3.2 Gas exchange Flashcards
What is breathing?
Movement of air into and out of the lungs.
What is ventilation?
Scientific word for breathing.
What is respiration?
Chemical reaction to release energy in the form of ATP.
What is gas exchange?
The diffusion of oxygen from the air into the alveoli into the blood and of carbon dioxide from the blood into the air in the alveoli.
What does the trachea contain in mammals?
C-shaped rings of cartilage, which are tough in order to support the trachea and keep it open.
What does the trachea branch into in mammals?
The 2 bronchi.
What does the bronchi branch into in mammals?
Several bronchioles in each lung.
What are at the end of the bronchioles?
The alveoli.
What are the internal intercostal muscles and external intercostal muscles?
Antagonistic.
What does it mean that the internal intercostal muscles and external intercostal muscles are antagonistic?
When one contracts, the other relaxes.
What does the external intercostal muscles contracting lead to?
Inhalation.
What does the internal intercostal muscles contracting lead to?
Exhalation.
What happens to the external intercostal muscles during inhalation?
They contract - pulling the ribs up and out.
What happens to the internal intercostal muscles during inhalation?
They relax.
What happens to the diaphragm during inhalation?
It contracts and moves downwards.
What happens to the volume in the lungs during inhalation?
Increase.
What happens to the pressure in the lungs during inhalation?
It decreases - meaning it is lower than the atmospheric pressure.
What happens during inhalation due to the pressure in the lungs being lower than the atmospheric pressure?
Air moves into the lungs.
What happens to the internal intercostal muscles during exhalation?
They contract, pulling the ribs down and in.
What happens to the external intercostal muscles during exhalation?
They relax.
What happens to the diaphragm during exhalation?
It relaxes, and returns to the dome position.
What happens to the volume in the lungs during exhalation?
It decreases.
What happens to the pressure in the lungs during exhalation?
It increases - meaning it is higher than atmospheric pressure.
What happens during exhalation due to the pressure in the lungs being higher than the atmospheric pressure?
Air moves out of the lungs.
What are alveoli surrounded by?
Capillaries.
Is the alveolar wall thick or thin?
One-cell thick.
Is the capillary wall thick or thin?
One-cell thick.
Is there a concentration gradient between the alveoli and the capillary?
Yes: high O2 in alveoli and low O2 in capillary; low CO2 in alveoli and high CO2 in capillary.
What are the adaptations of alveoli for surface area?
There are many alveoli in each lung = high surface area.
What are the adaptations of alveoli for diffusion distance?
Alveoli epithelium cells are only 1 cell thick = short diffusion distance.
What are the adaptations of alveoli for concentration gradient?
Each alveolus is surrounded by a capillary network to remove exchanged gases = maintains a concentration gradient.
How is lung capacity measured?
By a spirometer.
What is the tidal volume?
The volume of air that enters and leaves the lungs at a normal resting breath.
What is normally the tidal volume?
0.5 dm^3.
What is the vital capacity?
The maximum volume of air that can be breathed in or out.
What is the residual volume?
Volume of air left in the lungs after maximum exhalation.
What is the total lung capacity?
Vital capacity + residual volume.
What is normally the total lung capacity?
5-6 dm^3.
What is pulmonary ventilation?
The total volume of air that is moved into the lungs during one minute.
What are the units for pulmonary ventilation?
dm^3 min^-1.
What is the equation for pulmonary ventilation?
Pulmonary ventilation = tidal volume x ventilation rate.
How do bronchitis and asthma affect gas exchange?
- Reduce the lumen size of the bronchioles.
- Meaning less air can travel to the alveoli.
- Means there is a smaller concentration gradient.
- And less oxygen for gas exchange.
How does emphysema affect gas exchange?
- Alveoli walls begin to break down.
- Meaning there are far fewer in each lung + are much larger sacs.
- Means there is a small surface area for gas exchange.
- Reducing the amount of O2 diffusing into the lungs and the amount of CO2 diffusing out of the lungs.
How does pulmonary fibrosis affect gas exchange?
- Breakdown of alveoli + causes thick alveolar walls.
- Means there is a smaller surface area + alveoli cannot expand as much (due to thicker wall).
Does correlation always prove causation?
No.
If you state there is a correlation between data, what can you argue for the against?
There is no correlation coefficient statistic.
Do fish have a small or large surface area: volume ratio?
Small.
Why do fish require a gas exchange surface area?
They have a small surface area: volume ratio.
What is Fick’s law?
(Surface Area x Concentration Gradient)/Thickness = rate of diffusion.
What are the 3 key features in every gas exchange surface?
- Large surface area: volume.
- Short diffusion distance.
- Maintained concentration gradient.
How many layers of gills are there on each side of a fish’s head?
4.
What are fish’s gills made up of?
Stacks of gill filaments.
What is each gill filament covered with?
Gill lamellae.
What angle are the gill lamellae at on the filaments?
90 degrees.
Where does diffusion of gases happen on a fish’s gills?
The gill lamellae.
What are the adaptations for gas exchange in fish - surface area?
- Large surface area: volume ratio.
- Created by the many gill filaments covered in many gill lamellae.
What are the adaptations for gas exchange in fish - diffusion distance?
- Short diffusion distance.
- Due to a capillary network in every lamellae.
