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OCR AS/A Level Biology A > Module 3.1 Exchange Surfaces and Breathing > Flashcards

Module 3.1 Exchange Surfaces and Breathing Flashcards

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1
Q

Do small organisms need a specialised surface for exchange?

A

No

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2
Q

Do large organisms need a specialised surface for exchange?

A

Yes, their body surface is no longer sufficient

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3
Q

🐿Small organisms have

A

A large surface area to volume ratio

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4
Q

🐘Large organisms have

A

A small surface area to volume ratio

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5
Q

A ratio should always be expressed as

A

Something to 1 (e.g. 4:1)

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6
Q

🌟Features of a good exchange surface

A
  1. Large surface area - more space for molecules to pass through = more efficient
  2. Thin barrier = diffusion distance reduced
  3. Permeable walls
  4. A good blood supply
  5. A fresh supply of molecules on one side and removal on the other - conc. grad. kept steep for quick diffusion
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7
Q

What are alveoli?

A

Tiny folds of lung epithelium to increase the surface area

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8
Q

What are bronchi or bronchioles?

A

Smaller airways leading into the lungs

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9
Q

What is the diaphragm?

A

A layer of muscle beneath the lungs

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10
Q

What are the intercostal muscles?

A

Muscles between the ribs. Contraction of the external intercostal muscles raises the ribcage.

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11
Q

What is the trachea?

A

The main airway that leads from the back of the mouth to the lungs

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12
Q

💨Oxygen

A

passes from the air in the alveoli to the blood in the capillaries

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13
Q

🌬Carbon dioxide

A

passes from the blood to the air in the alveoli

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14
Q

What does the surfactant do?

A

It lines the alveoli and reduces the cohesive forces between the water molecules, as these forces tend to make the alveoli collapse

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15
Q

Adaptions to reduce the diffusion distance:

A
  1. The alveolus walls are one cell thick
  2. The capillary walls are one cell thick
  3. Both walls consist of squamous cells (flattened or v thin cells)
  4. The capillaries are v close to the alveolus walls
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16
Q

The concentration of carbon dioxide in the blood is

A

higher than that in the air of the alveolus. This means that carbon dioxide diffuses into the alveoli

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17
Q

The concentration of oxygen in the blood is

A

lower than that in the alveoli, so oxygen diffuses into the blood

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18
Q

Ventilation ensures that:

A
  1. The concentration of oxygen in the air of the alveolus remains higher than that in the blood
  2. The concentration of carbon dioxide in the alveoli remains lower than that in the blood
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19
Q

🌟During Inspiration..

A
  1. The diaphragm contracts, flattens and moves down
  2. The external intercostal muscles contact
  3. The ribs move up
  4. The volume in the chest cavity increases
  5. The pressure in the chest cavity drops below atmospheric pressure
  6. Air enters the lungs
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20
Q

🌟During Expiration…

A
  1. The diaphragm relaxes and moves up
  2. The external intercostal muscles relax
  3. The ribs move down
  4. The internal intercostal muscles can contract (to help push air out more forcefully)
  5. The volume in the chest cavity decreases
  6. The pressure in the lungs rises above atmospheric pressure
  7. Air exits the lungs
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21
Q

What is cartilage?

A

A form of connective tissue

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22
Q

What are ciliated epithelium?

A

A layer of cells that have lots of cilia (hair-like projections)

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23
Q

What are elastic fibres?

A

Protein fibres that can deform and recoil

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24
Q

What are goblet cells?

A

Cells that secrete mucus

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25
Q

What is smooth muscle?

A

Muscle that involuntarily contracts

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26
Q

What is the function of cartilage?

A

To keep the airways open and prevent collapse during inspiration when there is low pressure in the thorax. They also allow some flexibility in the neck

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27
Q

What is the function of smooth muscle?

A

To contract to constrict the airways, to reduce air flow and therefore reduce the amount of harmful substances going into the lungs

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28
Q

What is the function of elastic fibres?

