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RESPIRATION
Respiration
Gas exchange- also called respiration Uptake of molecular oxygen from the environment
and the discharge of CO2
Respiration is not only exclusive to this concept; presence of cellular respiration Aerobic respiration Anaerobic respiration
Cellular respiration
Chemical breakdown of food to yield ATPIs a catabolic processAerobic Respiration- presence of a complete
redox process due to the presence of O2
More ATP yield
Anaerobic Respiration- absence of O2
Less ATP is produced
Glycolysis
Glycolysis- process of breaking down sugar to yield ATP
Both an aerobic and anaerobic processAnaerobic- less ATP is produced
Used by bacteria in producing energy; less efficient
Aerobic-more ATP is produced of more products that can be broken down through oxidative phosphorylation
Aerobic Respiration
Present in mitochondria
Anaerobic Respiration
Fermentation- a process that does not use oxygen to yield products
Two types Lactic Acid Fermentation Yeast Fermentation
Lactic Acid Fermentation
Present in muscles Too much lactic acid can cause cramps
Yeast Fermentation
Also called alcohol fermentationEthanol is a by-product of yeast fermentationSaccharomyces cerevisiae
Gas Exchange in Plants (Photosynthesis)
CO2 is taken in while O2 is releasedFactors such as temperature, wind, humidity
affect gas exchange in plantsDifferent plants employ different strategies in
acquiring CO2 from the environmentPresence of C3, C4 and CAM plants
C3, C4 and CAM
Different group of plants have different strategies in acquiring CO2 for photosynthesis
All pathways start from a single CO2 from the environment
C3 pathway
The most basic among the threeA basic 6-C compound is broken down into
two 3-C compound3-C is more stable than the 6-C compound
C4 pathway
C4 plants produce an intermediate 4-C compound before converting it to the 3-C
Special structure is present in producing the 4-C compound Bundle sheath
Employs spatial adaptation
CAM pathway
Crassulacean acid metabolic pathwayCommon in plants under the family
CrassulaceaeDifference to the C4 pathway is the used of
temporal adaptationCO2 is taken at night when the temperature is
low and the stomata are open
Animal Respiration
Respiration or gas exchange is necessary to support ATP production
May involve both respiratory system and circulatory system
Animal Respiration
Respiratory medium- oxygen source Air for terrestrial animals Water for aquatic animals
Oxygen in water is less concentrated compared to air Oxygen exists in a dissolved form Many factors affect oxygen concentration in water such
as temperature
Respiratory Surface
Respiratory Surface- part of an animal where gas exchange occurs
Gas exchange occurs entirely through diffusion
Diffusion rate- directly proportional to the SA where it occurs Inversely proportional to the square to which
molecules must move
Respiratory Surface
Therefore, respiratory surface have thin walls and have a large SA
Also, water is needed by all living cells to maintain its plasma membrane
Thus, respiratory surfaces are moist, dissolving first CO2 and O2 in water
Respiratory Surface
Respiratory surface structure: Depends on the size of the organism Depends on the organism’s habitat Depends on its metabolic demands
Endotherm has a larger SA of respiratory surface than a similar-sized ectotherm
Protists and Some Simple Animals
Gas exchange occurs at the entire length of unicellular organisms
Same for simple animals such as poriferans, cnidarians and flatworms
Cell in their body is close enough to the respiratory medium
More Complex Animals
Respiratory Surface- does not have direct access to the respiratory medium
Respiratory surface- thin, moist epithelium Separates the respiratory medium from blood and
capillaries
Cutaneous Respiration
Animals such as earthworms and amphibians use the entire length of their body to respire
Skin is the respiratory organShould always be moist, near bodies of water
and/or dampWhy?
