Gas exchange

• What is a gas exchange surface?

  The surface over which gas exchange takes place
• By which process are gases exchanged?

  Diffusion
• Name the gas exchange surface found in animals, plants, and fish.

  Gills in fish, lungs in animals, and stomata in plants
• Why do animals carry out gas exchange?

  To obtain oxygen and remove carbon dioxide
• Why do plants carry out gas exchange?

  To obtain carbon dioxide for photosynthesis and release oxygen
• Define surface area.

  The total area of the surface of an object
• Describe how surface area changes as an organism increases in size.

  As size increases, the surface area becomes smaller in comparison to the volume
• Describe the surface area to volume ratio of a unicellular organism.

  Unicellular organisms have a high surface area to volume ratio
• Describe how the surface area to volume ratio changes as an organism increases in size.

  The surface area to volume ratio decreases as an organism increases in size
• How do large multicellular organisms allow efficient exchange of substances with their environment?

  They adapt gas exchange surfaces to increase surface area
• State the role of the circulatory system in mammals.

  To transport gases, nutrients, and waste products
• Describe how diffusion distance is kept short in diving organisms.

  By having thin exchange surfaces
• Recall which type of molecules can diffuse across the phospholipid bilayer.

  Small nonpolar molecules
• Describe the phospholipid bilayer.

  A double layer of phospholipids with hydrophilic heads and hydrophobic tails
• Explain how diffusion distance affects gas exchange.

  A shorter diffusion distance increases the rate of gas exchange
• Define concentration gradient.

  The difference in concentration of a substance across a space
• Explain how the concentration gradient affects gas exchange.

  A greater concentration gradient increases the rate of gas exchange
• Calculate the SA:VOL ratio for animal A and B.

  Specific calculations are needed for each animal
• Determine why animal A does not need a circulatory system but animal B does.

  Animal A has a sufficient surface area to volume ratio for diffusion
• What is Fick's Law of Diffusion?

  The rate of diffusion is proportional to surface area, concentration difference, and inversely proportional to membrane thickness
• What causes the rate of diffusion to double?

  Doubling the surface area or concentration difference
• What causes the rate of diffusion to halve?

  Doubling the membrane thickness
• Calculate the effectiveness of the uptake of oxygen by the lungs for an individual with emphysema.

  Use Fick's Law with given values
• Why will the individual with emphysema tire more easily than a healthy individual?

  Due to reduced surface area for gas exchange