A

To stretch when the smooth muscle contracts and to recoil when the smooth muscle relaxes to help dilate the airway

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29
Q

What is the function of goblet cells?

A

To secrete mucus to trap bacteria and other particles to be removed from the lungs (reducing infection)

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30
Q

What is the function of ciliates epithelium?

A

To waft to remove mucus from the airway up to the threat

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31
Q

What is the function of blood vessels?

A

To supply lung tissue with oxygen for aerobic respiration

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32
Q

🌟What structures does the trachea have?

A

Cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres

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33
Q

🌟What structures do the bronchi and bronchioles have?

A

Cartilage (only in bronchi), ciliated epithelium, goblet cells, smooth muscle and elastic fibres

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34
Q

🌟What is the only structure that alveoli have?

A

Elastic fibres

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35
Q

What happens during inspiration when using a spirometer?

A

Air is drawn in from the chamber and the lid moves down

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36
Q

What happens during expiration when using a spirometer?

A

The air returns to the chamber, raising the lid

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37
Q

What is the point of soda lime chamber connected to a spirometer?

A

To absorb the carbon dioxide

38
Q

What precautions should be taken when using a spirometer?

A
  1. Ensure the subject is healthy
  2. The soda lime should be fresh and functioning
  3. There should be no air leaks in the apparatus
  4. The mouthpiece should be sterilised
  5. The water chamber shouldn’t be overfilled (otherwise water may enter the air tubes)
39
Q

🐠What is the buccal cavity on a fish?

A

The mouth

40
Q

🌊What is a countercurrent flow?

A

When 2 fluids flow in opposite directions

41
Q

What are gill filaments? (Also known as primary lamellae)

A

Tissue that makes up the gill.

42
Q

What are lamellae? (Also known as secondary lamellae or gill plates)

A

Folds of the filament that increase the surface area

43
Q

What is the operculum?

A

A bony flap that covers and protects the gills

44
Q

What is the spiracle?

A

An external opening to allow air in or out of the trachea

45
Q

What is tracheal fluid?

A

Fluid found at the ends of the tracheoles

46
Q

How many gills do bony fish have?

A

5 pairs

47
Q

What are the gills covered by?

A

A bony plate called the operculum

48
Q

Why is a countercurrent flow important?

A

To ensure the max. amount of oxygen is absorbed

49
Q

🐝Do insects have an open or closed circulatory system?

A

Open

50
Q

Describe how gas exchange occurs in insects

A
  1. Air enters a spiracle
  2. Air enters the trachea and moves into the tracheoles
  3. The ends of the tracheoles are open and filled with tracheal fluid
  4. Gaseous exchange occurs between the air in the tracheole and the tracheal fluid
  5. Some also occurs with the wall
51
Q

What can happen when insects are very active?

A

The tracheal fluid can be withdrawn, increasing the surface area of the tracheole wall exposed to air. This means more oxygen can be absorbed.

52
Q

Name 3 ways in which ventilation can be achieved by insects

A
  1. Sections of the tracheal system are expanded and have flexible walls
  2. Movements of the wing can alter the volume in the thorax
  3. Locusts can alter the volume in their abdomen by specialised breathing movements
53
Q

☄️What causes asthma?

A

The bronchioles constricting unnecessary

54
Q

What is an exchange surface?

A

A specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other

55
Q

A good exchange surface has:

A
  1. A large surface area
  2. Thin barriers (shorter diffusion distance)
  3. A fresh supply of molecules on one side keeps the concentration high
  4. Permeable
  5. Removal of required molecule on the other side
56
Q

Large, active organisms have specialised exchange surfaces because

A

There is a higher demand for oxygen and so a high need for carbon dioxide to be removed. There is a small surface area to volume ratio and the distance would be too large to supply the need. The surface area is too small

57
Q

How do you calculate surface area to volume ratio?

A

Surface area divided by volume

58
Q

What is gaseous exchange?

A

The movement of gases by diffusion between the organism and its environment across a barrier

59
Q

What is a tissue?

