Aerobic and Anaerobic Respiration

• Respiration is the exchange of oxygen (O2) and carbon dioxide (CO2).
• Oxygen deprivation can be fatal.
• Animals need a constant supply of O2 for metabolic processes to produce energy in ATP form.

Anaerobic vs Aerobic Respiration

• Anaerobic respiration: C6H12O6 becomes 2CH3COCOOH+4H
• 2CH3CHOHCOOH+4ATP also occurs during anaerobic respiation
• Aerobic respiration results in the production of 34 ATP
• Aerobic "respiratory gases" need to be produced on a continual basis
• Respiratory gases cannot be stored in the body
• Aerobic respiration: C6H12O6+6O2 becomes 6CO2+6H20+34ATP
• Vital physiological processes require ATP
• Processes that produce ATP require oxygen

External Respiration

• External respiration involves the transportation of O2 into and CO2 out of the body.
• External respiration occurs between the body and external environment

Internal Respiration

• Internal respiration transports O2 into and CO2 out of cells.
• Internal respiration occurs between the body and internal environment

Cellular Respiration

• Cellular respiration consists of intracellular catabolic reactions that convert stored energy to ATP.
• Oxygen is used during oxidative phosphorylation.

External Gas Exchange Membrane

• Gas exchange occurs across a thin respiratory membrane with one or two simple epithelia layers.
• The gas exchange membrane separates internal tissues from the environmental medium (air or water).
• External respiration involves environmental O2 -> membrane -> tissues.
• Dissolved CO2 processes are reversed with dissolved CO2 à membrane à environment
• Diffusion is a physiological process of movement that follows the laws of physics & chemistry.

Physics of Diffusion

• Fick's Law involves the transport of masses/solutes

• Diffusion Rate variables involved in Fick's Law include:

  • Diffusion coefficient (D)
  • Diffusion area (A)
  • Concentration difference (C1 - C2)
  • Distance (X)

• C1 & C2 = Regions of high and low concentrations of solutes

• A = Diffusion Area

• X = Distance separating the concentration regions

• D = Diffusion co-efficient, influenced by Physico-chemical properties of the solute & temperature

• J = D * A * (C1-C2)/X

Application of Fick's Law to the Diffusion of Respiratory Gases

• Gases do not always go from high to low concentration [] gradient
• Diffusion Rate (J) = D * A * (P1-P2) / X
• P1 & P2 = Regions of high and low partial pressure, respectively
• A = Diffusion Area
• X = Distance separating the concentration regions
• D = Diffusion co-efficient, influenced by Physico-chemical properties of the gas & temperature
• For large vertebrates, diffusion is an extremely slow process

Animals using O2 alone for diffusion

• Vertebrate muscle requires O2 partial pressure of ~ 40 mmHg
• Atmospheric O2 partial pressure = 160 mmHg
• The distance inside the tissue where O2 partial pressure reaches a minimum of 40 mmHg is ~ 1mm
• Diffusion alone is sufficient only for very small animals such as rotifers

Organism Size and Surface Area

• Oxygen requirement increases with mass
• As organisms get larger, a diffusion alone is not efficient
• Diffusion distance increases as mass increases
• The surface area gets proportionately smaller with mass
• Bacterium: Length: 1 µm, SA (m²): 6 x 10-12, Vol. (m³): 10-18, S/A:Vol: 6,000,000:1
• Amoeba: Length: 100 µm, SA (m²): 6 x 10-8, Vol. (m³): 10-12, S/A:Vol: 60,000:1
• Fly: Length: 10 mm, SA (m²): 6 x 10-4, Vol. (m³): 10-6, S/A:Vol: 600:1
• Dog: Length: 1 m, SA (m²): 6 x 10 to the power of 0, Vol. (m³): 10 to the power of 0, S/A:Vol: 6:1
• Whale: Length: 100 m, SA (m²): 6 x 10 to the power of 4, Vol. (m³): 10 to the power of 6, S/A:Vol: 0.06:1
• Surface area to volume ratio decreases with mass
• Respiratory organs with larger surface area and shorter diffusion distance is needed as organisms get larger