Cutaneous Respiration
Animals that respire through the skin are usually small, long and thin, or flat
High SA to V ratio
The Most Common Respiratory Organs
If an animal lacks sufficient body SA for exchange of gases the solution is an extensively folded respiratory organ
Most common are tracheal system, gills and lungs
Gills: Respiratory adaptations of aquatic animals
Gills- outfolding of the body suspended in water
Can be internal or externalShape varies
Sea stars- gills have simple shape and distributed all over the body
Annelids- flaplike gills that extended from each segment or long feathery gills found on the head or tail
Clams, fish- gills are found in one local region
Gills
Total surface area is often larger than that of the body
Water as a respiratory medium
Advantage Cell membranes of respiratory surface are always
moist
Disadvantage Less concentration of O2
High temp, high salinity= low O2 conc
Ventilation
Process of increasing contact between the respiratory medium and respiratory surface
Solution to the low O2 conc in waterWithout ventilation a region of high O2 conc
and high CO2 conc can occur
Ventilation
Crayfish and lobster- use paddlelike appendages in driving water over the gills
Fish- gills are ventilated through the passage of water through the mouth and to the gills May require large amount of energy
Fish Ventilation
High volume of water is needed to ventilate the gills thereby increasing the energy used
Arrangement of gill capillaries decrease energy use
Blood moves opposite the direction of the water
The process is called countercurrent exchange
Countercurrent exchange
There exists a diffusion gradient that favors the movement of O2 from water to blood in the capillaries
Very efficient: can remove up to 80% of O2 dissolved in water
Is also important in temperature regulation and other physiological processes
Countercurrent exchange
Countercurrent exchange
Equilibrium is reached,Diffusion stops
Equilibrium is not reached, Diffusion constantly occuring
Terrestrial Respiratory Structures: Tracheal Systems and Lungs
Air as a respiratory medium High concentration of O2 Diffusion of O2 and CO2 is faster, ventilation is not
much needed Partial pressure of gases dictates the rapid transfer of
the two gases involve
Air as a respiratory medium
When ventilation is needed, less energy is needed to pump air Air is much lighter than water Less volume of air is needed to obtain equal amount of
O2 from H2O Disadvantage: Respiratory epithelium should always
be moist Solution: highly folded respiratory structure
Tracheal Systems
Tracheal Systems
Made up of air tubes that branch throughout the body; not folded
Largest tubes: called tracheae; open to the outside
Spiracles- outside openingTracheoles: finer branch of tracheae, directly
connected to cell surface
Tracheal System
Gas exchange is through diffusion across the moist epithelium at the terminal ends of the system
Circulatory system is not involvedDiffusion is enough to support cellular
respirationLarger insects with higher energy demands
ventilate through rhythmic body movements
Tracheal System
Flying insect has high metabolic demandWings act as bellows in pumping air through
the tracheal systemFlight muscle cells are packed with
mitochondria, tracheal tubes supply ample amount of O2
Lungs
Confined to one locationGap between respiratory medium and
transport tissue is bridged by the circulatory system
Have dense net of capillaries under the epithelium that forms the respiratory surface
Evolved in spiders, terrestrial snails, vertebrates
Lungs
Bronchiole
Lungs
Amphibians small lungs, rely mainly through skin
Reptiles, birds, mammals rely mainly on their lungs
Turtles: exception: supplement lung breathing through epithelial surface through the mouth and anus
Some fish have lungs: lungfishesSize and complexity of lungs: correlated to an
animal’s metabolic rate
African Lungfish
Mammalian Respiration
Mammalian Lung Structure: spongy, honeycombed with moist epithelium
Branching ducts convey air to lungsAir enters through the nostrilsFiltered by hairs and ciliaAir is warmed, humidified and sampled for
odors
Mammalian Respiration
Air moves from the nasal passage to the pharynx and then to the larynx
The act of swallowing moves the larynx upward tipping the epiglottis over the glottis
Glottis- opening of the windpipeLarynx- adapted as voiceboxSyrinx- vocal organ of birds
Found at the base of the trachea Produce sound without the vocal chords found in
mammals
Mammalian Respiration
Sound: produced when voluntary muscles stretch and vibrate during the process
High-pitched sound: tight, rapid vibrationLow-pitched sound: less tense, slow vibration
Mammalian Respiration
From the trachea: forks into two bronchiShaped like an inverted treeFiner branches are called bronchiolesEpithelial lining is covered with mucus and
beating ciliaMucus traps contaminant, while, the cilia
moves this to the pharynx where it can be swallowed
Mammalian Respiration
Bronchioles: dead-end into cluster of air sac called alveolus
Gas exchange occurs through the thin epithelium of alveoli
SA: 100 M2 in humans
Ventilating the Lungs
Terrestrial organisms also rely on ventilation Maintains high O2 and low CO2 at the gas exchange
surface
Process of ventilating the lungs is called breathing Breathing- alternate process of inhalation and
exhalation
Two types Positive pressure breathing Negative pressure breathing
Positive pressure breathing
Frogs ventilate their lungs through positive pressure breathing
In a breathing cycle: Muscles lower the oral cavity floor (becomes enlarge
and draws air through the nostrils) Closing of the mouth and nostril (oral cavity floor rises
and forces air into the trachea) Air is force out/exhaled (elastic recoil of lungs and
muscular contraction of chest)
Negative Pressure Breathing
Works like a suction pump (air is pulled rather than pushed)
Negative pressure is produced due to action of chest muscle Relaxation of chest muscle pushes air; contraction
