting. The diaphragm is a sheet of skeletal
muscles that forms the bottom of the chest cavity. The contraction of
the rib muscle causes the ribs to expand and move upward toward the
breastbone. The chest cavity also expands.
Air flows from an area of high pressure to low pressure. At this point
air pressure within the alveoli < atmospheric pressure so air is able to
travel into the respiratory system
During vigorous exercise, the body requires more air. As a result the
volume of the lungs increases further so that more air can be
exchanged in the body. The neck, back, and chest muscles help the
volume of the lungs to further increase by raising the rib cage even
higher. The volume of ventilation can also be increased through the
“visceral pump” - when visceral organs like the stomach and liver slide
Breathing
During ventilation the volume of the lungs change
Lung volume decrease during inhalation as a result of the rib muscles
and diaphragm relax, which causes the lung volume to be reduced
Air flows from an area of high pressure to low pressure. At this point
air pressure within the alveoli > atmospheric pressure so air is able to
travel out of the respiratory system
During rest, the volume of the lungs decreases further
Breathing
Tidal Volume
The volume of air an animal inhales and exhales with each breath
The average tidal volume of an animal at rest is 500mL. The maximum
amount of air an animal can inhale and exhale is called vital capacity.
Vital capacity is reached in females around 3.4L and in males around
4.8
The lungs are capable of holding more than the vital capacity,
however, the alveoli would have to completely collapse which is
impossible. As a result, a residual volume (amount of air that
remains in the lungs after forcefully exhaling) remains in the
lungs
Inhaled air is mixed with residual air because lungs do not
completely fill up and empty each time. The mixing of the two
types of air causes the O2 concentration in the alveoli to become
less than air in the atmosphere. This limits the gas exchange,
however the CO2 in the residual air is important for controlling
the breathing rate in animals and pH of blood
Bird’s Breathing
Ventilation in birds is much more complicated than in mammals
Birds have lungs like mammals as well as 8-9 air sacs
Air sacs are not part of gas exchange. Instead they keep air
flowing in the bird’s lungs
Birds do not have alveoli. Instead they have parabronchi, which
allow air to flow past the respiratory system in one direction
Bird’s Breathing
Bird’s ventilation systems flow in only ONE direction
Since bird’s ventilation flows in one direction, their O2 is completely
replenished
Maximum O2 concentration in birds > O2 concentration in
mammals
Because of this bird are able to function more efficiently at high
altitudes than mammals are
The Brain + Breathing
Breathing control centers are responsible for regulating breathing
Breathing control centers are located in the brain - the medulla
oblongata and the pons
The medulla oblongata establishes a breathing rhythm with the
help of the pons
Secondary control of breathing is controlled by sensors in the aorta
and carotid arteries
The sensors monitor O2 and CO2 concentrations in the blood as
well as pH in the blood
Negative feedback mechanism prevents the lungs from expanding too
much
Stretch sensors in the lung tissue send signals to the brain that
can stop the medulla oblongata’s control center
The Brain + Breathing
More on the medulla’s control center...
Controls breathing activity by monitoring changes of the pH of tissue
fluid (cerebrospinal fluid), which is the fluid that the brain is suspended
in
The pH of the cerebrospinal fluid is determined by CO2
concentration in the blood
CO2 diffuses from the blood to the cerebrospinal fluid where it
reacts with water to form carbonic acid
CO2 + H2O
H2CO3
When there is an increase in CO2 (and in turn a decrease in
pH levels in the cerebrospinal fluid) the medulla oblongata
increases the rate at which a mammal breathes. This allows
CO2 to exit the body quickly and the pH returns back to an
acceptable level
The Brain + Breathing
The concentration of O2 in the blood has little affect on breathing control
There are, however, O2 sensors in the aorta and carotid artery. If
levels of O2 get to low in the body then the sensors will send signals
to the breathing control center and the control center will increase the
rate of breathing and get the O2 levels back to normal
Cellular respiration involves O2 and CO2 so...