- And very thin gill lamellae.
What are the adaptations for gas exchange in fish - concentration gradient?
- Large concentration gradient maintained.
- By the countercurrent flow mechanism.
How does gas exchange actually happen in fish?
- When fish open their mouth, water rushes in and over the gills.
- And then out through a hole in the sides of their head.
What is the countercurrent exchange principle?
When water flows over the gills in the opposite direction to the flow of blood in the capillaries.
What does the countercurrent flow mechanism ensure?
- That an equilibrium is not reached.
- Meaning there is never the same concentration of oxygen in the blood, as there is in the water.
Why is it beneficial for gas exchange in fish that an equilibrium is not reached?
Means diffusion can occur across the entire length of the gill lamellae.
What does the countercurrent flow mechanism ensure?
Ensures a diffusion gradient is maintained across the entire length of the gill lamellae.
Do insects have an exoskeleton, and what is it made of?
Yes: made of chitin, a hard fibrous material for protection, and contains a lipid layer to prevent water loss.
What do insects have instead of lungs?
A tracheal system.
Where does water evaporate from in insects?
Of the surface.
What do insects have to balance?
Being able to exchange gases with reducing the amount of water loss.
What are insect adaptations to reduce water loss - surface area?
Insects have a small surface area to volume ratio where water can evaporate from.
What are insect adaptations to reduce water loss - exoskeleton?
- Insects have a waterproof exoskeleton.
- Due to the lipid layer -> which is impermeable to water.
- Means water can only evaporate through the spiracles.
What are insect adaptations to reduce water loss - spiracles?
- Tiny holes in the insect’s abdomen.
- Where gases can enter and exit + water can evaporate from.
- Can open and close to reduce water loss.
What are the 3 structures in the tracheal system?
Trachea, tracheoles, and spiracles.
What are the spiracles?
- Round, valve-like openings.
- That run along the length of the abdomen.
- O2 and CO2 can enter + leave via the spiracles.
- The trachea can attach to these openings.
What is the trachea in insects?
- Network of internal tubes.
- Have rings within them to strengthen the tubes and keep them open.
What are the tracheoles in insects?
- Trachea branch into smaller tubes, deeper into the abdomen of the insect.
- These extend throughout all the tissues in the insect to deliver oxygen to all respiring cells.
What are the 3 methods of moving gases into the tracheal system?
- Gases can exchange via simple diffusion.
- Gas can exchange by mass transport.
- Anaerobic respiration.
How can gases exchange via simple diffusion?
- When cells respire, they use up oxygen and produce carbon dioxide.
- Creating a concentration gradient from the tracheoles to the atmosphere.
- Meaning O2 moves in via diffusion.
How can gases exchange via mass transport?
- Insects contract and relax their abdominal muscles to pump and move gases on mass.
- In and out of the tracheal system.
How can gases exchange via anaerobic respiration?
- When the insect is in flight, the muscle cells start to respire anaerobically, producing lactate.
- This lowers the water potential of the cells, meaning water moves from the tracheoles into the cells via osmosis.
- This decreases the volume in the tracheoles.
- As a result, more air from the atmosphere is drawn in.
What are the adaptations of insects for efficient diffusion - surface area?
- Large number of tracheoles.
- Large surface area.
What are the adaptations of insects for efficient diffusion - diffusion distance?
- Walls of tracheoles are thin.
- There is a short distance between spiracles and tracheoles.
- Means there is a short diffusion distance.
What are the adaptations of insects for efficient diffusion - concentration gradient?
- Use of oxygen in respiring cells + production of carbon dioxide.
- Maintains a steep diffusion distance.
Where does most photosynthesis occur in a leaf?
Palisade mesophyll.
What diffuses OUT of the stomata?
Oxygen and water vapour.
What diffuses IN at the stomata?
Carbon dioxide.
Why do the stomata close at night?
To reduce water loss via evaporation -> as photosynthesis doesn’t happen at night.
When do guard cells open (to form the stomata)?
When they are swollen.
What are xerophytic plants adapted to do?
Survive in environments with limited water.
What is the balance that plants have to achieve?
Requiring CO2 for photosynthesis AND not losing essential water via evaporation.
What adaptations do xerophytes have to enable efficient gas exchange, whilst also limiting water loss?
- Curled leaves.
- Hairs.
- Sunken stomata.
- Thicker waxy cuticle.
- Longer root network.
How do curled leaves on xerophytes enable efficient gas exchange, whilst also limiting water loss?
- Trap moisture that is evaporating.
- Meaning humidity increases.
- Which reduces the water potential gradient from the inside of the plant to the outside.
- Which reduces further evaporation.
How do hairs on xerophytes enable efficient gas exchange, whilst also limiting water loss?
- Stick out and trap water that is evaporating out of the leaf.
- Which traps water, increasing the humidity.
- Which decreases the water potential gradient.
- Meaning less evaporation/transpiration occurs.
How do sunken stomata on xerophytes enable efficient gas exchange, whilst also limiting water loss?
- Traps moisture.
- Increases humidity.
- Decreases water potential gradient.
- Meaning less evaporation occurs.
How does the thicker waxy cuticle on xerophytes enable efficient gas exchange, whilst also limiting water loss?
Reduces evaporation.
