B3 exam qs Flashcards
(a) Describe and explain one feature of the alveolar epithelium that makes the epithelium well
adapted as a surface for gas exchange.
- Permeable;
- Allows diffusion of oxygen/carbon dioxide;
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide
between the blood and the alveoli.
- Less carbon dioxide exhaled
- (So) reduced diffusion/concentration gradient
- less CO2 moving out of blood
Explain the advantage for larger animals of having a specialised system that facilitates
oxygen uptake.
Large(r) organisms have a small(er) surface area:volume (ratio)
- Overcomes long diffusion pathway
Suggest how the environmental conditions have resulted in adaptations of systems using
Model A rather than Model B.
- Water is dense(r) (than air);
- (So) water supports the systems/gills;
A student studied Figure 2 and concluded that the fish gas exchange system is more
efficient than the human gas exchange system.
Use Figure 2 to justify this conclusion.
- In fish, blood leaving (V) has more oxygen than water leaving (E);
- (But) in humans, blood leaving (V) has less oxygen than air leaving (E);
- Difference in oxygen (concentration) between artery and vein is greater in
fish than in humans; - (So) fish remove a greater proportion from the oxygen they take in
Explain how the counter-current principle allows efficient oxygen uptake in the fish gas
exchange system
- Blood and water flow in opposite directions;
- Diffusion/concentration gradient (maintained) along (length of)
lamella/filament;
Describe and explain the mechanism that causes lungs to fill with air
1. Diaphragm contracts and external intercostal muscles contract;
2. Causes volume increase and pressure decrease;
3. Air moves down a pressure gradient
Describe and explain the advantage of the counter-current principle in gas exchange
across a fish gill.
- Water and blood flow in opposite directions;
- Maintains diffusion gradient of oxygen
- oxygen concentration always higher in water
- diffusion along length of gill
Describe the pathway taken by an oxygen molecule from an alveolus to the blood.
- (Across) alveolar epithelium;
- Endothelium / epithelium of capillary;
Describe and explain the mechanism that causes forced expiration.
- Contraction of internal intercostal muscles;
- Relaxation of diaphragm muscles / of external intercostal muscles;
- Causes decrease in volume of chest / thoracic cavity;
- Air pushed down pressure gradient.
The people in group B were recovering from an asthma attack.
Explain how an asthma attack caused the drop in the mean FEV shown in the figure above.
- Muscle walls of bronchi / bronchioles contract;
- Walls of bronchi / bronchioles secrete more mucus;
- Diameter of airways reduced;
- (Therefore) flow of air reduced.
Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange.
- Tracheoles have thin walls so short diffusion distance to cells;
- Highly branched / large number of tracheoles so short diffusion distance to
cells; - Highly branched / large number of tracheoles so large surface area (for gas
exchange);
Explain how the presence of gills adapts the damselfly to its way of life.
- Damselfly larvae has high(er) metabolic / respiratory (rate);
- (So) uses more oxygen
Suggest two ways the student could improve the quality of her scientific drawing of this gill.
- Don’t use shading;
- Only use single lines
- Don’t cross label lines;
- Add magnification / scale (bar);
Name the structure through which gases enter and leave the body of an insect
spiracle
Name the small tubes that carry gases directly to and from the cells of an insect.
Tracheole/trachea
Explain the movement of oxygen into the gas exchange system of an insect when it is at
rest
- Oxygen used in (aerobic) respiration;
- (so) oxygen (concentration) gradient established
- (so) oxygen diffuses in
Using information from the diagram, suggest what stimulates the spiracles to open.
increasing carbon dioxide concentration
) Explain what causes the oxygen concentration in the tracheae to fall when the spiracles are
closed.
(oxygen is used in) respiration therefore diffuses (from tracheae) to tissues;
oxygen unable to enter organism;
The insect lives in dry conditions. Suggest an advantage of the pattern of spiracle
movements shown in the diagram
spiracles not open all the time;
therefore there is less water loss
Describe how the structure of the insect gas exchange system:
* provides cells with sufficient oxygen
* limits water loss (5 marks)
- Spiracles (lead) to tracheae (that lead) to tracheoles;
- Open spiracles allow diffusion of oxygen from air
- Tracheoles are highly branched so large surface area
- Tracheole (walls) thin so short diffusion distance (to cells)
- Tracheole walls are permeable to oxygen;
- Spiracles close (eg.during inactivity) preventing water loss
Describe how humans breathe in and out.
