BIO* - Biology BIO* M121 Lecture Notes - Lecture 4: Cellular Respiration, Gas Exchange, Trachea
Charlie Kent
Bio M121
Summer 2017
General Bio
● Overview
○ Ventilation and gas exchange are accomplished by the respiratory system
○ The circulatory system is responsible for moving gases and other materials around
the body
■ Gas exchange between the environment and cells is based on diffusion
■ O2 is high in the environment and low in tissues
■ CO2 is high in tissues and low in the environment
■ O2 thus tends to move from the environment into tissues and CO2 tends to
move from tissues into the environment
● Gas Exchange
○ Cells must obtain O2 and expel CO2 continuously to support ATP production by
mitochondria
■ O2 is required for cellular respiration
■ CO2 is produced by cellular respiration
○ In addition, these gases (along with wastes, nutrients, and other types of
molecules) must be transported throughout the body
○ Gas exchange facilitates these processes
● Gas Exchange: Four Steps
○ Ventilation
■ Air or water moves through a specialized gas-exchange organ, such as
lungs or gills
○ Gas exchange
■ Diffusion of O2 and CO2 between air or water and the blood at the
respiratory surface
○ Circulation
■ Dissolved gases are transported throughout the body (along with nutrients,
etc.)
○ Cellular respiration
■ Cells use O2 and produce CO2
■ In tissues where respiration leads to low O2 and high CO2 levels, gas
exchange occurs between blood and cells
● Gas exchange involves ventilation, circulation, and respiration
○ In animals, O2 and CO2 are exchanged across the surface of a lung, gill, skin, or
some other gas exchange organ
○ In many species these gases are then transported to and from cells – where gas
exchange again takes place – in a fluid tissue such as blood
● Gases in air
○ 76% N2, 21% O2, 3% other gases (CO2, Ar, etc.)
○ Fewer molecules are present at higher elevations
Document Summary
Ventilation and gas exchange are accomplished by the respiratory system. The circulatory system is responsible for moving gases and other materials around the body. Gas exchange between the environment and cells is based on diffusion. O2 is high in the environment and low in tissues. Co2 is high in tissues and low in the environment. O2 thus tends to move from the environment into tissues and co2 tends to move from tissues into the environment. Cells must obtain o2 and expel co2 continuously to support atp production by mitochondria. In addition, these gases (along with wastes, nutrients, and other types of molecules) must be transported throughout the body. Air or water moves through a specialized gas-exchange organ, such as lungs or gills. Diffusion of o2 and co2 between air or water and the blood at the respiratory surface. Dissolved gases are transported throughout the body (along with nutrients, etc. )