A rise in CO2 generally means a drop in O2 has occurred (and
vice versa). If this occurs the breathing control center will correct
the problem
Hyperventilation is taking deep and fast breaths. Hyperventilation
causes massive amounts of CO2 to leave the blood. The lack of
CO2 “tricks” the breathing control centers to stop temporarily and
send signals to the diaphragm and ribs. Breathing stops until the
CO2 rates return to normal, which causes the breathing control
center to come back on
The Brain + Breathing
Blood control centers are only effective when it works with the
cardiovascular system
This way ventilation in the lungs and the amount of blood flowing
through the alveolar capillaries are equivalent
Example: During exercise the heart has to work harder. This causes a
person breathing to increase which increase O2 intake and CO2
removal from the body as blood flows through the lungs
The Brain + Breathing
Gas Exchange
Respiratory Pigments Bind and
Transport Gases
Respiratory Pigments
The respiratory system is responsible for meeting the metabolic demands
of the entire body, which means that it is responsible for the uptake of large
amounts of O2 and large removals of CO2
Evolutions in the transport system have evolved to keep up with the
demands for the large quantities of O2 uptake and CO2 removal
required by the body
Process of evolution of types of animals are independent of one
another
Respiratory Pigments
Partial Pressure Gradients - A measure of the concentration of one gas in a
mixture of gas. It is the pressure exerted by a particular gas in a mixture of
gases. Example: the pressure exerted by O2 in air
Gas diffuses down pressure gradients in the lungs and other organs
The diffusion of gas is dependent upon differences in partial pressure
gradient. O2 and CO2 diffuse where their partial pressure is higher to
where it is lower
Respiratory Pigments
Respiratory Pigments
Respiratory Pigments - A protein that transports most oxygen in blood
Transport gases and help buffer blood
Increases the amount of O2 blood can hold
Many arthropods and molluscs have hemocyannin and vertebrates as
well as some invertebrates have hemoglobin
Respiratory Pigments
Oxygen Transport
Hemoglobin is a protein present in almost all vertebrates as well as
many invertebrates
Hemoglobin loading and unloading of O2
Respiratory Pigments
Oxygen Transport
Disassociation curve for
hemoglobin - A chart showing the
relative amounts of O2 bound to
hemoglobin when the pigment is
exposed to solutions varying in
their partial pressure of dissolves
O2, pH, or other characteristics
Respiratory Pigments
Oxygen Transport
A drop in pH lowers hemoglobins
affinity to O2, known as the Bohr
shift
CO2 and H20 react and form
carbonic acid. This facilitates the
release of more oxygen from
hemoglobin in the vicinity of active
tissues - more O2 can be used for
cellular respiration
Respiratory Pigments
Carbon Dioxide Transport
Hemoglobin helps with CO2 transport and helps to prevent dangerous
pH changes in blood.
7% of the CO2 from respiring cells is transported in a blood plasma
solution, 23% of CO2 binds to multiple amino groups of hemoglobin,
and 70% is transported in the blood in the form of bicarbonate ions
Respiratory Pigments
Carbon Dioxide Transport - CO2 diffuses into
blood plasma and then into erythrocytes
1. CO2 reacts with H20 with help from
an enzyme called carbonic anhydrase.
This forms H2CO3
H2CO3 dissociates into H+ and HCO3-.
H ions attach to hemoglobin and other
protein (helps to minimize pH change in
blood). HCO3- diffuses into plasma
Blood flows through the lungs and the
entire process is reversed - diffusion of
CO2 out of blood moves the chemical
equilibrium in favor to change HCO3- to
CO2
Respiratory Pigments
Many animals respiratory system require much more O2 than normal respiratory systems
and have evolved over time to meet the O2 demands there bodies require. Theses
changes result from natural selection
Long distance runners
Experimentation: Stan Lindstedt from the University of Wyoming and
University of Bern conducted an experiment with pronghorns to see how they
maintain speed and endurance. The results show that pronghorns use O2 3x
as much as an animals their size would normally consume.
Why? Pronghorns have a larger surface area for O2 in their lungs, they
maintain higher muscle temperature, have higher density and volume of
mitochondria ---- this results from evolution in physiological mechanisms
presents in other animals (from natural selection)
Mammals that dive under water for long periods of time
Weddell seals can store large amounts of O2 and deplete it at a slow pace
Why? Adaptations: Weddell seals use little muscles to swim, heart rate and O2
rate decrease during dives, blood supply to the muscles is regulated and at
times, cut off, Weddell seals have high amounts of myoglobin (O2 storing
protein)