Gas exchange

Question 1

What is cellular metabolism (catabolism)?

Answer 1

The process that requires oxygen and produces carbon dioxide.

Question 2

What is gas exchange (respiration)?

Answer 2

The process of taking up oxygen and releasing carbon dioxide.

Question 3

Why do complex organisms need efficient gas exchange?

Answer 3

Due to their high energy demands and the challenge of delivering oxygen to cells deep within the body.

Question 4

What are the two types of respiration?

Answer 4

• External respiration (gas exchange with the environment)
• Internal respiration (gas exchange between blood and body cells)

Question 5

How do gases move?

Answer 5

From areas of high partial pressure to areas of low partial pressure.

Question 6

What is Fick’s Law of Diffusion?

Answer 6

Vx = D x A x (P1-P2) / X

Question 7

Define the variables in Fick’s Law.

Answer 7

• Vx = rate of diffusion
• D = diffusion constant
• A = surface area
• P1-P2 = partial pressure gradient
• X = membrane thickness

Question 8

How does a large surface area affect gas exchange?

Answer 8

Increases diffusion.

Question 9

How does a thin respiratory surface affect gas exchange?

Answer 9

Increases diffusion.

Question 10

How does a steep partial pressure gradient affect gas exchange?

Answer 10

Increases diffusion.

Question 11

What are the two respiratory media?

Answer 11

• Air
• Water

Question 12

What is the oxygen concentration in air?

Answer 12

Higher (21%).

Question 13

Is oxygen diffusion faster in air or water?

Answer 13

Air.

Question 14

Does ventilation require more energy in air or water?

Answer 14

Water.

Question 15

What affects oxygen solubility in water?

Answer 15

• Temperature
• Salinity

Question 16

What is a respiratory surface?

Answer 16

Where gas exchange occurs.

Question 17

Why must respiratory surfaces be moist?

Answer 17

To facilitate diffusion.

Question 18

How do multicellular organisms compensate for decreasing surface area to volume ratio?

Answer 18

They evolve specialized respiratory surfaces.

Question 19

What are the four main types of respiratory surfaces?

Answer 19

• Body surfaces
• Tracheal systems
• Gills
• Lungs

Question 20

Describe gas exchange using body surfaces.

Answer 20

Gas exchange occurs directly through the skin; suitable for small animals in aquatic or moist environments.

Question 21

Give examples of animals that use body surfaces for gas exchange.

Answer 21

• Sponges
• Cnidarians
• Flatworms
• Some annelids

Question 22

Describe tracheal systems.

Answer 22

A network of internal tubes (tracheae) that deliver air directly to cells, found in insects and some other arthropods.

Question 23

What are spiracles?

Answer 23

Openings to the outside for air entry in tracheal systems.

Question 24

What are tracheoles?

Answer 24

Fine branches of the tracheal system that reach individual cells.

Question 25

Describe gills.

Answer 25

Specialized respiratory structures in aquatic animals that increase the surface area for gas exchange with water.

Question 26

Describe lungs.

Answer 26

Internal respiratory organs in terrestrial vertebrates that provide a large surface area for gas exchange while minimizing water loss.

Question 27

What do fish use for gas exchange?

Answer 27

Gills.

Question 28

How does water flow over the gills?

Answer 28

Oxygen diffuses from the water into the blood, while carbon dioxide diffuses from the blood into the water.

Question 29

What is countercurrent exchange?

Answer 29

Maximizes oxygen uptake from water in fish gills.

Question 30

Why is oxygen poorly soluble in water?

Answer 30

Blood alone cannot carry enough oxygen.

Question 31

What are respiratory pigments?

Answer 31

Increase the oxygen-carrying capacity of blood.

Question 32

What is hemoglobin?

Answer 32

The respiratory pigment in vertebrates.

Question 33

What does hemoglobin contain?

Answer 33

Iron (Fe), which binds to oxygen.

Question 34

How many oxygen molecules can each hemoglobin molecule carry?

Answer 34

Four.

Question 35

How is oxygen transported in blood?

Answer 35

* Dissolved in plasma (small amount) * Bound to hemoglobin (majority)

Question 36

What is the oxygen-hemoglobin dissociation curve?

Answer 36

Shows the relationship between the partial pressure of oxygen (PO2) and the percentage saturation of hemoglobin with oxygen.

Question 37

What is P50?

Answer 37

The PO2 at which hemoglobin is 50% saturated (indicates hemoglobin's affinity for oxygen).

Question 38

How does decreased pH affect hemoglobin's affinity for oxygen?

Answer 38

Decreases it (Bohr effect).

Question 39

How does increased temperature affect hemoglobin's affinity for oxygen?

Answer 39

Decreases it.

Question 40

How does increased PCO2 affect hemoglobin's affinity for oxygen?

Answer 40

Decreases it.

Question 41

How is carbon dioxide transported in blood?

Answer 41

* Dissolved in plasma * Bound to hemoglobin (carbaminohemoglobin) * As bicarbonate ions

Question 42

How are bicarbonate ions formed?

Answer 42

Carbon dioxide enters red blood cells and is converted to carbonic acid by carbonic anhydrase; carbonic acid dissociates into hydrogen ions and bicarbonate ions.

Question 43

What challenge do terrestrial animals face regarding gas exchange?

Answer 43

Balancing gas exchange with water loss.

Question 44

What is the main cause of water loss in terrestrial animals?

Answer 44

Evaporation.

Question 45

What factors influence evaporative water loss?

Answer 45

* Water content of the atmosphere (humidity) * Temperature * Air movement * Barometric pressure * Surface area