OESWTE: Gas exchange Flashcards
What three features of the human lungs maximise the rate of diffusion:
- Short diffusion pathway
- Large surface area
- Steep concentration gradient of oxygen and carbon dioxide
Explain the factor of short diffusion pathway:
- The alveolar epithelium is one cell thick
- Gases have a short diffusion distance so gas exchange is quick and efficient.
Explain the factor of large surface area:
- The large number of alveoli increases the surface area available for oxygen and carbon dioxide to diffuse across.
Explain the factor of steep concentration gradient of oxygen and carbon dioxide:
- The constant ventilation and flow of blood
- Oxygenated blood is brought away from the alveoli and deoxygenated blood is brought to them.
- Maintains concentration gradient needed for gas exchange
Explain inhalation during exercise in the human lungs:
- Diaphragm contracts
- External intercostal muscles contract
- Thorax volume increases, pressure decreases
- Air is forced into the lungs
Explain exhalation during exercise in the human lungs:
- Diaphragm relaxes
- Internal intercostal muscles contract
- Thorax volume decreases, pressure increases
- Air is forced out of the lungs
What two ways are the gills in fish adapted for gas exchange?
- Steep concentration gradient of oxygen and carbon dioxide
- Large surface area
Explain the fish adaptation of steep concentration of oxygen and carbon dioxide:
- The countercurrent flow in the lamellae allows a steep concentration gradient to be maintained so oxygen moves into the the blood along the entire length of the gill
Explain the fish adaptation of large surface area:
- The gills have gill fillaments which have lamellae
Why is the countercurrent flow in fish an advantage?
- Means equilibrium is never reached
- Diffusion gradient will always be maintained along the entire length of the gill
- Constant flow of oxygen
Single celled organisms absorb and release gases by diffusion through their ___________.
Cell-surface membranes
Fish have a _________ system of blood flow.
Counter-current
What happens in the counter-current system in fish?
Blood flows through the lamellae in one direction
Water flows over the lamellae in the opposite direction.
What is the purpose of the counter-current system in fish?
Water with a high oxygen concentration always flows next to blood with a lower oxygen concentration - steep concentration gradient is maintained between water and blood.
What is the main gas exchange surface in plants?
Mesophyll cells
In plants what are the pores called which gases move in and out of?
Stomata
What cells control the opening and closing of the stomata?
Guard cells
Why do insects have an exoskeleton?
- Protection
- Prevent water loss (with lipid layer)
What do insects have instead of lungs?
Tracheal system
What are spiracles?
- Round, valve-like openings along the abdomen of an insect
What substances enter and leave via spiracles?
- Oxygen
- Carbon Dioxide
What is the trachea?
A network of internal tubes
In an insects tracheal system, what is the purpose of trachea tubes having rings?
- Strength the tubes
- Keep the tubes open
Explain the anatomy of an insects tracheal system:
Spiracles (holes) along the insects abdomen.
Trachea attach to spiracles.
Trachea branches into tracheoles.
What is the role of the tracheoles in an insects tracheal system?
Deliver oxygen to respiring cells.
What are the three methods of moving gases into the tracheal system in insects?
1) Diffusion
2) Mass transport
3) Anaerobic respiration
Explain diffusion as a method of moving gases into the tracheal system in insects:
- Respiring cells use up oxygen and produce carbon dioxide
- Concentration gradient from the tracheoles to the atmosphere
Explain mass transport as a method of moving gases into the tracheal system in insects:
- Insects abdominal muscles contract and relax
Explain anaerobic respiration as a method of moving gases into the tracheal system in insects:
- When insects are in flight their cells respire anaerobically to produce lactate.
- Lactate lowers water potential of the cells, so water moves from the tracheoles into the cells (osmosis)
- Decreases volume of the tracheoles so more air is drawn in.
Give the three insect adaptations to prevent water loss:
- Small surface area:volume ratio for water to evaporate from
- Waterproof exoskeleton
- Spiracles can open and close
When a plant has sufficient water it enters the guard cell making them turgid. This _____ the stomatal pore.
Opens
If a plant is dehydrated the guard cells become flaccid. This _____ the stomatal pore.
Closes
Give the 5 adaptations of xerophytes:
1) Stomata are sunk in pits to trap water vapour (reduces evaporation)
2) Layer of hairs on the epidermis to trap water around the stomata
3) Stomata is inside curled leaves (protects them from wind)
4) Reduced number of stomata
5) Thick, waxy, waterproof cuticle
Give an example of an area with a low partial pressure:
Respiring tissues
Give an example of an area with a high partial pressure:
Alveoli
What happens to oxygens in areas of low partial pressure?
Oxygen is offloaded
What happens to oxygen in areas with a high partial pressure?
Oxygen is loaded
What is the advantage of the alveolus’ walls containing the protein elastin?
Helps the alveoli return to their normal shape after inhaling and exhaling air.
What are the three adaptations of the alveoli that increase the rate of diffusion?
- Alveolar epithelium is only one cell thick (short diffusion pathway)
- Large surface area for gas exchange
- Good blood supply (allows steep concentration of oxygen and carbon dioxide)
Define tidal volume:
The volume of air in each breath.
Define ventilation rate:
The number of breaths per minute.
What is tuberculosis caused by?
Bacteria
Explain the impact of tuberculosis on the lungs:
- Immune system cells build a wall around the bacteria in the walls
- Small, hard lumps are formed (tubercles)
- Infected tissue dies, so the surface for gas exchange is damaged
- Tidal volume is decreased
What is the impact of a reduced tidal volume?
Less air can be inhaled with each breath
What is fibrosis?
The formation of scar tissue in the lungs.
What causes fibrosis?
Exposure to harmful substances e.g. asbestos, dust
Explain the impact of fibrosis on the lungs:
- Scar tissue is thicker and less elastic than healthy tissue
- Lungs are less able to expand and so cant hold as much air as normal
- Tidal volume and FVC is reduced
Define FVC:
Forced vital capacity - The maximum volume of air it is possible to breathe out after a deep breath in.
What is asthma?
Condition where the airways become inflamed and irritated.
What causes asthma?
- Environmental factors e.g. pollen, dust
- Genetics
What happens during an asthma attack?
- Smooth muscles contract
- Large amounts of mucus are produced
- Airways are significantly constricted
- FEV is reduced
Define FEV:
Forced expiratory volume - The maximum volume of air that can be breathed out in 1 second.
What is emphysema caused by?
Smoking or long-term exposure to air pollution.
Explain how the lungs are impacted by emphysema:
- Foreign particles become trapped in the alveoli causing inflammation
- Phagocytes come to the inflamed area and produce a protein that breaks down elastin
- Loss of elastin means alveoli cant recoil air as well and destroys the alveoli walls
Insect trachae provide tubes of air. How does this increase the efficiency of gas exchange?
Means gases can diffuse quickly into tissues.
