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A Level Biology > Gas Exchange > Flashcards

Gas Exchange Flashcards

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1
Q

Adaptations of gas exchange

A

Large surface area

Thin so short diffusion pathway across the gas exchange surface.

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2
Q

How do single called organisms exchange gases

A

Across their body surface.

They absorb and release gases by diffusion through outer surface.

They have a relatively large surface area, thin surface and short diffusion pathway so there’s no need for a gas exchange system as O2 can take part in a biochemical reaction soon as it diffuses.

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3
Q

Gas exchange in fish

A
  1. Fish use a counter current system for gas exchange.
  2. Lower concentration of oxygen in water than air so fish have special adaptations.
  3. Water containing oxygen enters mouth and passes out of gills.
  4. Each gill made of lots of thin plates called gill filaments and so have a large surface area for gas exchange.
  5. Gill filaments are covered in tiny structures called lamellae which increase the surface area.
  6. Lamellae has lots of blood capillaries and thin surface layer of cells.
  7. Blood flows through lamellae in one direction and water flows in the opposite direction - counter current system.
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4
Q

Counter current system

A

Maintains a large concentration gradient between water and the blood. Oxygen concentration in water is always higher than in the blood, so as much oxygen as possible diffuses from water into blood.

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5
Q

How does deoxygenated blood turn into oxygenated in fish

A

Flows in each gill arch, down inner side of each filament, across gill lamella and back. So it then becomes oxygenated.

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6
Q

What happens to filaments when not wet

A

They stick together sí surface area becomes too small for efficient gas exchange

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7
Q

Where do the gills lie

A

In a cavity in the pharynx between buccal cavity and oesophagus which is surrounded by a movable operculum.

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8
Q

Describe and explain how counter current system leads to efficient gas exchange across gills?

A
  1. Water and blood flow in opposite directions.
  2. Maintains concentration gradient a long while length of gill.
  3. Water has a higher concentration of oxygen than the blood that flows next to it.
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9
Q

Which is a thicker lamellae not efficient

A

Longer diffusion distance do not efficient

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10
Q

Why is a lamellae not efficient when it fuses

A

Surface area is reduced.

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11
Q

Why is the direction of water and blood flow useful to a fish?

A

It has a concentration gradient maintained and more oxygen in the blood. More aerobic respiration to release energy for muscle contraction.

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12
Q

Gill lamellae

A

The folds are kept supported and moist by the water that is continually pumped through the mouth and over the gills

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13
Q

What do fish have that’s efficient in the lamellae

A

Fish also have an efficient transport system within the lamellae which maintains the concentration gradient across the lamellae.

Counter current system.

The arrangement of water flowing past the gills in the opposite direction to the blood (called countercurrent flow) means that they can extract oxygen at 3 times the rate a human can.

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14
Q

Counter current system

A

As the blood flows in the opposite direction to the water, it always flows next to water that has given up less of its oxygen.

This way, the blood is absorbing more and more oxygen as it moves along. Even as the blood reaches the end of the lamella and is 80% or so saturated with oxygen, it is flowing past water which is at the beginning of the lamella and is 90 or 100% saturated.

Therefore, even when the blood is highly saturated, having flowed past most of the length of the lamellae, there is still a concentration gradient and it can continue to absorb oxygen from the water.

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15
Q

Why is counter current system an advantage

A

Allows maximum oxygen to be absorbed by the blood from the water, by maintaining the concentration gradient the whole way through the gills.

This means fish can get enough oxygen without having to push large amounts of water through their gills, which would require a lot of energy, so the counter-current system is a more efficient way of increasing the amount of oxygen diffusing into the blood.

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16
Q

Problem with insects

A

They lose water very easily through their body surface.

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17
Q

Gas exchange in insects

A
  1. Insects have microscopic air filled pipes called tracheae which they use in gas exchange.
  2. Air moves into trachea thru spirackes
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18
Q

What does insects use to move air in and out of spiracles

A

Rhythmic abdominal movements.

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19
Q

What gives a large surface area in insects

A

Tracheae and tracheoles.

Tracheole lined with single layer of cells to minimise diffusion distance.

