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Biology 🧬 > 3.2 Gas exchange > Flashcards

3.2 Gas exchange Flashcards

1
Q

Name three features of an efficient gas exchange surface

A
  1. Large surface area, e.g. folded membranes in mitochondria
  2. Short distance, e.g. wall of capillaries
  3. Steep concentration gradient, maintained by blood supply or ventilation, e.g. alveoli
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2
Q

Why can’t insects use their bodies as an exchange surface?

A

They have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water

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3
Q

Name the three main features of an insect’s gas exchange

A
  • Spiracles
  • Tracheae
  • Tracheoles
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4
Q

Describe spiracles

A

Holes on the body’s surface which may be opened or closed by a valve for gas or water exchange

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5
Q

Describe tracheae

A

Large tubes extending through all body tissues, supported by rings to prevent collapse

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6
Q

Describe tracheoles

A

Smaller branches dividing off the tracheae

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7
Q

Explain the process of gas exchange in insects

A
  • Gases move in and out of tracheae through the spiracles
  • A diffusion gradient allows oxygen to diffuse into the body tissue while waste carbon dioxide diffuses out
  • Contraction of muscles in the tracheae allows mass movement of air in and out
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8
Q

Why can’t fish use their bodies as an exchange surface?

A

They have a waterproof, impermeable outer membrane and a small surface area to volume ratio

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9
Q

Name the two main features of a fish’s gas transport system

A
  • Gills
  • Lamellae
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10
Q

Describe gills

A

Located within the body, supported by arches, along which are multiple projections of gill filaments, which are stacked up in piles

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11
Q

Describe lamellae

A

At right angles to the gill filaments, they give an increased surface area. Blood and water flow across them in opposite directions (countercurrent exchange system)

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12
Q

Explain the process of gas exchange in fish

A
  • The fish opens its mouth, lowering the buccal cavity, which enables water to flow in
  • Then the fish closes its mouth, causing the buccal cavity to raise, increasing the pressure
  • The water passes over the lamellae. and the oxygen diffuses into the bloodstream
  • Waste carbon dioxide diffuses into the water and flows back out the gills
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13
Q

Describe the countercurrent exchange system

A

Blood and water flow in opposite directions to each other across the lamellae

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14
Q

How does the countercurrent exchange system maximise oxygen absorbed by the fish?

A

Maintains a steep concentration gradient, as water is always next to blood of a lower oxygen concentration. Keeps rate of diffusion constant and enables 80% of available oxygen to be absorbed

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15
Q

Name three adaptations of a leaf that allows efficient gas exchange

A
  • Thin and flat
  • Stomata
  • Air spaces
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16
Q

Describe how a thin and flat leaf allows efficient gas exchange

A

Thin and flat to provide short diffusion pathway and large surface area to volume ratio

17
Q

Describe how stomata allows efficient gas exchange

A

Many minute pores in the underside of the leaf (stomata) allow gases to easily enter

18
Q

Describe how air spaces allows efficient gas exchange

A

Air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis

19
Q

How do plants limit their water loss while still allowing gases to be exchanged?

A

Stomata regulated by guard cells which allows them to open and close as needed. Most stay closed to prevent water loss while some open to let oxygen in

20
Q

Describe the pathway taken by air as it enters the mammalian gaseous exchange system

A
  • Nasal cavity
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
21
Q

Describe the function of the nasal cavity in the mammalian gaseous exchange system

A

A good blood supply warms and moistens the air entering the lungs. Goblet cells in the membrane secrete mucus which traps dust and bacteria

22
Q

Describe the trachea and its function in the mammalian gaseous exchange system

A
  • Wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes
  • Lined by ciliated epithelium cells which move mucus towards the throat to be swallowed, preventing lung infections
  • Carries air to the bronchi
23
Q

Describe the bronchi and their function in the mammalian gaseous exchange

A
  • Like the trachea they are supported by rings of cartilage and are lined by ciliated epithelium cells
  • However, they are narrower and there are two
  • Allow passage of air into the bronchioles
24
Q

Describe the bronchioles and their function in the mammalian gaseous exchange system

A
  • Narrower than the bronchi
  • Don’t need to be kept open by cartilage, therefore mostly have only muscle and elastic fibred so that they can contract and relax during ventilation
  • Allow passage of air into the alveoli
25
Q

Describe the alveoli and their function in the mammalian gaseous exchange system

A
  • Mini air sacs, lined with epithelium cells, site of gas exchange
  • Walls only one cell thick, covered with a network of capillaries, 300 million in each lung, all of which facilitates gas diffusion
26
Q

Describe ventilation

A

Ventilation is the flow of air in and out of the alveoli; it is composed of two stages: inspiration and expiration

27
Q

How does ventilation occur?

A

Ventilation occurs with the help of two sets of muscles, the intercostal muscles and the diaphragm

28
Q

Explain the process of inspiration and the changes that occur throughout the thorax

A
  • External intercostal muscles contract (while internal relax), pulling the ribs up and out
  • Diaphragm contracts and flattens
  • Volume of the thorax increases
  • Air pressure outside the lungs is therefore higher than the air pressure inside, so air moves in
29
Q

Explain the process of expiration and the changes that occur throughout the thorax

A
  • External intercostal muscles relax (while internal relax), bringing the ribs down and in
  • Diaphragm relaxes and domes upwards
  • Volume of the thorax decreases
  • Air pressure inside the lungs is therefore higher than the air pressure outside, so air moves out
30
Q

What is tidal volume?

A

The volume of air we breathe in and out during each breath at rest

31
Q

What is breathing rate?

A

The number of breaths we take per minute

32
Q

How do you calculate pulmonary ventilation rate?

A

Tidal volume x breathing rate
These can be measured using a spirometer, a device which records volume changes onto a graph as a person breathes

33
Q

What is vital capacity?

A

The maximum volume of air that can be inhaled or exhaled in a single breath

34
Q

What is residual volume?

A

The volume of air in which is always present in the lungs

Biology 🧬 (38 decks)

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