Gas Exchange Flashcards
Requirement for gas exchange
Large, moist respiratory surfaces
Gills
Outfoldings of the body surface
Aquatic animals (fish, mollusks, crustaceans)
Effectiveness increased by ventilation and countercurrent flow of blood and water
Tracheal system
Tiny branches that penetrate the body
Insects
Air flow: trachea -> tracheole (branch of trachea) -> body cell
Can go from trachea to air sac (storage of air)
Air flow through mammalian respiratory system
Nostrils -> pharynx -> trachea -> bronchi (2 main branches of trachea into lungs- 1 branch per lung) -> bronchioles (branches of bronchi) -> alveoli
Alveoli: dead ends where gas exchange occurs
How a mammal breathes
Negative pressure breathing: lung volume increases as the rib muscles and diaphragm contract, pulling air in
Breathing control systems in humans
2 regions in brain: medulla oblongata and pons
Medulla oblongata
Regulation of rate and depth of breathing in response to pH changes in the cerebrospinal fluid and to match metabolic demands
Sensors in aorta and carotid arteries
Monitor O2 and CO2 concentrations in the blood
Exert secondary control over breathing
Diffusion of CO2 and O2
Diffuse from region of higher partial pressure to region of lower partial pressure
Respiratory pigments
Proteins that transport oxygen
Greatly increase the amount of oxygen that blood can carry
Hemoglobin
Respiratory pigment of almost all vertebrates
Contained in erythrocytes (red blood cells)
Cooperativity
Binding of O2 to one subunit of hemoglobin molecule induces the other subunits to bind O2 with more affinity
Loading and unloading of O2
1st oxygen molecule attaches to iron -> hemoglobin changes shape and can pick up each subsequent oxygen molecule more easily
Hemoglobin releases oxygen molecule -> strength of bond between iron and remaining oxygen molecules becomes progressively weaker
Dissociation curve for hemoglobin
Cooperative O2 binding and release
Hemoglobin retains less O2 at lower pH (higher CO2 concentration)- Bohr shift
x axis: partial pressure of O2
y axis: % O2 saturation of hemoglobin
CO2 transport in cells
CO2 produced by body tissues diffuses into interstitial fluid and plasma
Most of CO2 diffuses into red blood cells and is picked up and transported by hemoglobin
CO2 reacts with water in red blood cells, making H2CO3 (catalyzed by carbonic anhydrase)
H2CO3 dissociates into bicarbonate ion and hydrogen ion
Hemoglobin binds most of H+, preventing Bohr shift
Bicarbonate diffuses into plasma and is carried by bloodstream into lungs
Bicarbonate combines with H+, reforming H2CO3
CO2 formed from H2CO3 is unloaded from hemoglobin and diffuses into interstitial fluid
CO2 diffuses into alveolar space and is expelled during exhalation
Reduction of CO2 concentration in plasma drives breakdown of H2CO3 into CO2 and water in red blood cells
