University:
University of Virginia
Course:
BIOL 2200 | Introduction to Biology II: Organisms & Evolution
Academic year:

2024
Views:

80

Pages:

6
Author:

Zoe C.

33: respiration Friday, April 19, 2024 1:28 PM gas exchange • uptake of molecular O2 from the environment and the discharge of CO2 to the environment • gases move from areas of high partial pressure to areas of low partial pressure • gases diffuse across a moist respiratory surface • rate of diffusion related to surface area and distance mechanisms of gas exchange • all animals require O2 for cellular respiration • what factors influence the organs and mechanisms of gas exchange? gas exchange in insects • tracheae: air tubes branching throughout the body gas exchange in insects • tracheae: air tubes branching throughout the body ○ connected to environment by pores ○ branches found close to every cell • O2/CO2 transfer completed by tracheae ○ separate from circulatory system ○ hemolymph distributes nutrients, collects waste gas exchange in fish • water contains less O2 than air • gills have a large surface area for gas exchange • gas exchange maximized by countercurrent flow ○ gradient increases diffusion rate of gases between blood and gills gas exchange in tetrapods gas exchange in tetrapods • lungs are the primary/sole gas exchange organ ○ except in lungless salamanders breathing • to maintain high O2 and low CO2 at the respiratory surface • different strategies for ventilating the lungs ○ structural differences ○ differences in efficiency breathing in amphibians • lower lung surface area than amniotes • use positive pressure breathing ○ lowers floor of throat, contrasts throat muscles ○ pushes air from oral cavity into their lungs breathing in birds • air sacs act as bellows to keep air flowing breathing in birds • air sacs act as bellows to keep air flowing • 2 cycles of inhalation/exhalation for air to complete circuit • air flow is unidirectional ○ fresh air and O2-reduced air do not mix breathing in mammals • negative pressure breathing • inhalation: ○ muscular contractions expand thoracic cavity ○ lower pressure in lungs ○ air rushes in • exhalation: ○ muscular relaxations condense thoracic cavity ○ greater pressure in lungs ○ air forced out distributing oxygen: hemoglobin • hemoglobin has 4 subunits; each has a heme group with an iron atom ○ each iron atom binds one O2 molecule • binding of O2 increases affinity of hemoglobin for more O2 • CO2 production promotes O2 unloading ○ change in blood pH decreases affinity for O2 removing carbon dioxide • CO2 is a waste product of cellular respiration ○ most of converted to bicarbonate (HCO3-) in erythrocytes, then travels in plasma to lungs • converted back to CO2 in lungs, then diffuses out of blood and into alveoli to be removed regulating gas exchange in mammals • breathing controlled by the medulla oblongata • pH of cerebrospinal fluid indicates CO2 level ○ H+ from bicarbonate reaction lowers pH • as metabolic activity increases, a decrease in pH leads to signal to increased breathing