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1B > CGP Gas Exchange > Flashcards

CGP Gas Exchange Flashcards

1
Q

3 examples of when organisms need to exchange substances with their environment?

A
  • oxygen for aerobic respiration
  • excrete waste products eg urea and carbon dioxide
  • heat (in order to remain at same temperature)
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2
Q

What kind of SA:V ratio do small animals have?

A

Large SA:V ratio.

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3
Q

Unlike single called organisms, why is diffusion across the outer membrane in multicellular organisms too slow?

A
  • some cells are deep within the body; a big distance between them and the outside environment.
  • larger animals have a small SA:V ratio; difficult to exchange substances for a large volume of animal from a small SA.
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4
Q

Most gas exchange systems have two things in common…

A
  • large SA

- they’re thin (just one layer of epithelial cells); providing a short diffusion pathway across gas exchange pathway

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5
Q

What system do fish use for gas exchange?

A

Counter current system

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6
Q

Why do fish need to use a counter current system?

A

Because there’s a lower concentration of oxygen in water than in air.

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7
Q

Outline how the counter current system works in fish.

A
  1. Water enters the mouth, then through the gills (each of which is made of gill filaments, providing a large SA for gas exchange).
  2. The gill filaments also have lamellae, further increasing SA.
  3. Blood flows through the lamellae in one direction and water flows in the opposite direction. This maintains a large conc. gradient between the water and blood.
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8
Q

What do insects use for gas exchange?

A

Tracheae

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9
Q

What adaptations do the lamellae in fish have for gas exchange?

A

They increase the SA (as they are tiny structures on full filaments).
They also have lots of blood capillaries and a thin surface layer of cells to speed up the rate of diffusion.

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10
Q

Outline gas exchange in the tracheae in insects.

A
  1. Air moves into the tracheae through spiracles (pores on the surface).
  2. Oxygen travels down the conc. gradient towards the cells.
  3. Tracheae break down into smaller tracheoles and go into individual cells. This means oxygen diffuses directly into respiring cells
  4. CO2 from the cells moves down its own conc. gradient towards the spiracles to be released into the atmosphere.
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11
Q

What are tracheae?

A

Microscopic air filled pipes used by insects for gas exchange.

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12
Q

Where do dicotyledonous plants do gas exchange?

A

At the surface of mesophyll cells.

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13
Q

How are mesophyll cells adapted to their function of gas exchange?

A

They have a large SA.

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14
Q

In mesophyll cells, gases move in and out of…

A

Pores in the epidermis called stomata.

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15
Q

Stomata open to…

A

Allow the exchange of gases.

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16
Q

Stomata close to…

A

Prevent the plant from losing too much water.

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17
Q

What do guard cells do?

A

Control the opening and closing of stomata.

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18
Q

Gas exchange causes water loss. But how do insects avoid losing too much water?

A

If insects are losing too much water, they close their spiracles using muscles.

They also have a waterproof, waxy cuticle all over their body and tiny hairs, both of which reduce evaporation.

19
Q

Gas exchange causes water loss. But how do plants prevent too much water loss?

A

Plant’s stomata are kept open during the day to allow gas exchange. Water enters guard cells, making them turgid and opening the stomatal pore. If the plant starts to get dehydrated, the guard cells lose water and become flaccid, which closes the pore.

20
Q

What are xerophytes?

A

Plants that are specially adapted for warm, dry or windy habitats where water is a problem.

21
Q

Give examples of some xerophytic adaptations.

A
  • reduced number of stomata to reduce water loss
  • a layer of hairs on epidermis, to trap moist air round the stomata
  • waxy, waterproof cuticles on leaves and stem to reduce evaporation
  • curled leaves with stomata inside, protecting them from wind (as windy conditions increase the rate of diffusion and evaporation)
22
Q

As you breathe in, air enters the _________.

A

Trachea (windpipe).

23
Q

The trachea splits into 2 _________.

A

Bronchi.

One broncos then leads to each lung.

24
Q

Each broncus then branches off into smaller tubes aka _____________.

A

Bronchioles.

25
Q

The bronchioles end in _____________. This is where gases are exchanged.

A

Alveoli.

26
Q

What are the layers of intercostal muscles?

A

Internal and external intercostal muscles.

27
Q

What is ventilation?

A

Ventilation consists of inspiration (breathing in) and expiration (breathing out).
It’s controlled by movements of the diaphragm, internal and external intercostal muscles and rib cage.

28
Q

Outline the process of inspiration.

A
  1. The external intercostal muscles and diaphragm contract.
  2. This causes the rib cage to move upwards and outwards. And the diaphragm to flatten, increasing the volume of the thoracic cavity (the space where the lungs are).
  3. As the volume of the thoracic capacity increases, the lung pressure decreases to below atmospheric pressure.
  4. Air flows from an area of higher pressure to an area of lower pressure, so air flows from the trachea into the lungs.
29
Q

Inspiration is a(n) ________ process.

A

Active

30
Q

Outline the process of exhalation.

A
  1. The external intercostal and diaphragm relax.
  2. The rib cage moves downwards and inwards, and the diaphragm becomes curved again.
  3. The volume of the thoracic capacity decreases, causing the air pressure to decrease (to above atmospheric pressure).
  4. Air is forced down the conc. gradient, and out of the lungs.
31
Q

Exhalation is a(n) _________ process.

Does it require energy?

A

A passive process. It doesn’t require energy.

32
Q

In what way does forced exhalation use antagonistic pairs?

A

Because during forced exhalation, the external intercostal muscles relax, and internal intercostal muscles contract, piling the rib cage further down and in.

During this, the 2 sets of intercostal muscles are antagonistic (opposing).

33
Q

In humans, gaseous exchange occurs in the…

A

Alveoli.

34
Q

In what way are the alveoli adapted for gas exchange?

A
  • they have a thin exchange surface. The alveolar epithelium is only one cell thick; meaning a short diffusion pathway.
  • large SA. The large number of alveoli means there’s a large SA for gas exchange.
  • steep conc. gradient of O2 and CO2 between the alveoli and capillaries (which increases rate of diffusion). This is maintained by constant flow of blood and ventilation.
35
Q

Alveoli are surrounded by a network of ____________.

A

Capillaries

36
Q

How does oxygen get into the blood?

A

Oxygen moves down the trachea, bronchi and bronchioles into the alveoli, down the pressure gradient.

Oxygen then diffuses out of the alveoli, across the alveolar epithelium and capillary epithelium, and into haemoglobin in the blood.

37
Q

How does CO2 leave the body?

A

CO2 diffuses into the alveoli from the blood and is breathed out.

38
Q

Define tidal volume.

A

The volume of air in each breath.

Usually between 0.4 and 0.5dm3 for adults.

39
Q

Define ventilation rate.

A

The number of breaths per minute.

40
Q

Define forced exploratory volume.

A

The maximum volume of air that can be breathed out in 1 second.

41
Q

Define forced vital capacity.

A

The maximum volume of air it’s possible to breathe forcefully out of the lungs after a deep breath in.

42
Q

What is a spirometer?

A

A machine used to measure the volume of air breathed in and out. Can be used to find out tidal volume, ventilation rate etc.

43
Q

Define risk factor.

A

Factors that increase the chance of a person getting that disease

44
Q

What is the issue with dissecting animals to investigate gas exchange?

A
  • morally wrong to kill animals just for dissections; unnecessary killing. However, many dissections are of animals which have already been killed for their meat.
  • animals used for dissection not always treated in a humane way; they may be subject to overcrowding / extreme temperatures / lack of food. And they may not be killed humanely either.

1B (35 decks)

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