Week 20

Question 1

What are two major challenges cetaceans face during diving?

Answer 1

Need to hold breath while diving (up to 60–200 minutes)

Need to withstand increased pressure during deep diving (up to 1,500–2,500 meters)

Question 2

How much lung volume can cetaceans exchange per breath?

Answer 2

Cetaceans: 80–90% of lung volume

Question 3

What allows cetaceans to have quicker gas exchange compared to land mammals?

Answer 3

They can exchange a larger percentage of lung volume per breath.

Question 4

How do cetaceans store oxygen in their bodies?

Answer 4

Muscle myoglobin stores ~35% of the body’s oxygen.

Question 5

How are cetacean airways adapted to diving?

Answer 5

Airways are heavily reinforced with muscle and cartilage, preventing air from being trapped away from alveoli.

Question 6

What is the haemoglobin concentration in cetacean blood compared to land mammals?

Answer 6

Cetaceans: ~60% haemoglobin

Land mammals: ~34% haemoglobin

Question 7

What is expiratory flow like in cetaceans?

Answer 7

Expiratory flow is effort-dependent and can be high even at low lung volumes.

Question 8

Why do cetaceans have a compliant chest wall?

Answer 8

To avoid lung squeeze under pressure.

Question 9

What happens to alveoli during deep dives in cetaceans?

Answer 9

Alveolar collapse occurs to prevent nitrogen absorption.

Question 10

What is cardiorespiratory coupling in bottlenose dolphins?

Answer 10

Exhalation causes heart rate to drop.

Inhalation causes heart rate to increase (tachycardia).

Question 11

What are the benefits of cardiorespiratory coupling in cetaceans?

Answer 11

Quickens gas exchange during inhalation.

Reduces cardiac work during inter-breath intervals.

Question 12

What is lung squeeze in cetaceans and how is it managed?

Answer 12

External pressure increases during deep dives, compressing lungs and risking tissue rupture.

Capillary blood volume increases to counteract increased pressure.

Question 13

What are lamellae in fish gills?

Answer 13

Thin filaments of tissue that provide a large surface area for gas exchange.

Question 14

Why is a large surface area crucial for fish gills?

Answer 14

Oxygen concentration in water is much lower (~1/25th) compared to air, and diffusion is slower.

Question 15

How does water support fish gill structure?

Answer 15

Water supports the floating lamellae; they collapse outside water.

Question 16

What is countercurrent exchange in fish gills?

Answer 16

Blood flows in the opposite direction to water flow, allowing fish to recover less than 90% of oxygen from water.

Question 17

What is ram ventilation?

Answer 17

Fish swim with their mouths open to allow water to flow over the gills.

Question 18

What is buccal pumping?

Answer 18

Fish actively draw in water and pump it over the gills.

Question 19

How do tadpoles breathe?

Answer 19

Using external gills and some pulmonary respiration.

Question 20

What is cutaneous respiration?

Answer 20

Diffusion of O₂ and CO₂ through the skin.

Question 21

What specialized glands support cutaneous respiration in amphibians?

Answer 21

Mucous glands (keep skin moist)

Granular glands

Question 22

Which amphibians rely exclusively on cutaneous respiration?

Answer 22

Lungless salamanders.

Question 23

What contribution do bat wings make to respiration?

Answer 23

Bat wings contribute less than 10% to total respiration.

Question 24

How is the insect respiratory system different from the circulatory system?

Answer 24

It is separate; insects use a network of tracheal tubes to deliver oxygen directly to body cells.

Question 25

What structures allow air to enter an insect's body?

Answer 25

Spiracles, located along the thorax (1 pair per body segment).

Question 26

What is the path of air through the insect tracheal system?

Answer 26

Spiracle valves open and air enters the trachea. Air flows through tracheal tubes to tracheoles. Oxygen dissolves in tracheole liquid and diffuses into adjacent cell cytoplasm. Carbon dioxide diffuses out of cells into tracheoles.

Question 27

What are air sacs in insects used for?

Answer 27

For air storage.

Question 28

How do insects influence airflow through their respiratory system?

Answer 28

By opening and closing spiracles.

Question 29

What is the difference between trachea and tracheole walls?

Answer 29

Trachea walls are thick. Tracheole walls are thin.

Question 30

How is most gas exchange achieved in insects?

Answer 30

Most gas exchange is passive.

Question 31

How are tracheoles specialized for flight muscles in fruit flies?

Answer 31

They supply the flight muscles directly, allowing efficient gas exchange during flight.

Question 32

What are tracheal gills?

Answer 32

Outgrowths that undulate to circulate oxygenated water over the surface during swimming.

Question 33

What is the ventilatory system and how do plants and animals differ in their ventilatory systems?

Answer 33

The ventilatory (respiratory) system is a series of organs and structures for the exchange of gases into and out of an organism. Animals: O₂ into the organism, exchanged with CO₂ which is removed. Plants: CO₂ into the organism, exchanged with O₂ which is removed.

Question 34

What is the overall anatomy of mammalian lungs?

