3.2 Gas Exchange Flashcards
Describe the process of inhalation in humans
- Diaphragm contracts and flattens
- External intercostal muscles contract, and internal intercostal muscles relax
- Ribcage pulled up and out
- So volume of thorax increases
- So pressure in thorax decreases
- Pressure in thorax lower than atmospheric, so air moves into lungs down the pressure gradient
What are the three most key important features of an efficient gas exchange system
- Large surface area
- Short diffusion distance / pathway
- Concentration gradient maintained
Describe the process of exhalation in humans
- Diaphragm relaxes and domes
- External intercostal muscles relax, and internal intercostal muscles contract
- Ribcage pulled in and down
- So volume in thorax decreases
- So pressure in thorax increases
- As pressure in thorax is greater than in atmosphere, air moves down pressure gradient out of lungs
Pulmonary ventialation rate equation
PVR = tidal volume x breathing rate
Tidal volume equation
PVR / breathing rate
Breating rate equation
PVR / tidal volume
Points to assess if data is reliable
- Large sample size
- Individuals chosen at random
- Individuals healthy
- Equal number of males and females / same sex
- Repeat readings
Points to challenge assumptions made with data
- Influence of other factors
- Further studies required
- How great is the difference / data
Explain how the human gas exhange system is specialised - for large surface area
Large number of alveoli
Explain how the human gas exhange system is specialised - for short diffusion distance/pathway
- Alveoli epithelium cell is one flattened cell thick
- Capillary walls are one flattened cell thick
Explain how the human gas exhange system is specialised - for maintaining high concentration gradient
- Constant flow of blood through capillary network
- Ventilation in lungs replenishes air
How are single celled organisims speciallised for gas exchange
- Cells are flattened and long, so large surface area and reduced diffusion distance/pathway
- Oxygen quickly used in respiration so maintains a high concentration gradient
Explain how the fish gas exhange system is specialised - for large surface area
- Large number of gill fillaments and lamellae
Explain how the fish gas exhange system is specialised - for short diffusion distance/pathway
- Lamellae are thin
- Many capillaries in the lamellae
Explain how the fish gas exhange system is specialised - for concentration gradient maintained
Counter-current mechanism
Explain the counter-current mechanism
- Blood and water flow in opposite directions
- Blood always passes water with higher oxygen concentration
- Oxygen diffusion gradient maintained across entire length of gill
- So diffusion occurs across entire length of gill
Explain how the insect gas exhange system is specialised - for large surface area
Tracheoles are highly branched
Explain how the insect gas exhange system is specialised - for short diffusion distance/pathway
- Tracheoles are highly branched
- Tracheole walls are thin and permeable to oxygen
- Many spiraces
Describe the movement of oxygen in insect gas exhange systems
Spiracles open to allow oxygen to move by diffusion down diffusion gradient which then lead to trachea to traceoles to cells
Describe adaptations to insect gas exchange system when anaerobically respiring
Water moves out of tracheoles, reducing diffusion distance of oxygen in water
Describe abdominal pumping
- Only occurs when CO2 concentration very high
- Pumping raises pressure in body
- So carbon dioxide moves out down pressure gradient into atmosphere
How is the insect gas exhange system adapted to prevent water loss
- Chitin exoskeleton is impermeable
- Spiracles close during inactivity
- Spiracle surrounded by hairs which traps a layer of air saturated with water, decreasing concentation gradient
How are plants specialised to maximise gas exchange
- Large surface area of leaves, so greater number of stomata
- Many stomata, so short diffusion distance to/from spongy mesophyll cells
- Thin leaves, so short diffusion distance to/from spongy mesophyll cells
- Carbon dioxide quickly used in photosythesis to maintain high concentration gradient
How are plants specialised to reduce water loss
- Thicker waxy cuticle to increase diffusion distance of water, and so reduce evaportation of water
- Atomata in pits
- Stomata surrounded by hairs
- Leaves are rolled
- All trap water and decrease the water potential gradient
- Leaves are spines so reduces the SA:V ratio
