Respiration Flashcards
(48 cards)
Describe the great oxygenation event
- Little free O2 in the atmosphere, until the “Great Oxygenation Event”
- Cyanobacteria living in the oceans started producing oxygen through photosynthesis
- As oxygen built up in the atmosphere anaerobic bacteria were killed leading to Earth’s first mass extinction
Why is oxygen used in respiration
O2 is well suited to serve as an electron acceptor in the oxidation of carbon-based fuels.
- O2 is stable and consequently accumulated in the Earth’s atmosphere
- The reduction of O2 provides one of the largest free energy release per electron transfer (just less than fluorine)
- Aerobic metabolism yields at least 4-fold more energy per molecules of glucose oxidized than the most efficient anaerobic pathways
- The ability of O2 to diffuse across biological membranes and to bind heme moieties* in proteins (e.g. hemoglobin and cytochromes) facilitates O2 delivery to systemic organs and mitochondrial electron transfer functions.
what are Heme moieties
*Heme moieties = prosthetic groups, specifically iron-containing porphyrin rings, found in proteins like hemoglobin and cytochromes, crucial for oxygen transport and electron transfer
what do animals require for gas exchange
Animals require large respiratory surfaces for exchange of gases between their cells and the respiratory medium (air or water)
how does gas exchange occur
- Gas exchange takes place by diffusion
- Gases diffuse down pressure (not concentration) gradients in lungs and other organs as result of differences in partial pressure
- Partial pressure is the pressure exerted by a particular gas in a mixture of gases (Dalton’s law)
- This also applies to gases dissolved in liquids (Henry’s law)
how can small animals exchange gases
Diffusion over whole body - capillaries near the surface
Used in small organisms
what are the two mediums animals can extract O2 from, and how do they compare
- Animals can extract O2 from air or water
- In a given volume (and pressure) there is less O2 available in water compared to air
- Water is ~800x denser and 50x more viscous than air, and therefore more difficult to move (”ventilation”)
- O2 solubility decreases with temperature and [solute]
- Obtaining O2 from water requires a much greater effort
what are the stats for O2 in water vs air
O2 partial pressure = 160 mm in air, 160 mm in water (ratio 1:1)
O2 concentration = 210 ml/L in air, 7 ml/L in watert (ratio 30:1)
Density of air = 0.0013 Kg/L and water = 1 Kg/L (ratio 1:770)
Viscosity of air = 0.02 cP, viscosity of water = 1 cP (ration 1:50)
what are gills
Gills are outfoldings of the body that create a large surface area for gas exchange
Gills can be external or internal
How do gills exchange gases
Fish gills use a countercurrent exchange system
Blood flows in the opposite direction to water passing over the gills
Blood is always less saturated with O2 than the water it meets
In fish gills, more than 80-90% of the O2 dissolved in the water is removed as water passes over the gills.
Describe the tracheal system
Consist of a network of branching tubes throughout the body
Supply O2 directly to every body cell
Spiracles are gated to minimize water loss
sacs for air storage
The respiratory and circulatory systems are separate
Larger insects must actively ventilate their tracheal system to meet O2 demands
How do amphibians like frogs breath
An amphibian such as a frog ventilates its lungs by positive pressure breathing, which forces air down the trachea
Frog:
- Air enters pocket of buccal cavity
- Glottis opens, Elastic recoil of lungs and compression of chest wall reduces lung volume, air is forced out of the lungs and out the mouth and nares
- Mouth and nares close, floor of buccal cavity rises, air is pushed into lungs
- Glottis closes, gas exchange occurs in lungs
How do birds breath
Birds have 8 or 9 air sacs that function as bellows that keep air flowing through the lungs
Air passes through the lungs in one direction only
Passage of air through the entire system of lungs and air sacs require two cycles of inhalation and exhalation
Ventilation in birds is highly efficient
Inhalation: Air sacs fill
Exhalation: Air sacs empty; lungs fill
how is the respiratory system kept clean
Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx
This “mucus escalator” cleans the respiratory system and allows particles to be swallowed into the esophagus
How do mammals breath
A system of branching ducts conveys air to the lungs
Air inhaled through the nostrils is filtered, warmed, humidified, and sampled for odours
The pharynx directs air to the lungs and food to the stomach
Swallowing moves the larynx upwards and tips the epiglottis over the glottis in the pharynx to prevent food from entering the trachea
Trachea splits into two bronchi which further divide into bronchioles
How do mammals make vocalizations
Exhaled air passes over the vocal cords in the larynx to create sounds
What can mutations in the CFTR gene do to the respiratory tract
Mutations in cystic fibrosis transmembrane conductance regulator (CFTR) gene results in Cl-/HCO3- imbalances. Low Cl results in the generating of a thick, sticky, mucous lining.
Where are gases exchanged in mammals
- O2/CO2 exchange takes place in alveoli, air sacs at the tops of bronchioles, which have a moist film of the epithelium
- Millions of alveoli: total surface area = 100 m^2 in humans
What are Alveoli like
- Alveoli lack cilia and are susceptible to contamination
- Secrete surfactants (detergent) at the surface of alveoli to break surface tension (help keep shape)
- Preterm babies lack surfactant and artificial surfactants are needed
how do mammals breath
Mammals ventilate their lungs by negative pressure breathing, which pulls air into lungs
Lung volume increases as intercostal muscles and the diaphragm contract
what’s up with lung volume
The tidal volume is the volume of air inhaled with each breath
Maximum tidal volume is the vital capacity
After exhalation a residual volume of air remains in the lung
how do pressure differences affect diffusion in the alveoli vs tissue capillaries
Blood arriving in the lungs has a low partial pressure of O2 and high partial pressure of CO2 relative to air in the alveoli
In alveoli, O2 diffuses into the blood and CO2 diffuses into the air
In tissue capillaries, partial pressure gradient favour diffusion of O2 into the interstitial fluids and CO2 into the blood
how do O2 and CO2 move in the circulatory system
- O2 diffuses down the PO2 gradient
- from alveolar spaces into lung capillaries
- from systemic capillaries to tissues
- CO2 diffuses down the PCO2 gradient
- from tissues to systemic capillaries
- from lung capillaries to alveolar spaces
What are respiratory pigments
Respiratory pigments, proteins that transport Oxygen, greatly increase the amount of oxygen that blood can carry