Answer 34

Lungs involve structures for transporting gases like oxygen and carbon dioxide. (Slide included simple CO₂ and O₂ notations — indicates gas exchange.)

Question 35

What are the key parts of the trachea and bronchi and their functions?

Answer 35

Larynx: Holds vocal cords for speech and vocalization. Muscles constrict/relax to produce coughing or clear throat. Tracheal cartilage rings: 16–20 C-shaped rings of hyaline cartilage maintain windpipe structure for free gaseous exchange. Primary bronchi: Splits trachea between two lungs. Secondary bronchi: Multiple bronchial splits leading into alveoli. Trachealis muscle: Smooth muscle connecting cartilage rings and oesophagus, aids in expelling air during coughing.

Question 36

Describe the internal structure of the trachea and the function of its lining.

Answer 36

Thin epithelium lined with multiciliated cells and mucous-producing goblet cells. Cilia move bacteria, mucus, and debris out of the lungs and into the back of the throat.

Question 37

What is the structure of mammalian alveoli and how does it aid gas exchange?

Answer 37

Alveolar sacs: Linked spherical air pockets with a large surface-to-volume ratio for increased gaseous exchange. Pulmonary capillary: Multiple close, single-cell-thick blood vessels pushed against alveolar walls for ease of gaseous exchange; high blood flow rapidly replaces oxygenated blood with deoxygenated blood. Thin alveolar epithelium: Aids rapid gas exchange.

Question 38

Describe the process of breathing in mammals.

Answer 38

Breathing in: Diaphragm contracts and moves downward. Rib cage expands as muscles contract. Air is drawn into the lungs. Breathing out: Diaphragm relaxes and moves upward. Rib cage gets smaller as muscles relax. Air is pushed out of the lungs.

Question 39

What happens in asthma, and what are its symptoms?

Answer 39

Asthma: Long-term inflammatory disease of the airways of the lungs. Characterized by reversible, short-term airflow obstructions. Symptoms: Wheezing Tightness of the chest Shortness of breath Coughing fits Reduced peak and forced expiratory volume Causes: Mixture of genetic and environmental factors (dust, chemical irritants, air pollution, respiratory infections).

Question 40

How is asthma managed?

Answer 40

No complete cure. Trigger identification: Avoid smoke, pets, food allergens, etc. Short-acting beta₂-adrenoceptor agonists (SABA): Used for daily asthma attacks and pre-exercise prevention. Corticosteroids: Reduce asthmatic exacerbation by lowering localized inflammatory response.

Question 41

Describe the mode of action of SABA

Answer 41

Salbutamol binds to β₂ receptors in trachealis and bronchi smooth muscle tissue. β₂ receptors activate adenylate cyclase. Adenylate cyclase converts ATP to cyclic AMP (cAMP). cAMP activates myosin kinase starting a kinase cascade. The kinase cascade blocks Ca²⁺ ion intake, reducing intracellular Ca²⁺ in smooth muscle cells. This reduces bronchial and trachealis smooth muscle constriction, opening the bronchioles.

Question 42

What is pneumonia and how does it affect the lungs?

Answer 42

Pneumonia: Infection-caused inflammation of alveoli. Can be bacterial or viral. Often due to upper respiratory tract infections progressing lower. Bacterial pneumonia (e.g., Streptococcus pneumoniae): Infects spaces between alveoli and pulmonary capillaries. Fills alveoli with pus and fluid as white blood cells attack bacteria.

Question 43

Describe the effect of pneumonia on alveoli tissue.

Answer 43

Normal alveoli: No fluid/debris → easy O₂ and CO₂ exchange. Infected alveoli: Fluid accumulation blocks easy gas exchange.

Question 44

What is cystic fibrosis and how does it affect breathing?

Answer 44

Genetic disorder causing thick mucus buildup in organs, mainly lungs. Leads to difficulty breathing and coughing. Increased risk of respiratory infections. Caused by mutations in CFTR gene → defective CFTR protein. Defective CFTR prevents Cl⁻ ion flow → less fluid mucus → thick mucus blocks cilia clearing.

Question 45

How does cystic fibrosis alter lung tissue and other organs?

Answer 45

Healthy lungs: Relaxed/flexible airway walls, clear airways, thin bronchi walls, healthy bacterial ecosystems. CF-affected lungs: Thick bronchi walls, persistent bacterial infections, blood and mucus in airways, constricted/stiff airway walls. Other affected organs: - Increased bacterial sinusitis infections - Altered sweat (more salty) - Blocked biliary ducts (liver) - Thick mucus in intestines (blocks nutrient absorption) - Blocked pancreatic ducts - Fertility issues (lack of vas deferens, reduced sperm mobility)

Question 46

Why do plants need a ventilatory system? (Part 1)

Answer 46

Plants need ventilatory systems because they are too thick for diffusion alone.

Question 47

Why do plants need a ventilatory system? (Part 2)

Answer 47

Plants use their ventilatory system to move carbon dioxide (CO₂) into the leaf material and oxygen (O₂) out. CO₂ is fixed to produce sugars during photosynthesis, and oxygen is released as a waste product. Plants also require oxygen for respiration.

