Download Respiration: Aerobic Respiration

Respiration:!
Relationships Between Organ Systems"
food, water intake
oxygen intake
Starr and Taggart, Chapter 40!
DIGESTIVE"
SYSTEM
nutrients,
water,
salts
To the extent that you need it to
understand laboratory exercises or
lecture material, you are also
responsible for !
!
!
Chapter 37, Muscles and Skeleton!
Chapter 38, Circulation!
elimination
of carbon
dioxide
RESPIRATORY"
SYSTEM
oxygen
carbon
dioxide
CIRCULATORY"
SYSTEM
EXCRETORY"
SYSTEM
water
solutes
elimination
of food
residues
rapid transport
to and from all
living cells
elimination of
excess water,
salts, wastes
Figure 0.2
Page
Aerobic Respiration!
Atmospheric pressure"
!
•! The physiological process by which oxygen moves into internal
environment and carbon dioxide moves out!
–! Requires oxygen (O2) and produces carbon dioxide (CO2)!
–! Gases simply diffuse across cell membranes!
–! Driven by differing pressure gradients of gases on either side of the
cell membrane!
•! Primary determinant of differential pressure is the concentration of
gases in the atmosphere!
–! Oxygen = 21% of molecules in air; partial pressure = 0.21!
–! CO2 = 0.04% of molecules in air; partial pressure = 0.0004!
is the pressure exerted by the weight of the air
on objects on earth’s surface. !
At sea level, this is about 760 mm Hg. !
760 mm Hg
Nitrogen is 79% of air; its partial pressure is about
600 mm Hg!
Oxygen is 21% of air; its partial pressure is about
160 mm Hg.!
Other gases make up the remaining 1%, with
carbon dioxide exerting a partial pressure of
0.0004.!
Respiration by Diffusion!
Exchange of Gases Across Cell Membranes!
Basis for Diffusion!
Conditions for Diffusion!
•! Cellular metabolism!
–! uses O2 !
–! produces CO2 !
•! Therefore !
–! O2 concentrations inside
cells tend to be low!
–! CO2 concentrations inside
cells tend to be high!
•! Under the right conditions!
–! O2 will diffuse into cells
and CO2 will diffuse out of
cells!
•! Cell surfaces must be moist!
–! Gases only diffuse across cell
membranes in solution!
•! The membrane must be thin for
efficient diffusion!
•! O2 and CO2 concentrations must
differ across the membrane!
Amoeba!
•! Diffusion is adequate in single-celled
organisms!
–! concentrations of CO2 and O2 will
differ inside and outside of cell!
•! As animal size increases, surface-tovolume ratio decreases!
–! Size of cell is limited by need for
providing O2 to all parts of the cell!
–! Irregular shape provides only a
limited ability to increase size!
•! Multicellular animals!
–! Small, flattened animals can use the
body surface as their respiratory
surface!
–! Larger animals must have special
structures to increase respiratory
surface!
•! gills or lungs!
Planaria!
Counter-current blood flow"
Evolution of Respiratory Systems!
Aplysia: phylum Mollusca!
•! Respiratory structures exist!
–! Above flatworms!
•! Transport proteins!
–! Hemoglobin is most common!
•! Aquatic animals !
–! Dissolved O2 from H2O!
–! Gills !
•! Highly convoluted !
•! Thin cell membranes!
•! Blood flow can optimize
gas exchange across gills
by counter-current flow!
•! Fish can pick up 90% of
the O2 in water.!
water!
gills!
water!
Adaptation to Terrestrial Life: Insects!
Terrestrial Respiratory Systems!
•! Terrestrial animals take O2 from the air!
•! Moist cell surfaces are problematic in air!
•! Several ways to maintain moisture !
–! Spiracles!
–! Lungs!
•! All bring the respiratory system into the body!
•! In many organisms!
–! Transport proteins carry O2 in blood!
•!
•!
•!
•!
•!
Tracheal tubes open to outside, branch throughout body
Internal ends are filled with fluid to allow gas exchange.
Internalization of gas exchange conserves moisture.
There is no transport protein for oxygen in most insects.
Movement of O2 from trachea to cells is by diffusion, as always.!
branching
of trachea
trachea
(internal tube)
spiracle (opening
at body surface)
Insect tracheal system"
Adaptation to Terrestrial Life: Amphibians!
Vertebrate lungs
Complexity of branching increase with animals’ size.
AMPHIBIAN"
(salamander;
still rather like
fishes, early
amphibians)
AMPHIBIAN"
(frog; adults are
Adapted to dry
habitats)
MAMMAL"
(human;
adapted to
dry habitats)
REPTILE"
(lizard;
adapted
to dry
habitats)
nostril
glottis lung
•! Aquatic as juveniles !
•! More or less terrestrial as adults!
•! Respiratory systems are also
hybrid!
–! Juveniles have gills!
–! Adults have lungs!
•! Many species depend on skin for
a large part of their respiration!
–! In those species, skin must
remain moist for gas exchange
to occur!
•! Air is forced into the lungs by
movement of the bottom of the
oral cavity.!
Avian Lungs!
Mammalian Respiratory Tract!
•! Relatively inelastic!
•! Highly vascularized.!
•! Air moves though trachea into
trachea!
lungs, beyond lungs into air sacs.!
air sacs!