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20
Q

For efficient gas exchange

A
  1. Thin permeable surface over large areas

2. Balance the need of exchanging materials

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21
Q

How do u reduce water loss

A
  1. Water proof covering.
  2. Small surface area: volume.
  3. Close spiracles using muscles and tiny hairs around it - reduces evaporation
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22
Q

Insects structure

A
  1. Tracheae. Supported by cartilage to prevent collapse.
  2. Tubes branch to tra helped and extend throughout its body therefore oxygen can be delivered direct to respiring tissues.
  3. Movement of oxygen/ air along trachea is due to diffusion gradient and muscles in the insect contracting.
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23
Q

How does oxygen move into gas exchange system when insect at rest

A

Due to concentration gradient. The concentration gradient maintained because the tracheoles dip into the respiring tissue.

Oxygen used in respiration and establish a concentration gradient so oxygen diffuses in.

Oxygen diffused into respiring cells and tissues from tracheae.

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24
Q

Which plants exchange gases at the surface of the mesophyll cells

A

Dicotyledonous plants

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25
Q

What’s the waste gas produced when plants use CO2 for photosynthesis

What about when its respiration

A

Oxygen

Co2

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26
Q

What’s the main gas exchange surface in plants

How are they well adapted

A

Surface of the mesophyll cells in the leaf. They’re well adapted for their function as they have a large surface area

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27
Q

What do you gases move in and out of

A

Special pores in the epidermis called stomata

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28
Q

What does the stomata do

A

Opens to allow gas exchange and close if there is too much water loss

29
Q

What controls the opening and closing of the stomata

A

Guard cells

30
Q

How do plants reduce water loss

A

Stomata kept open during the day to allow gas exchange. Water enters guard cells making them turgid and that opens the stomatal pore.

Guard cells close if plants get dehydrated and become flaccid.

xerophytes are adapted to warm dry and windy conditions

31
Q

Adaptations of an xerophytic

A

Stomata sunk in pits. Trap moist air and reduce conc. gradient of water between leaf and air. So that reduces water diffusing out of the leaf and evaporating away.

Hairs trap moist air around the stomata.

Curled leaves with stomata inside, protecting them from wind. Wind increase rate of diffusion and evaporation.

Reduced number of stomata so fewer places for water to evaporate from.

Wavy waterproof cuticles on leaves and stems to reduce evaporation.

32
Q

Plants similar to insects as

A

No. Of cells far from external air.

Diffusion takes place in air.

33
Q

Why might the rate of water uptake not be the same as rate of transpiration

A
  1. Used in photosynthesis

2. Used for support

34
Q

What are lungs

A

Specialised organs for gas exchange.

35
Q

What do humans need in their body

A

Oxygen in the blood And to get rid of co2 made by respiring cells.

36
Q

Use of gas exchange system in humans

A

Remove co2 and put oxygen in blood

37
Q

Order of human gas exchange system

A
  1. Trachea
  2. Bronchus / Bronchi
  3. Bronchioles
  4. Alveoli
  5. Intercostal muscles and external
  6. Rib cage
  7. Lungs
  8. Diaphragm
  9. Thorax
  10. Abdomen
38
Q

Trachea

A

Flexible airway supported by cartilages so don’t collapse. Walls made of muscles and lined with ciliates epithelium and globlet cells.

39
Q

Bronchi

A

Two divisions of trachea. Lead to each lung supported by cartilage and contain muscles. Produce mucus

40
Q

Bronchioles

A

Series of branching tubes. Muscle walls with epithelium cells lined across it.

41
Q

Alveoli

A

Minute air sacs - gas exchange and end of bronchioles. Made of epithelial and elastic so stretch when fill with air and spring back when breathe out.

42
Q

Ribcage

A

Support and protect lungs

43
Q

Volume of o2 required and volume of co2 needed to be removed is high in mammals because

A

Large no. Of cells

Maintain high body temp so high metabolic and respiratory rates

44
Q

Why are lungs inside body

A

Would lose water and dry outside the body

Air not dense enough to support and protect delicate structure

45
Q

Pulmonary ventilation

A

Total vol. of air taken into lungs in a given time

PV (dm3/min) = TV (dm3) x VR (per min)

TV usually 0.5
VR no. Of breathes in a min.

46
Q

What is ventilation

A

Breathing in and out.

Inspiration and expiration.

47
Q

What is ventilation controlled by

A

Diaphragm, internal and external intercostal muscles and ribcage.