Question 48

What drives gaseous exchange in plants and what are the challenges?

Answer 48

Gaseous exchange is driven by differences in gas concentrations inside and outside the leaf. Challenges include balancing the uptake of CO₂ for photosynthesis with minimizing water loss. Compare daytime and nighttime gas movement.

Question 49

What are compensation points in plants?

Answer 49

The compensation point is the point at which the rate of photosynthesis equals the rate of respiration. At this point, there is no net loss or gain of CO₂ and O₂.

Question 50

Main movement of gases during the day and night.

Answer 50

During the day: Net movement of CO₂ into the plant. At night: Net movement of O₂ into the plant. Other gases still move, but the majority movement is as stated.

Question 51

How is most of the plant’s need for oxygen met during the day?

Answer 51

Most of the plant’s oxygen needs are met by internal production during photosynthesis.

Question 52

What is the structure of a leaf related to gas exchange?

Answer 52

Mesophyll cells: Involved in gas exchange. Palisade cells: Carry out photosynthesis. Spongy mesophyll cells: Create air pockets for gas movement. Stomata: Pores for gas entry/exit. Guard cells: Control the opening and closing of stomata. Unique feature of guard cells: They possess chloroplasts, unlike lower epidermal cells.

Question 53

How is CO₂ absorbed by plants?

Answer 53

CO₂ diffuses through open stomata into the spongy mesophyll air pockets. Water and O₂ are removed through the stomata. Water is lost via transpiration

Question 54

Why is CO₂ fundamental for plants?

Answer 54

CO₂ is essential for photosynthesis. Plant growth is limited by the concentration of atmospheric CO₂ and the rate of absorption. Atmospheric CO₂ concentration is ~0.04%. About 1900 liters of air are needed to produce 1g of glucose (if photosynthesis were 100% efficient).

Question 55

How is CO₂ absorption maintained in plants?

Answer 55

Atmospheric CO₂ (~0.04%) is higher than internal CO₂ (~0.02%) inside spongy mesophyll, maintaining a gradient. Rapid absorption keeps this gradient active. Spongy mesophyll cells have large surface areas to increase absorption rates.

Question 56

How does CO₂ enter mesophyll cells?

Answer 56

CO₂ crosses the membrane directly and is converted into HCO₃⁻ by carbonic anhydrase. Alternatively, CO₂ is converted to HCO₃⁻ outside cells and actively transported inside with efflux of other negative ions. HCO₃⁻ is then converted back into CO₂ near RubisCO for the Calvin cycle.

Question 57

Overview of CO₂ processing in plants (Calvin Cycle).

Answer 57

Atmospheric CO₂ enters through stomata into spongy mesophyll. CO₂ is converted into HCO₃⁻ to aid absorption and prevent release. CO₂ enters the Calvin cycle via RubisCO. HCO₃⁻ is converted back into CO₂ by carbonic anhydrase.

Question 58

Why don't plants keep their stomata open all the time to maximize CO₂ absorption?

Answer 58

Although maximizing CO₂ would help photosynthesis, keeping stomata open constantly would cause excessive water loss and plant dehydration.

Question 59

How does water loss through stomata compare to CO₂ absorption?

Answer 59

About 100 times more water vapor leaves through stomata compared to CO₂ entering. Therefore, water potential in guard cells regulates stomatal opening and closing.

Question 60

How do stomata open and shut? (Summary)

Answer 60

Water influx into guard cells: Cells become turgid, forcing stomatal pore open. Water efflux from guard cells: Cells deflate, closing the stomatal pore.

Question 61

What regulates stomatal opening?

Answer 61

Blue light is absorbed by chloroplasts in guard cells. Activates H⁺/ATPase proton pumps, altering membrane potential. Causes import of K⁺ and sugars. Lowers water potential, leading to water influx by osmosis via aquaporins, making cells turgid.

Question 62

How do stomata close at night?

Answer 62

No blue light → H⁺/ATPase pump stops. H⁺ ions diffuse back into cells, changing membrane potential. K⁺ ions leave cells. Water exits vacuole, reducing turgidity, causing stomata to close.

Question 63

How do stomata close during drought?

Answer 63

ABA (abscisic acid) is produced. ABA binds receptors, opens Ca²⁺ channels. Activates Cl⁻ active transport and K⁺ channels. Ion efflux causes water to leave guard cells, reducing turgidity, closing stomata.

Question 64

Why is stomatal regulation critical in desert plants?

Answer 64

Constant opening risks dehydration. Only opening stomata at night can limit growth. Plants need special adaptations.

Question 65

What is CAM photosynthesis and how does it work?

Answer 65

CAM (Crassulacean Acid Metabolism) allows night-time gas exchange. Steps: CO₂ absorbed into mesophyll cells at night. CO₂ + H₂O converted to HCO₃⁻ by carbonic anhydrase. HCO₃⁻ phosphorylated by PEPC with PEP into oxaloacetate. Oxaloacetate converted to malate by MDH. Malate stored as malic acid in vacuoles.