A

A group of similar cells working together to perform a common function

60
Q

🌊What is tidal volume?

A

Volume of air moved in and out of the lungs with each breath at rest

61
Q

What is vital capacity?

A

Largest volume of air that can be moved in and out of the lungs in one breath

62
Q

What is residual volume?

A

Volume of air that always remains in the lungs even after the largest possible exhalation

63
Q

What is inspiratory reserve volume?

A

The volume of air that can be breathed in above the normal tidal volume

64
Q

What is expiratory reserve volume?

A

The volume of air that can be breathed out above the normal tidal volume

65
Q

🌊How to measure mean tidal volume?

A

Get the patient to breath normally (not through nose). Measure the height of the waves at least 3 times from the trace. To calculate the mean, add the volumes together and divide by the number of breaths

66
Q

How to calculate breaths per minute?

A

Count the number of breaths taken in a set time period. Divide the number of breaths by the time. Times the answer by 60 to get breaths per minute

67
Q

How do you measure rate of oxygen uptake?

A

Calculate the difference in volume between either 2 peaks or 2 troughs. Divide the volume by the time taken. Times by 60 to get the rate per minute

68
Q

Describe the process of ventilation in fish🐠

A
  1. The mouth opens (the operculum is closed)
  2. The buccal cavity floor is lowered
  3. This increases the volume and decreases the pressure of the buccal cavity compared to outside
  4. Water rushes into the mouth down a pressure gradient
  5. The opercular cavity expands (which lowers the pressure)
  6. The buccal cavity floor is raise (which increases the pressure)
  7. The pressure inside the buccal cavity is now higher than in the opercular cavity
  8. Water moves from the buccal cavity over the gills into the opercular cavity
  9. The mouth is now closed and the operculum opens
  10. The sides of the opercular cavity move inwards, increasing the pressure
  11. Water rushes out of the fish through the operculum
69
Q

When the size of an organisms increases..

🦂🐢🐑🦁🐘🐋

A

It’s volume and surface area also increase but the surface area doesn’t increase as much as the volume

70
Q

Surface area=

A

Length * width * no. of sides

71
Q

Volume=

A

Length * width * height

72
Q

Why is the tracheal fluid withdrawn when insects are active?

A

It allows a larger surface area for exchange (because there is a larger surface area of the tracheole exposed to surrounding tissues)

73
Q

Give one similarity between the way in which oxygen from the atmosphere reaches a muscle in an insect and the way it reaches a mesophyll cell in a leaf 🍃

A

Oxygen diffuses directly into the cells

74
Q

Explain how the fish increases pressure in the buccal cavity

A

The floor of the buccal cavity raises which decrease the volume in the buccal cavity and increases the pressure 🐟

75
Q

What size organisms need specialised gas exchange surfaces?

A

Large multicellular organisms

76
Q

Why does a specialised gas exchange surface need a rich blood supply?

A

A rich blood supply means oxygen is supplied rapidly and waste is taken away rapidly. It helps provide sufficient gases quickly enough for all metabolic reactions.

77
Q

Describe the specialised gas exchange surface in plants

A

Gases enter and leave via the stomata. There are large gas spaces between the spongy mesophyll cells. 🌱

78
Q

What is the function of the smooth muscle in the wall of the bronchus?

A

The smooth muscle contracts, restricting the lumen in the bronchus, reducing air flow and therefore reducing the amount of harmful gases going into the lungs.

79
Q

How are blood capillaries involved in gas exchange?

A

Blood capillaries help to maintain a high concentration gradient of gases in the alveoli so oxygen diffuses into the capillaries and carbon dioxide diffuses out.

80
Q

Inflammation caused by 🚬 smoke causes enzymes to break down the elastic fibres of the alveoli. This can lead to a condition called emphysema.
Suggest how the structure of the alveoli of a person with emphysema is different to that of a person without emphysema.

A

The surface area for gas exchange will be smaller, the would be fewer elastic fibres and elastic fibres being broken down could cause alveoli to merge.

