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A-Level EDUQUAS Biology > Component 3: Gas Exchange > Flashcards

Component 3: Gas Exchange Flashcards

1
Q

What is the total oxygen requirement proportional to?

A

the volume of the organism

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2
Q

What is the rate of absorption of oxygen proportional to?

A

the organisms surface area

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3
Q

What are the common features of gas exchange surfaces?

A
  • large surface area relative to volume
  • permeable
  • thin
  • moist
  • mechanism to maintain diffusion gradients
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4
Q

What are the 3 main factors that affect the need for a specialised transport system?

A
  1. Volume -> an increase in the layers of cells means that less oxygen can diffuse into the organism (can only occur across 2 cells w/o specialised carriers) as it would be used up by outer cells first
  2. Level of Activity -> animals require the energy released by food in respiration to enable them to move around, if the animals is active or needs to keep warm the animal requires larger volumes of oxygen and nutrients to supply energy
  3. Surface area to volume ratio
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5
Q

Describe gas exchange generally for small organisms

A
  • don’t need a transport system
  • their cells are surrounded by the environment they live in
  • can rely on diffusion to supply the substances required
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6
Q

Describe gas exchange in amoeba

A
  • a single-celled organism that has a very large SA:V (pseudopodia) so that simple diffusion through cell membrane is fast enough to meet oxygen demands (short diffusion pathway)
  • lives in fresh water ponds
  • removes CO2 fast so cytoplasm doesn’t become acidic and enzymes can’t function
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7
Q

Describe gas exchange in flatworms

A

a multicellular organism with a smaller surface area to volume ration but are flattened to reduce diffusion distance and so they can rely on their external surface for gas exchange

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8
Q

Describe gas exchange in earthworms

A
  • a multi-cellular organism
  • smaller SA:V as it’s cylindrical but it’s elongated
  • diffusion happens across the moist skin but has a closed circulation with haemoglobin to carry oxygen to tissues and each cell
  • haemoglobin and circulation maintain a steep concentration gradient
  • since the ski has to stay moist it restricts the environment to damp soil
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9
Q

Why do terrestrial organisms have gas exchange organs inside the body?

A

to reduce water and heat loss

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10
Q

Describe the gas exchange in amphibians (e.g. frogs)

A
  • both terrestrial and aquatic
  • gas exchange takes place across the skin (at rest) and lungs (when active)
  • the skin is moist, permeable and has a well developed capillary network
  • undergoes metamorphosis when going from the larval form to the adult form
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11
Q

Describe the gas exchange in reptiles

A
  • gas exchange takes place across the lungs with in-growths of tissue to increase SA
  • movement of the ribs aid in the ventilation of the lungs
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12
Q

Describe the gas exchange in birds

A
  • gas exchange takes place in the lungs with air sacs
  • air sacs act as bellows, when the bird breathes in any air that remains in the lungs from the last breath gets sucked into air sacs = lungs always filed with fresh air
  • no diaphragm but ribs and flight muscles ventilate lungs
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13
Q

Describe the gills as the special respiratory surface in fish

A
  • one-way current of water kept flowing by ventilation mechanisms which maintains concentration gradient
  • large surface area provided by the gill filaments (density of water flowing through prevents gills from collapsing)
  • extensive network of blood capillaries to allow efficient diffusion and haemoglobin for oxygen carriage
  • thin layer of cells separate blood from outside water
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14
Q

Describe the gas exchange organ in bony fish?

A
  • called gills
  • fish possess several gills located between their buccal cavity (mouth cavity) and a chamber at the sides of their mouth called the opercular cavity
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15
Q

Compare bony fish to cartilaginous fish

A

Bony:

  • skeleton made of bones
  • lives in sea or fresh water
  • covered in scales (= no exchange through surface)
  • gills inside opercular cavity
  • gas exchange involves a counter-current system

Cartilaginous:

  • skeleton made of cartilage
  • mostly live in the sea
  • covered in scales
  • contain gill clefts
  • gas exchange involves a parallel system where the water and blood travel in the same direction
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16
Q

Draw a labelled diagram of a gill (bony fish)

A

Gill Arch: bony structure to support gill filaments and rakers

Gill Rakers: filter water and trap prey

Gill Filament (gas exchange surface): provides a large SA, filled with blood and short diffusion path (gill plates)

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17
Q

Why is water harder to respire in than air?