pulls air in
Expansion of lungs is possible due to its double-walled sac Inner sac adheres to the lungs Outer sac adheres to the chest cavity walls Space in between is filled with fluid
Surface Tension
Surface tension- responsible for the behavior of the lungs
The lungs slide past each other but cannot be pulled separately
The surface tension couples the movement of the lungs to the movement of the rib cage
Breathing
Inhalation- Contraction of muscles (rib muscles and diaphragm) Increases volume of chest cavity Decreases alveolar air pressure Rib cage expands (ribs pulled upward; breastbone
pushed forward)
Gas moves from an area of higher partial pressure to low partial pressure
Air moves from the URT to alveoli of LRT
Breathing
Exhalation- relaxation of muscles Rib muscles and diaphragm relax Lung volume is reduced Inc in alveolar air pressure
Shallow breathing- rib muscle and diaphragm are responsible
Deep breathing- muscles of the back, neck and chest are responsible
Some animals employ visceral pump- adds to the piston like action of the diaphragm
Breathing
Tidal volume- volume of air inhaled and exhaled in each breath Ave human tidal volume is 500 ml
Vital capacity- max tidal volume during forced breathing 3.4 L female; 4.8 L male
Residual volume- air left in the lungs during exhalation Lungs hold more air than the vital capacity
Breathing
Age or disease decrease the elasticity of the lungs Residual volume increases at the expense of vital
capacity Max O2 conc in the alveoli decreases Gas exchange efficiency is decreased
Ventilation in birds
More complex than mammalsPresence of air sacsDo not function directly in gas exchange; acts
as bellowsLungs and air sacs- ventilated during
breathingPresence of parabronchi rather than alveoli
Air moves in one direction Air is completely exchanged Max O2 conc is higher in birds than in mammals
Regulation of Breathing
Breathing – controlled by the medulla oblonagata and the pons
This ensures that respiration is coordinated with circulation
Medulla oblongata- major control center of breathing
Control center in the pons works synergistic with the control center of the medulla oblongata
Regulation of Breathing
Negative feedback- helps maintain breathingStretch sensors- found in the lungs send
impulses to the medulla (inhibits the breathing control center)
Medulla- monitors CO2 level of the blood CO2 conc is detected through slight change in blood
and tissue fluid pH Carbonic acid lowers pH Drop in pH increases rate of rate and depth of
breathing
Oxygen Concentration
Oxygen Concentration- have little effect to breathing control center
Severe depression of O2 conc stimulates O2 sensors in the aorta and carotid arteries to send alarm signals
Breathing rate is increased by the control centers
Increase in CO2 conc is a good indicator of decrease in O2 conc
Hyperventilation
Excessive deep, rapid breathing inc CO2 conc in the blood
Breathing centers temporarily stops workingImpulses to the rib muscles and diaphragm
are inhibitedBreathing resumes when CO2 conc inc
Different Factors Affect Breathing
Nervous and chemical signals affects rate and depth of breathing
Most efficient if it works in tandem with the circulatory system
E.g. Exercise: inc cardiac output-inc breathing rate Enhances O2 uptake and CO2 removal
Respiratory pigments: transports gases and buffers the blood
Low solubility of O2- problem if O2 is transported via the circulatory system E.g. Normal human consume 2L of O2 per minute Only 4.5 ml of O2 can dissolve into a L of blood in the
lungs If 80% dissolved O2 would be delivered, 500 L of
blood should be pumped per minute (a ton per 2 mins) Unrealistic!!!! Special respiratory pigments are used
Respiratory Pigments
Transports O2 instead of dissolving into a solution
Inc O2 that can be carried in the blood (~200 mL O2 per L in mammalian blood)
Decreases cardiac output (20-25 L per min)
Respiratory Pigments
Binds O2 reversibly Loads O2 from respiratory organ; unloads in other
parts of the body
Hemocyanin- found in hemolymph of arthropods and many mollusks
Copper- acts as the oxygen-binding component
Hemoglobin- respiratory pigment of all vertebrates
Hemoglobin
Consists of four heme subunitsIron acts as the binding site of O2Loading and unloading of O2 depends on the
property of each subunits called cooperativityAffinity is dependent to the conformation of
each subunit Binding of one O2 molecule to one subunit induces the
inc in affinity of other subunits Unloading of one O2 molecule decreases the affinity of
other subunits
Dissociation Curves of Gases
Cooperativity of heme subunits is shown in a dissociation curve
Steep slope- slight change in Po2 causes substantial loading or unloading of O2
Because of cooperativity, slight drop in Po2
causes a relatively large inc in O2 to be unloaded
The Bohr Shift
A shift to the right of the oxygen hemoglobin dissociation curve
Brought about by increase CO2 or low blood pH
Decrease in affinity of hemoglobin to O2Greater efficiency of O2 unloading
Carbon Dioxide transport
Hemoglobin- also transports CO2 not only O2 Assists in buffering the blood
Blood released by respiring cells: 7%- transported in the solution of blood plasma 23% - bind to amino group of hemoglobin 70% - transported in the blood in the form of carbonic
acid
Carbon Dioxide Transport
CO2- converted in the red blood cells into bicarbonate Reacts first with water to form carbonic acid (carbonic
anhydrase) Dissociates into H+ and bicarbonate H ions- attach to different sites in the Hb and other
proteins Bicarbonate ions- diffuse into the plasma Movement of blood through the lungs reverses the
process favoring the conversion of bicarbonate to CO2
Deep-diving air breathers
Stockpile oxygen- O2 is reserved in the blood and muscles (e.g. Weddell seal)
High percentage of myoglobinDec heart rate and O2 consumption20-min dive- O2 in myoglobin is used up
Energy is erived from fermentation rather than respiration