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A-LEVEL BIOLOGY > 3.2 Gas Exchange > Flashcards

3.2 Gas Exchange Flashcards

1
Q

Describe the process of inhalation in humans

A
  • Diaphragm contracts and flattens
  • External intercostal muscles contract, and internal intercostal muscles relax
  • Ribcage moves 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
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1
Q

What are the three most key important features of an efficient gas exchange system

A
  • Large surface area
  • Short diffusion distance / pathway
  • Concentration gradient maintained
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2
Q

Describe the process of exhalation in humans

A
  • Diaphragm relaxes and domes
  • External intercostal muscles relax, and internal intercostal muscles contract
  • Ribcage moves 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
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3
Q

Pulmonary ventialation rate equation

A

PVR = tidal volume x breathing rate

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4
Q

Tidal volume equation

A

PVR / breathing rate

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5
Q

Breating rate equation

A

PVR / tidal volume

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6
Q

Points to assess if data is reliable

A
  • Large sample size
  • Individuals chosen at random
  • Individuals healthy
  • Equal number of males and females / same sex
  • Repeat readings
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7
Q

Points to challenge assumptions made with data

A
  • Influence of other factors
  • Further studies required
  • How great is the difference / data
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8
Q

Explain how the human gas exhange system is specialised - for large surface area

A

Large number of alveoli

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9
Q

Explain how the human gas exhange system is specialised - for short diffusion distance/pathway

A
  • Alveoli epithelium cell is one flattened cell thick
  • Capillary walls are one flattened cell thick
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10
Q

Explain how the human gas exhange system is specialised - for maintaining high concentration gradient

A
  • Constant flow of blood through capillary network
  • Ventilation in lungs replenishes air
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11
Q

How are single celled organisims speciallised for gas exchange

A
  • 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
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12
Q

Explain how the fish gas exhange system is specialised - for large surface area

A
  • Large number of gill fillaments and lamellae
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13
Q

Explain how the fish gas exhange system is specialised - for short diffusion distance/pathway

A
  • Lamellae are thin
  • Many capillaries in the lamellae
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14
Q

Explain how the fish gas exhange system is specialised - for concentration gradient maintained

A

Counter-current mechanism

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15
Q

Explain the counter-current mechanism

A
  • 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
16
Q

Explain how the insect gas exhange system is specialised - for large surface area

A

Tracheoles are highly branched

17
Q

Explain how the insect gas exhange system is specialised - for short diffusion distance/pathway

A
  • Tracheoles are highly branched
  • Tracheole walls are thin and permeable to oxygen
  • Many spiraces
18
Q

Describe the movement of oxygen in insect gas exhange systems

A

Spiracles open to allow oxygen to move by diffusion down diffusion gradient which then lead to trachea to traceoles to cells

19
Q

Describe adaptations to insect gas exchange system when anaerobically respiring

A

Water moves out of tracheoles, reducing diffusion distance of oxygen in water

20
Q

Describe abdominal pumping

A
  • Only occurs when CO2 concentration very high
  • Pumping raises pressure in body
  • So carbon dioxide moves out down pressure gradient into atmosphere
21
Q

How is the insect gas exhange system adapted to prevent water loss

A
  • Chitin exoskeleton is impermeable
  • Spiracles close during inactivity
  • Spiracle surrounded by hairs which traps a layer of air saturated with water, decreasing concentation gradient
22
Q

How are plants specialised to maximise gas exchange

A
  • 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
23
Q

How are plants specialised to reduce water loss

A
  • 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

A-LEVEL BIOLOGY (25 decks)

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