81
Q

Which statements are true?

1) During expiration, the volume in the thorax increases.
2) During inspiration, the pressure in the thorax decreases.
3) During expiration, the external intercostal muscles relax.
4) During inspiration, the diaphragm becomes dome shaped.

A

Statements 2 and 3 only

82
Q

Why is it important to change the pressure inside the thorax during expiration?

A

The pressure in the thorax increases during expiration above atmospheric pressure, forcing air out of the lungs (as air moves from high to low pressure)

83
Q

Why can’t all air be removed from the lungs?

A

Air remains in the bronchi/bronchioles, some air remains in the alveoli as they cannot be completely flattened due to the surfactant.

84
Q

Explain why the trace on a spirometer goes diagonally down

A

The chamber rises and falls when the person breathes. Carbon dioxide is absorbed by the soda lime, meaning that the volume of air in the chamber gradually decreases over time so the air chamber doesn’t rise as high.

85
Q

What word describes the type of circulatory system insects have?

A

Open

86
Q

Describe the movement of blood and water in the gills of bony 🐟

A

The blood flows into the secondary lamellae in the opposite direction to the flow of 💦 over the lamellae. This creates a countercurrent flow to absorb the max amount of oxygen.

87
Q

🌟Why larger organisms need transport systems and specialised surfaces for exchange

A

Large organisms are more active = higher demand for oxygen

Larger organisms have smaller surface-area-to-volume ratios = diffusion too slow

Diffusion distance is too great - many cells are deep in the body and not in contact with the environment

Insufficient waste would be removed

88
Q

🌟How the lungs are adapted for efficient exchange

A

Large SA - millions of alveoli - more space for O2 and CO2 to diffuse

Thin barrier (only 2 cells thick) - alveoli walls 1 cell thick + capillary walls 1 cell thick, walls of alveoli and capillaries made of squamous epithelial cells, capillaries and alveoli in close contact, RBCs squeezed against wall of capillaries (v narrow) = closer to air in alveoli and reduces rate of flow

Permeable - plasma membranes of the cells lining the alveoli and capillaries are fully permeable to O2 and CO2

89
Q

🌟Tissues in the trachea, bronchi and bronchioles

A

C shaped rings of cartilage (not in bronchioles):

  • keep airways open, prevent collapse during inspiration (low pressure in the thorax)
  • some flexibility

Smooth muscle:

  • contracts to constrict airways
  • reduces flow of air (and therefore reduces harmful substances going into the lungs)

Elastic fibres:

  • DO NOT CONTRACT AND RELAX
  • stretch when smooth muscle contracts
  • recoils when smooth muscle relaxes to help dilate the airway again

Goblet cells: (not in v small bronchioles)
-secrete mucus - traps bacteria and particles to be removed from the lungs - reduces infection

Ciliated epithelium:
-waft to and fro - moves mucus from airways up to throat

Blood vessels:
-supply lung tissue with oxygen for aerobic respiration

90
Q

🌟Tissues in the alveoli

A

Elastic fibres:

  • DO NOT CONTACT OR RELAX
  • stretch during inspiration to inc. lung volume and prevent alveoli from bursting
  • recoil during expiration to expel more air from the alveoli

Squamous epithelium:
-alveoli walls one cell thick = short diffusion distance for gaseous exchange

91
Q

🌟Using a spirometer to measure mean tidal volume

A
  • Don’t breathe through nose
  • Patient breathes normally
  • Measure height of waves (tidal volume) for at least 3 waves from the trace
  • Calculate mean (add volumes together then divide by number of breaths)
92
Q

🌟Why the volume of oxygen in the spirometer decreases over time

A
  • when you exhale into the spirometer, the carbon dioxide is absorbed by the soda lime
  • this decreases the volume of gas in the spirometer meaning the trace line falls gradually
  • the volume of carbon dioxide used up is equal to the volume of oxygen used by the person
  • this means we can measure rate of oxygen uptake

OCR AS/A Level Biology A (14 decks)

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