A
  • contains a low concentration of oxygen (1/30th of the concentration in air)
  • denser and more viscous than air making it harder to move in
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18
Q

What is the ventilation mechanism for taking in water?

A
  • mouth opens
  • operculum cavity closes
  • floor of the mouth is lowered
  • volume inside the mouth cavity increases
  • pressure inside the mouth cavity decreases
  • water flows in as the external pressure is higher than the pressure inside the mouth
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19
Q

What is the ventilation mechanism to force water out?

A
  • mouth closes
  • operculum opens
  • floor of the mouth is raised
  • volume inside the mouth cavity decreases
  • pressure inside the mouth cavity increases
  • water flows out over the gills because the pressure in the mouth cavity is higher than in the opercular cavity
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20
Q

What is meant by a counter current flow?

A

blood and water flow in opposite directions at the gill lamellae, maintaining the concentration gradient across the entire length

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21
Q

Why is counter current flow more efficient?

A

Concentration gradient maintained over entire distance of gill lamellae (diffusion occurs across entire length)

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22
Q

What is meant by parallel flow?

A

blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where its concentration in the blood and water is equal (50% max and not maintained across entire length)

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23
Q

Define the term ‘breathing’

A

the passage of air into and out of the lungs to supply the blood with oxygen

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24
Q

Define the term ‘ventilation’

A

movement of diaphragm and rib cage that brings air into and out of the lungs

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25
Q

Define the term ‘respiration’

A

the metabolic process by which an organism obtains energy by reacting O2 with glucose to give H2O, CO2 and ATP

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26
Q

What is the function of the human breathing system?

A

to supply respiring tissues with oxygen

reduce heat and water loss

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27
Q

Name and draw a diagram of the lungs

A
  • tongue
  • epiglotis
  • oesophagus
  • trachea
  • cartilage rings
  • ribs
  • intercostal muscles
  • bronchi
  • bronchioles
  • pleural membranes
  • pleural space
  • diaphragm
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28
Q

Why are the cartilage rings not complete?

A

allows the oesophagus behind it to bulge as food is being swallowed

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29
Q

Name the parts of the trachea section

A
  • larynx
  • trachea
  • rings of cartilage
  • bronchi
  • bronchioles
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30
Q

Draw and label the cross section of a bronchiole

A
  • smooth muscle
  • ciliated epithelium
  • loose tissue with elastic fibres
  • goblet cell
  • blood vessel
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31
Q

Draw and label the cross section of the trachea

A
  • cartilage
  • smooth muscle and elastic fibres
  • ciliated epithelium with goblet cells
  • small blood vessel
  • mucus secreting gland
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32
Q

What is the function of the goblet cells and positions in the gas exchange system?

A
  • secrete a sticky mucus which traps tiny particles in the air (e.g. pollen and bacteria)
  • this reduces the chance of infection as they are removed from the lungs
  • found in the trachea, bronchi and large bronchioles
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33
Q

What is the function of ciliated epithelial cells and positions in the gas exchange system?

A
  • cells have tiny hair like structures which waft the mucus up the airway to the back of the throat where it can be swallowed
  • trachea, bronchi and large bronchioles
34
Q

What is the function of cartilage and positions in the gas exchange system?

A
  • supports the trachea and bronchi by holding them open and preventing them from collapsing during pressure changes in inspiration or expiration
  • trachea, bronchi and large bronchioles
35
Q

What is the function of elastic fibres and positions in gas exchange system?