Breathing in
1. Diaphragm (muscles) contract and diaphragm flattens;
- External intercostal muscles contract and ribcage pulled up/out;
- (Causes) volume increase and pressure decrease in thoracic cavity
Breathing out
4. Diaphragm (muscles) relaxes and internal intercostal muscles contract;
5. (Causes) volume decrease and pressure increase in thoracic cavity
Describe and explain how the countercurrent system leads to efficient gas exchange
across the gills of a fish
- water and blood flow in opposite directions
- maintains concentration gradient
- oxygen concentration always higher in water
- diffusion along length of whole gill
The volume of water passing over the gills increases if the temperature of the water
increases. Suggest why.
- Increased respiration
- Less oxygen dissolved in water
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.
- Many lamellae / filaments so large surface area;
- Thin (surface) so short diffusion pathway
Explain how the counter current mechanism in fish gills ensures the maximum amount of
the oxygen passes into the blood flowing through the gills.
- water and blood flow in opposite directions
- maintains diffusion gradient of oxygen
- oxygen concentration always higher in water
- diffusion along whole length of gill
A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted
for efficient gas exchange.
- Large surface area provided by lamellae / filaments increases diffusion
- Thin epithelium / distance between water and blood;
- Water and blood flow in opposite directions / countercurrent;
- (Point 4) maintains concentration gradient (along gill)
as oxygen always has higher concentration in water - Circulation replaces blood saturated with oxygen;
- Ventilation replaces water (as oxygen removed);
The concentration of oxygen is higher in the surface waters than it is in water close to the
seabed. Suggest why.
Mixing of air and water (at surface);
Air has higher concentration of oxygen than water;
Diffusion into water;
Plants / seaweeds near surface / in light;
Produce oxygen by photosynthesis
Describe and explain the mechanism that causes forced expiration
- Contraction of internal intercostal muscles;
- Relaxation of diaphragm muscles / of external intercostal muscles;
- Causes decrease in volume of chest / thoracic cavity;
- Air pushed down pressure gradient.
The people in group B were recovering from an asthma attack.
Explain how an asthma attack caused the drop in the mean FEV shown in the figure
below.
- Muscle walls of bronchi / bronchioles contract;
- Walls of bronchi / bronchioles secrete more mucus;
- Diameter of airways reduced;
- (Therefore) flow of air reduced.
Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs.
- Trachea and bronchi and bronchioles;
- Down pressure gradient;
- Down diffusion gradient;
- Across alveolar epithelium.
Explain how the body shape of a Weddell seal is an adaptation to living in a
cold environment.
Small SA:VOL
retains more heat
what causes the thoractic cavity to increase
external intercostal muscles contract
ribs move up and out
diaphragm contracts and moves down
what causes the thoractic cavity to decrease
external intercostal muscles relax
ribs move down and in
diaphragm relaxes and moves up
what happens to the pressure inside the thoractic cavity when inhaling
decreases
what happens to the volume of the thoractic cavity when exhaling
decreases
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.
- Many alveoli and alveoli walls folded provide a large surface area;
- Many capillaries provide a large surface area;
- So fast diffusion;
- Alveoli and capillary walls are thin so short distance between alveoli and blood;
- Flattened epithelium;
- So short diffusion distance so fast diffusion;
- Ventilation / circulation maintains a diffusion gradient so fast diffusion;
Describe the gross structure of the human gas exchange system and how we breathe in and out.
- trachea, bronchi, bronchioles, alveoli;
- Breathing in - diaphragm contracts and external intercostal muscles contract;
- Causes volume increase and pressure decrease in thoracic cavity to below atmospheric, resulting in air moving in;
- Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
- Causes volume decrease and pressure increase in thoracic cavity to above atmospheric, resulting in air moving out;
what happens to the volume of the thoracic cavity when INHALING
increases
what happens to the pressure inside the thoractic cavity when EXHALING
increase
whats tidal volume
vol of air taken into the lungs during each breath when at rest
what is pulmonary ventilation rate
how do you calculate it
volume of air taken into the lungs during 1 min
pulmonary rate (dm3min-1) = tidal volume (dm3) x breathing rate (min-1)
