[bio] Respiration

RESPIRATION

Respiration Gas exchange- also called respiration 

Uptake of molecular oxygen from the environment and the discharge of CO2

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Respiration is not only exclusive to this concept; presence of cellular respiration Aerobic respiration Anaerobic respiration

Cellular respiration Chemical breakdown of food to yield ATP Is a catabolic process Aerobic 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 process Anaerobic- 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 fermentation Ethanol is a by-product of yeast fermentation Saccharomyces cerevisiae

Gas Exchange in Plants (Photosynthesis) CO2 is taken in while O2 is released Factors such as temperature, wind, humidity affect

gas exchange in plants Different plants employ different strategies in acquiring CO2 from the environment Presence 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 three A basic 6-C compound is broken down into two 3-C

compound 3-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 pathway Common in plants under the family Crassulaceae Difference to the C4 pathway is the used of temporal

adaptation CO2 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 similarsized 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 organ Should always be moist, near bodies of water and/or damp Why?

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 external Shape varies 

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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 water Without 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  

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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

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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 opening Tracheoles: 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 involved Diffusion is enough to support cellular respiration Larger insects with higher energy demands ventilate through rhythmic body movements

Tracheal System Flying insect has high metabolic demand Wings act as bellows in pumping air through the

tracheal system Flight muscle cells are packed with mitochondria, tracheal tubes supply ample amount of O2

Lungs Confined to one location Gap 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: lungfishes Size 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 lungs Air enters through the nostrils Filtered by hairs and cilia Air 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 windpipe Larynx- adapted as voicebox Syrinx- 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 vibration Low-pitched sound: less tense, slow vibration

Mammalian Respiration From the trachea: forks into two bronchi Shaped like an inverted tree Finer branches are called bronchioles Epithelial lining is covered with mucus and beating

cilia Mucus 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: 

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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 mammals Presence of air sacs Do not function directly in gas exchange; acts as

bellows Lungs and air sacs- ventilated during breathing Presence 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 breathing Stretch sensors- found in the lungs send impulses to

the medulla (inhibits the breathing control center) Medulla- monitors CO2 level of the blood 

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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 working Impulses to the rib muscles and diaphragm are inhibited Breathing 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   

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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 subunits Iron acts as the binding site of O2 Loading and unloading of O2 depends on the

property of each subunits called cooperativity Affinity is dependent to the conformation of each subunit 

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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 O2 Greater 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 

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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 myoglobin Dec heart rate and O2 consumption 20-min dive- O2 in myoglobin is used up 

Energy is erived from fermentation rather than respiration