48
Q

Inspiration

A
  1. External intercostal and diaphragm muscles contract.
  2. Rib cage up and out
  3. Diaphragm muscle flat and down
  4. Volume of thorax increases
  5. Pressure inside decreases
  6. Air drawn in (air flows from high pressure to low down trachea and into lungs) down the pressure gradient
  7. Inspiration is an active process and requires energy
49
Q

Expiration

A
  1. External intercostal and diaphragm muscles relax.
  2. Ribcage down and in
  3. Diaphragm curved and up
  4. Volume in thorax decreases
  5. Pressure increases
  6. Air forced down pressure gradient and out of lungs.
  7. Normal expiration is a passive process and doesn’t require energy. It can be forced though where he external intercostal muscle relaxes and the internal intercostal muscles contract
50
Q

Antagonistic

A

Opposing intercostal muscles during time of expiration being forced.

51
Q

Where does gaseous exchange happen in humans

A

In the alveoli

52
Q

Alveoli

A

Air sacs where gas exchange occurs in lungs.

53
Q

What is each alveoli made up from

A

single layer of thin, flat cells called alveolar epithelium

54
Q

Adaptations of alveoli

A
  1. Huge No. of Alveoli in lungs so big surface area for oxygen and carbon dioxide exchange.
  2. Large surface area: volume ratio so speeds up gas exchange
  3. Short diffusion pathway one cell thick so thin surface
  4. Close contact with blood vessels and increase diffusion
  5. Narrow so increase diffusion time as red blood cells slow down and have to squeeze through in a single file = keeps distance to diffusion
  6. Steep concentration gradient of oxygen and carbon dioxide between alveoli and capillaries maintained by constant ventilation of lungs with air and blood flow.
  7. Thin layer of fluid provides quicker diffusion as moist.
55
Q

What is the alveoli surrounded by

A

Capillaries

56
Q

What acts as a mass transport

A

The constant flow of internal medium (blood).

57
Q

When does diffusion happen quicker in alveoli

A

When surface is moist and large surface area

58
Q

How does gas exchange happen in the alveoli // describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs

A
  1. Oxygen from air moves down the trachea, bronchi, bronchioles and alveoli down a pressure gradient.
  2. Oxygen diffuses out of alveoli, across alveolar epithelium
    To the capillary endothelium and then the capillary itself down a diffusion gradient into haemoglobin in the blood.
59
Q

How does alveoli try to maintain a conc. gradient

A
  1. Blood needs to be taken away quickly.
  2. Movement of blood away and replaced with low conc.
  3. Ventilation of the lungs.
60
Q

Name two similarities and two differences between the gas exchange of an insect and a mammal

A

They both have a large surface area, Thin gas exchange surface, and a moist gas exchange surface. Concentration gradient achieved by ventilation.

The difference is in mammals there is a transport circulatory system. Not in insects.
Also respiratory surface in mammals is the alveoli, but in insects it is the junction between the tracheoles and the respiring tissues

61
Q

Suggest why gill lamella would not provide an efficient gas exchange surface on land

A

The surface area is reduced. The gills dry out. Prevents oxygen dissolving on the surface of the gills. No longer supported by water so the gills stick together with surface tension

62
Q

Smaller body mass means

A

Larger surface area to volume ratio

63
Q

Give two features of gills that allow efficient gas exchange

A

Counter current system which maintains concentration gradient.

Thin epithelium cell for short diffusion

64
Q

Why would small animals such as worms not need gills

A

Large surface area to volume ratio so diffusion occurs over body surface

65
Q

Explain how the structure of the gas exchange system of an insect insures that there is a large surface area for gas exchange

A

Many branched tracheoles.

66
Q

Give one way in which the transport of oxygen to a muscle in an insect is different from that in a fish

A

Blood is not involved in insects

67
Q

What give gills a large surface area

A

Lots of lamella on filaments

68
Q

Why do some fish underwater sway

A

Provide more water over the surface which maintains a concentration gradient

69
Q

Xerophytes adaptations

A
  1. Hairs so trap water vapour and water potential gradient decreased.
  2. Stomata in pits so trap water vapour and water potential gradient decrease.
  3. Thick cuticle layer so increased diffusion distance.
  4. Waxy cuticle so reduces evaporation.
  5. Folded leaves so trap water vapour and water potential gradient decreased.
  6. Spines and needles. so reduces surface area to volume ratio.

A Level Biology (9 decks)

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