A
  • stretch during inhalation, the alveoli expand increasing the SA
  • elastic recoil of alveoli in expiration, helps force air out
  • found in trachea, bronchi, bronchioles and alveoli
36
Q

What is the function of smooth muscle and positions in the gas exchange system?

A
  • adjusts the size of the airways, it can contract which causes the constriction of airway, restricting flow
  • trachea, bronchi and bronchiole
37
Q

What are the parts of the alveoli?

A
  • branch of pulmonary vein
  • branch of pulmonary artery
  • capillary network
  • bronchiole
38
Q

State 5 ways in which the alveoli are efficient at gas exchange?

A
  1. provide a large surface area
  2. gases dissolve in the surfactant moisture lining the alveoli (moist)
  3. walls made of squamous epithelium, diffusion pathways is short
  4. extensive capillary network maintains diffusion gradients
  5. capillary walls are also one cell thick creating a short diffusion pathway for gases
39
Q

Why is the percentage of oxygen in expired air less than inspired air?

A

oxygen is absorbed into the blood at the alveoli for aerobic respiration

40
Q

Why is there a difference in the carbon dioxide concentration between inspired and expired air?

A

CO2 produced by aerobic respiration diffuses from the plasma into the alveoli to be exhaled

41
Q

Why does the percentage of nitrogen hardly change inspired and expired air?

A

nitrogen is neither absorbed or taken out of the blood, not needed

42
Q

Why is expired air saturated with water?

A

alveoli are permanently lined with moisture, evaporates from them and is exhaled

43
Q

What is surfactant and what is its function?

A
  • an “anti-sticking” mixture
  • prevents the alveoli collapsing during exhalation by reducing surface tension when the pressure inside is low
  • also allows gases to dissolve
44
Q

Describe the mechanism of inhalation in the lungs

A
  • external intercostal muscles contract, pulling the ribcage upwards & outwards
  • pulls out the pleural membranes, reducing pressure in the pleural cavity and the inner pleural membrane moves outwards
  • this pulls on the surfaces of the lungs and causes alveoli to expand (forced inspiration only)
  • diaphragm contracts, pulling it from a domed to a flattened shape
  • the combined effect is…
    • volume of the thorax and lungs increase
    • alveolar pressure is reduced to below atmospheric pressure
    • air drawn into lungs, going down the pressure gradient
45
Q

Describe the mechanism of exhalation in the lungs

A
  • external intercostal muscles relax and the ribcage falls under its own weight
  • diaphragm relaxes and gut pressure pushes back into its domed shape
  • the combined effect is…
    • volume of the thorax and lungs decrease
    • pressure is increased
    • air is forced out
46
Q

Describe the mechanism of forced exhalation in the lungs

A
  • internal intercostal muscles contract, pulling the ribcage down and in
  • abdominal muscle contracts pushing the diaphragm upwards
  • the combined effect is…
    • volume of the thorax and lungs decrease
    • pressure is increased
    • air is forced out
47
Q

How do the lungs stay ventilated?

A
  • negative pressure breathing and the movement of ribcage and diaphragm
  • lung is surrounded by the pleural membranes and the pleural cavity where the fluid lubricates movement and acts as a shock absorber
  • pleural membranes ensure the thorax is airtight, as changes in the volume of the thorax must be converted to pressure changes in the lung or ventilation wouldn’t occur
48
Q

Give an example of external gills

A
  • tadpoles (larval form of frogs)
  • highly branched
  • short diffusion path
  • vascularised (provide tissue with blood vessels)
  • movement provides water current
49
Q

How have insects adapted to live in arid habitats (terrestrial organisms)?

A
  • with all terrestrial organisms water evaporates from their body surface and risk dehydration
  • insects reduce water loss with a waterproof layer covering the body surface
  • exoskeleton made of chitin is impermeable and comprises a thin waxy layer over a thicker layer of chitin and protein
50
Q

Describe the gas exchange system in insects

A
  • the tracheal system
  • paired holes called spiracles on segments of the thorax and abdomen
  • they allow air to enter the system of chitin lined tubes called tracheae which branch into smaller tubes called tracheoles
  • spiracles can open and close so water loss is reduced (hairs covering spiracles help further with reducing water loss and stopping solid particles entering)
  • the ends of tracheoles are fluid-filled and close to muscle fibres, oxygen dissolves in the fluid directly into muscle cells
  • no respiratory pigment needed / blood circulation
51
Q

What is the difference in gas exchange for insects when they are resting vs when active?

