Gas Exchange

Question 1

What is Ventilation

Answer 1

The process of bringing fresh air into the alveoli and removing stale air through two stages: Inspiration and Expiration

Maintains the concentration gradient of CO2 and Oxygen between alveoli and blood in capillaries

Question 2

What is Gas Exchange

Answer 2

The process of swapping one gas for another.

Occurs in the alveoli of the lungs

Oxygen diffuses from the alveoli into the capillaries and CO2 diffuses from capillaries to the alveoli

Question 3

What is Cell Respiration

Answer 3

The production of ATP to be used as energy in the cell

Oxygen is used and CO2 is produced

Question 4

Properties of Gas Exchange Surfaces

Answer 4

Permeable: Gases can diffuse freely

Large: SA:V ratio is large

Moist: Surface is covered by layer of moisture so gases can dissolve

Thin: Gases diffuse only short distance, usually one cell thick

Question 5

Importance of Concentration Gradient in Gas Exchange

Answer 5

The steeper the concentration gradient, the faster the diffusion. Concentration gradient should be maintained to allow fast diffusion of gases into alveoli and capillaries

Question 6

How are Concentration Gradients Maintained

Answer 6

Dense network of blood vessels: Capillaries have large surface area for diffusion of gases

Continuous blood flow: Maintains difference in concentration as blood carrying oxygen moves away from lungs and blood carrying CO2 moves to lungs

Ventilation: Ventilation brings oxygen to capillaries and removes CO2

Question 7

Adaptations of Lungs for Gas Exchange / Structure of Lungs

Answer 7

Air enters respiratory system through nose or mouth and passes through the pharynx into the trachea

The air travels down the trachea until it divides into two bronchi which connect into the lungs

The right lung has 3 lobes while the left lung has 2 due to the position of the heart

The bronchi divide into smaller airways called bronchioles which increases surface area

Each bronchiole ends / terminates with a cluster of air sacs called alveoli, where gas exchange with the bloodstream occurs

Question 8

Structure of Alveoli / Adaptations

Answer 8

Have an epithelial (one cell thick) layer to minimize diffusion distance and allow for easier diffusion for respiratory gases

Surrounded by capillary network to increase gas exchange capacity with blood

Roughly spherical in shape to maximize surface area for gas exchange

Internal surface is covered with a layer of fluid to allow for dissolved gases to diffuse better into the bloodstream

Question 9

Adaptations of Alveoli and Advantage

Answer 9

Large numbers of alveoli : Increase surface area for gas exchange

Alveolus is surrounded by capillary network with low oxygen and high CO2 concentration : Allows oxygen and CO2 to diffuse in and out of the blood

Question 10

T1 Pneumocyte and Advantage

Answer 10

Function: Carry out gas exchange
Adaptations: Thin and epithelial

Advantage: Shortens distance for diffusion, allows for rapid diffusion and gas exchange

Question 11

T2 Pneumocyte and Advantage

Answer 11

Function: Secrete solution containing surfactant that creates moist surface inside alveoli

Advantage: Prevents sides of alveolus sticking to each other by reducing surface tension, allows gases to dissolve to make diffusion easier

Question 12

During Inspiration

Answer 12

Muscles Responsible: Diaphragm and External Intercostal

Diaphragm contracts, causing it to flatten and increase volume of thorax

External Intercostal contracts, pulling ribs upward and outward (expanding chest)

Question 13

During Expiration

Answer 13

Muscles Responsible: Abdominal, Diaphragm and Internal Intercostal

Diaphragm relaxes, causing it to curve upwards and reduce volume of thorax

Internal Intercostal contracts, pulling ribs downward and inward (reducing width of chest)

Abdominal muscle contracts and push the diaphragm upwards during forced exhalation

Question 14

Partial Pressure

Answer 14

The pressure exerted by an individual gas in a mixture of gases

Question 15

Hemoglobin VS Myoglobin

Answer 15

Similarities: Both molecules transport oxygen and contain iron at the center of a heme group

Found in blood : Found in muscle tissue

Has 4 heme groups : Has 1 heme group

Carries up to 4 oxygen : Carries 1 oxygen

Lower oxygen affinity at partial pressure :
Higher oxygen affinity at partial pressure

pH sensitive : Not pH sensitive

Question 16

Fetal Hemoglobin

Answer 16

Has 4 heme groups therefore carries 4 oxygen molecules thus higher oxygen affinity than adult hemoglobin

Oxygen affinity is vital to allow for fetus to obtain oxygen from mother at placenta

Oxygen is transferred from adult hemoglobin to fetal

Baby has no myoglobin due to no muscle mass

After birth, baby produces adult hemoglobin which gradually replaces fetal hemoglobin

Question 17

Adult Hemoglobin

Answer 17

Has 4 heme groups therefore carries 4 oxygen molecules

Initial uptake of one oxygen molecule facilitates further uptake of other oxygen molecules

Question 18

Bohr Shift

Answer 18

Explains the increased release of oxygen by hemoglobin in respiring tissues

Occurs when there is lower pH to promote release of oxygen in respiring heart muscle

Increased exercise or metabolism leads to increased respiration, which causes greater release of CO2 which increases partial pressure

Increases acidity and lowers blood pH which shifts oxygen to the right

Hydrogen ions released bind to hemoglobin to decrease affinity for oxygen

Saturation of hemoglobin occurs at higher partial pressures of oxygen so it can release oxygen at higher partial pressures

Question 19

Haldane Effect

Answer 19

Deoxygenated blood has an increased capacity to carry CO2

Oxygenated blood has a decreased capacity to carry CO2

Question 20

Oxygen Dissociation Curve

Answer 20

Both sigmoid shapes

Fetal hemoglobin is at the left adult is at the right