Counteracting Limited Respiration

• Animals prevent respiration from being diffusion limited via directly proportional relationships between the area (cm²) and body weight (g)
  • Mammals
  • Birds
  • Reptiles other than birds
  • Amphibians
  • Fish
• The thickness of the gas-exchange membrane may also effect efficiency

Respiration Steps in Larger Animals

• Most vertebrates gas-transfer system involves multiple steps:
  • Breathing movements (Ventilation)
  • Diffusion of gases across the respiratory epithelia
  • Circulatory system (Bulk transport of gases) - (Perfusion)
  • Diffusion of gases across capillary walls

Influence over Gas Exchange Systems

• The structure of the gas-exchange system in animals is highly influenced by:
  • Properties of the medium such as air vs. water
  • The requirements of animals

Physical Properties of Gases

• Dalton’s Law states that the total pressure exerted by a gas mixture (e.g., atmosphere) is the sum of individual pressures exerted by each gas in the mixture.
• Partial pressure (Pg) is the individual pressure of a gas in a mixture.
• The rate of gas diffusion is proportional to its partial pressure within the total gas mixture.
• O2 and CO2 flow based on their pressure gradient from high to low.

Air as a Respiratory Medium

• Air's composition and partial pressures in atmospheric air include:
  • 79% N2: Partial pressure of N2 = 600 mm Hg and PN2 = 760 mm Hg x 0.79 = 600 mm Hg
  • 21% O2: Partial pressure of O2= 160 mm Hg and PO2 = 760 mm Hg x 0.21 = 160 mm Hg
• At sea level, the total atmospheric pressure is 1 atm = 760 mm Hg
• High altitude reduces the inspired pressure of oxygen, but not the % of oxygen in the atmosphere:
  • La Rinconada, Peru has a population of 30,000 at 5100m
  • Bar Headed Geese can fly at >8000m altitude

Physical Properties of Air vs Water

• Air (20°C) vs Water (20°C) for physical properties and their effects on the respiratory gases:
  • Oxygen diffusion coefficient (m²/sec × 10-9): 20,300 vs 2.1 and Ratio (water/air) ~1:10,000
  • Carbon dioxide diffusion coefficient (m²/sec × 10-9): 16,000 vs 1.8 and Ratio (water/air) ~1:10,000
  • Oxygen solubility (ml/l): 1000 vs 33.1 and Ratio (water/air) 1:30
  • Carbon dioxide solubility (ml/l): 1000 vs 930 and Ratio (water/air) ~1
  • Oxygen concentration (mM) (at 1 atm): 8.7 vs .3 and Ratio (water/air) 1:30
  • Carbon dioxide concentration mM (at 1 atm): .01 vs .01 and Ratio (water/air) ~1
  • Density (kg/m³): 1.2 vs 998 and Ratio (water/air) ~800:1
  • Viscosity (poise × 10-2): .02 vs 1 and Ratio (water/air) 50:1
• Water is more viscous and dense causing a limited O2 environment

Oxygen Levels in Water

• Temperature also alters the dissolved O2 level in water
• There is a decreasing solubility of molecular oxygen in typical respiratory media as a function of temperature as temperature increases

Summary

• Respiratory gas exchange occurs through diffusion
• Respiratory gas exchange occurs following the difference of their partial pressure between the environment and animal’s body
• Larger animals face diffusion limitation, need specialized gas-exchange membrane, larger area and lower thickness
• Oxygen is less soluble in water, its solubility decreases with increasing temperature; thus, requiring respiratory adaptations for water breathing animals

Respiration Methods by Animal Type

• Respiration in water breathing (Fish)
• Respiration in air breathing animals (Insects & Birds)

Breathing Energetics

• Water-breathing is energetically more expensive than air breathing, because:
  • Less O2 is in water, causing it to be a larger medium
  • Air is less dense than water

Water Breathers

• Gills are invaginations of the body
  • Respiratory surfaces
  • Branched and folded
  • Increase diffusion area
• Ventilation/Water moves over the gills via the body:
  • Beating of cilia
  • Contractions of body muscles, create water current for gill ventilation

Types of Gills

• External gills are outside of the body
  • They extend out from the body, and do not have protective coverings
  • They also have extended outside body
• Internal gills are located within the body
  • Protected by chambers of the body
  • Currents of water is directed over the gills
  • Body protects gills

