Respirationfinal

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