Lesson Worksheet: The Human Respiratory System Biology

In this worksheet, we will practice describing the structure of the lungs and explaining how they are adapted for efficient gas exchange.


What gas is transported out of the bloodstream and into the lungs to be exhaled?

  • ASulfur dioxide
  • BCarbon monoxide
  • CCarbon dioxide
  • DNitrogen


What is the primary purpose of the lungs in the gas exchange system?

  • ATo pump oxygenated blood around the body
  • BTo break down excess glucose for energy
  • CTo bind to oxygen from the atmosphere
  • DTo exhale oxygen
  • ETo inhale and exhale air


What gas is taken in by the lungs and transported around the body in red blood cells?

  • ACarbon oxide
  • BSulfur dioxide
  • COxygen
  • DNitrogen


Which of the following correctly outlines the movement of oxygen from the atmosphere into the body?

  • AAtmosphere trachea alveoli capillaries bloodstream bronchi bronchioles
  • BAtmosphere trachea bronchi bronchioles alveoli capillaries bloodstream
  • CAtmosphere alveoli trachea bronchi bronchioles capillaries bloodstream
  • DAtmosphere trachea bronchi bronchioles bloodstream alveoli capillaries
  • EAtmosphere bronchi bronchioles trachea alveoli capillaries bloodstream


The walls of the alveoli and the capillaries are very thin. Why is this an advantage?

  • AIt provides a small surface area for reactions to occur.
  • BIt provides a short diffusion pathway for gas exchange.
  • CIt allows alveoli to expand and contract easily.
  • DIt prevents blood from clotting in the capillaries.
  • EIt prevents microbes from entering the alveoli.


What protein does oxygen bind to in red blood cells?

  • AGlobulin
  • BHemoglobin
  • CInsulin
  • DHistone
  • EIronin


An alveolus has a large surface area relative to its volume. Which of the following best describes the advantage of this?

  • AA large surface area allows the temperature to be regulated more easily.
  • BA large surface area allows more diffusion to occur.
  • CA large surface area prevents the entry of microbes or pathogens.
  • DA large surface area provides more space for the enzyme-controlled reactions to take place.


The diagram provided shows a basic outline of the human lungs, with parts magnified.

Which number points to the trachea?

Which number points to the alveoli?


What is the result of the decrease in air pressure in the lungs?

  • AAir is pulled in.
  • BThe volume of the lungs decreases.
  • CAir is forced out.
  • DThere is no overall movement of air.


The table shows the typical composition of inhaled and exhaled air.

GasPercentage of Air Breathed InPercentage of Air Breathed Out
Carbon dioxide0.04%
Other (including noble gases and water vapor)1%3%

Calculate the percentage of oxygen that is typically breathed in.

Calculate the percentage of carbon dioxide that is typically breathed out.

This lesson includes 25 additional questions for subscribers.

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