Gas Exchange Methods in Fish

• A double pumping mechanism occurs in bony and cartilaginous fish that involves:
  • Buccal cavity with pressure
  • Raises volume and the opercular cavity
• RAM ventilation occurs in pelagic fish such as some sharks and mackerel
  • These fish always swim with their mouth open because of no the double pump mechanism
  • Mackerel cannot fully oxygenate blood if prevented from active swimming leading to no ventilation

Fish Gills

• Four pairs of gill arches is the standard in fish
  • These are have blood capillaries, creating a secondary lammalae
  • Allows for gas exchange to occur
• Countercurrent flow is seen here where blood leaving the capillaries has the same O2 content as fully oxygenated water entering the gills
  • There are also some projections consisting of gill filaments, creating a primary lammalae

Countercurrent Gas Exchange

• During Concurrent Flow:
  • O2 + blood flows in the same direction
  • A H20 moves through the gill
  • Reaches equilibrium too soon resulting in an no gradient for diffusion and O2 absorption
• Countercurrent Flow:
  • Occurs in the opposite direction such the equilibrium isn't met
  • Diffusion can occur due to conc. gradient

Countercurrent Gas Exchangers

• Countercurrent gas exchangers efficient to increase PaO2, results in higher than PeO2 in the gill
• The P1-P2 is constant along the length of secondary lamella pressure gradient
• Unique systems create highly efficient O2 extractors for O2 poor mediums

Gill Structure in Killifish

• With temperatures that increase in water:
  • There is an increased diffusion efficienty
  • There is less O2 and dense tissue in 2nd lamellae

Tracheal System in Insects

• The tracheal system is found in insects and a intricate network with the trachea acting as a windpipe
  • It is an Invagination of the outer epidermis branching repeatedly into tracheoles
  • A small number of body tissues are in contact with tracheoles in order to get O2 to the body.
• Air enters and leaves through spiracles (openings on each side of exoskeleton)
• O2 > ECF > Cells
• CO2 > ECF > Tracheoles

Gas Transport in Insects

• The length of tissue diffusion path limit the size of the tissue via a not-efficient and very slow system
• Diffusion in tracheoles may work for small insects, larger use ventilation enough to maintain O2
• Ventilation:
  • Involves opening/closing spiracles and abdominal muscles
  • Needed by larger organisms
  • Directly supply O2 to body tissues and does not involving circulatory systems

Air Sacs and Lungs in Birds

• Birds do not inflate or deflate air
• These systems associated w/ lots of air sacs

Avian Lung

• 2 cycles:
• Ventillation occurs, during inhalation and exhalation
• blood flow also contributes here

Anatomy of Bird Lung

• Birds connect Anterior & posterior
• Oxygen levels are high
• Small amnt. of blood flow contact the external medium
• Gas exchange also has unidirectional pressure gradients

Transfer Systems in Birds

• These systems are found in Avian lungs
  • Blood flow farther down the tunes
  • Low amount of air compared to other options

High Altitude Adaptations

• Adaptations found in the Bird Lungs:
  • Have unidirectional air flow and cross surrent exchange
  • Larger Lungs with high capillarization

Mammalian Lung Characteristics

 - Blood Pool
 - Does not have an unidirectional flow
 - PP of 02 drops
 - has less than birds or fish

System Breakdown in Mammals

• Chamber which air is filtered:is Nsal
• Airway which sound occurs:Larsynx
• Air tube:Trachae
• Network to conduct gas exchange, where O2 goes into blood: Alveoilar walls

Alveoli Characteristics

• Alveoli are greater than blood capillary networks
• Surrounded by thin epithelial layers
• 1= Alveolus - where gas molecules accure

Other Lung Features

• Double layer: pleural sacs
• Protective for long and ribs: Thoracic

Vertebrae

• Same as daltons gas volume * pressure = volume * pressure

Pressure

• Internal : muscles contract
• External: muscles contract and move

Lung Volume

• End if normal inspiration to lungs

Volume Capacity Measurements

Total Lung Capacity (TLC) can be used to determine all lung capacities: - Volume, and Volume in air the lungs a single breath