•! O2 is taken up as air goes through
lungs and moves into accessory
lung!
air sacs beyond lungs.!
•! Accessory air sac expand on
inhalation, contract on exhalation, Air sacs!
forcing air out and back into
lungs.!
•! More O2 is taken up as air goes
through lungs during exhalation.!
•! Complicated pathway with
multiple functions!
–! Nose -- also a sensory organ!
–! Pharynx -- shares transport of
ORAL CAVITY"
(MOUTH)!
food in part of its length!
–! Larynx or voice box: used for
speech!
–! Trachea or windpipe!
–! Bronchi: bifurcation of the
trachea!
PLEURAL "
MEMBRANE!
–! Bronchioli or bronchioles -INTERCOSTAL"
branch more and more finely
MUSCLE"
until they end in alveoli!
–! Alveoli -- next slide!
NASAL CAVITY"
PHARYNX (THROAT)"
!
EPIGLOTTIS
LARYNX (VOICE BOX)
!
TRACHEA (WINDPIPE)
LUNG"
BRONCHIAL TREE
!
DIAPHRAGM
!
Transport of Gases Through Body!
•! Most O2 is carried in blood by being
bound to hemoglobin in red blood
cells!
•! Hemoglobin!
alveolar sac
(sectioned)
alveolar sac
bronchiole
alveolar duct
alveoli
pulmonary
capillary
Once O2 is in the bloodstream, it must get
to tissues!
O2 is not sufficiently soluble in plasma to
satisfy mammalian needs for O2 !
Transport proteins carry O2 to cells!
Requires a molecule that can !
Pick up O2 from the lung!
Release O2 to the cells!
–! Consists of 4 peptides, each
containing a heme group, with
iron at its center.!
–! Has a great affinity for oxygen
when it is at high partial
pressure (in pulmonary
capillaries)!
–! Has a lower affinity for oxygen
in tissues, where partial pressure
is low!
Hemoglobin (Hb) and its Adaptations!
•! Fetal hemoglobin !
–! Higher O2 affinity than adult Hb!
•! Different amino acid sequence !
–! Picks up O2 from maternal blood!
•! Species adapt to high altitudes !
–! Hb with higher affinity for O2!
•! Individuals living at high altitudes !
–! increase their # of red blood cells!
–! Increase heart and lung size!
•! Altitude sickness!
–! Headache, nausea, irritability occur.!
–! Death can occur quite quickly.!
–! The best action is to get to a lower
altitude fast!!
•! Transporting O2 depends on weak binding of O2 to
hemoglobin (Hb)!
•! Molecules that bind strongly to Hb make it unavailable for
transport of O2.!
–! CO [carbon monoxide]!
–! Nitrates and nitrites!
•! As little as 20% carboxyhemoglobin can cause death!
•! Babies are most at risk from nitrates because fetal Hb has a
higher affinity for nitrates than adult HB!
Transport of CO2 !
•! CO2 must be removed from cells, and from the body.!
•! It differs from O2 in being more soluble in plasma. !
CO2 + H2O
+ carbonic anhydrase
H2CO3
carbonic acid
Poisoning O2 Transport!
– H+
HCO3+
bicarbonate
•! CO2 forms bicarbonate, which is highly soluble in plasma
•! Most carbon dioxide in blood is transported as bicarbonate
•! Some binds to hemoglobin
•! Small amount dissolves in blood
Control of Breathing!
•! Medulla oblongata sets main rhythm; centers in pons fine-tune it.!
•! Magnitude of breathing depends on concentration of oxygen and
H+.!
•! Brain detects H+, increases breathing.!
•! Carotid bodies and aortic bodies detect drop in oxygen, increase
breathing.!
–! Chemoreceptors that detect O2 concentration.!
Damaging Lungs!
Small particles ( < 0.5 µm) damage lungs!
!
Emphysema results from!
!
!asbestos, soot, coal, cotton, molds, etc!
Smoke also contains carcinogen!
!
10% of people who smoke for 20 ‘pack years’ develop lung cancer. !
Smoke or nicotine also lead to!
!
heart disease, macular degeneration.!
Oxygen Can Be Toxic!
O2 + e- ----> O2- "
–! Free radical, reacts with any molecule it contacts!
–! Can damage DNA, causing mutations!
•! Coping with O2- toxicity requires protective enzymes!
–!
–!
–!
–!
–!
Superoxide dismutase combines hydrogen ions [ H+] with O2- !
forms H2O2 (= hydrogen peroxide)!
Catalase breaks down H2O2 into water and O2!
These enzymes often require vitamins and/or anti-oxidants to function!
Failure to avoid O2 toxicity contributes to aging!
•! This is the reason foods that contain antioxidants are so popular as
“nutraceuticals”."
–! red wine"
–! pomegranates"
Fig. 41.17, p. 720
Genetics, Oxygen and Aging!
•!
Fast metabolism is correlated with short life spans!
–! Presumably because free radicals are generated!
–! Small mammals !
•!
•!
•!
High metabolism!
Food reduction increases life span!
Environmental factors affect lifespan"
–! Queen bees live much longer than workers!
•!
Genes for longevity exist !
–! Identified in C. elegans, Drosophila!
–! Extend lifespan !
•!
•!
by 5x in C. elegans!
by 50% in D. melanogaster!