A

Resting: rely on diffusion through spiracles, tracheae and tracheoles to take in oxygen and to remove carbon dioxide

Activity: movements of the abdomen ventilate the trachea

52
Q

What is the limitation of the tracheal system?

A

it limits the size of the insect as diffusion can only occur over small distances

53
Q

Why were insects much larger millions of years ago?

A
  • the oxygen concentration was so much higher than today
  • oxygen diffused more efficiently into the insect the cells so more energy is generated from respiration
  • this fuelled flight and growth
54
Q

What are the parts in a cross section in a leaf?

A
  • cuticle
  • upper epidermis
  • palisade mesophyll
  • spongy mesophyll
  • vascular bundle: xylem, phloem and bundle sheath parenchyma
  • air spaces
  • lower epidermis
  • stomata
  • guard cells
55
Q

Describe the pathway for gases into the leaf

A
  • gases diffuse through the stomata down a concentration gradient
  • then gases diffuse through the intracellular spaces between the mesophyll cells
  • gases dissolve in the film water covering the cells and in the cellulose and cell wall
  • then the gases diffuse into the cell
56
Q

Describe the role of the guard cell and stomata

A
  • control water loss

- allows exchange of gases inside and outside leaf

57
Q

Describe how the guard cells close the stomata (in the darkness)

A
  1. potassium ions diffuse out of the guard cells, down the concentration gradient
  2. malate is converted into starch
  3. both these processes raise the water potential of the guard cells
  4. water flows down its water potential gradient out of the cells
  5. Turgor of the guard cell reduces, the guard cells change shape and the stomata closes
58
Q

Describe how the guard cells open the stomata (in daylight)

A
  1. potassium ions move into the guard cells by active transport
  2. starch is converted into malate also lowering the water potential of guard cells
  3. water flows into the guard cells down the water potential gradient by osmosis
  4. turgor increases and the guard cell changes shape, opening stomata (inner wall is inelastic so they curve)
59
Q

State which direction the gases travel in daylight

A

Photosynthesis is dominant and respiration is still happening

  • CO2 in and O2 out
  • the CO2 produced by respiration can be used in photosynthesis but more CO2 is needed so CO2 diffuses in
  • some O2 is used in respiration but most diffuses out
60
Q

State which direction the gases travel in darkness

A

Respiration is dominant

  • O2 in and CO2 out
  • no photosynthesis
61
Q

Name 3 structural features of fish gills which make them efficient gaseous exchange organs

A
  1. Large surface area
  2. Short diffusion pathway/thin
  3. Good blood supply
62
Q

Explain the advantages to the fish with counter-current flow compared to parallel flow

A
  • blood saturation reaches a higher % level of saturation of oxygen
  • uptake continues throughout lamella as water concentration of oxygen is always higher than blood
  • concentration gradient is maintained across whole surface as blood always meet water with a higher oxygen concentration
63
Q

As the size of an organism increases which ratio decreases?

A

surface area:volume

64
Q

What is the role of the intercostal muscles in the thorax of a mammal?

A

move ribs/enlarge thorax

65
Q

Give 2 advantages to a mammal of having internal lungs

A
  • reduce heat (or water) loss

- protection by ribs

66
Q

Suggest how the expanding and compressing of an insects abdomen helps ventilate the tracheal system?

A

acting as a pump to draw air in via the thoracic spiracles through the system and foces it out via abdominal spiracles

67
Q

Explain why the long periods of closure of spiracles is important for an insects survival?

A

Reduces excessive water loss

68
Q

What do plants rely on?

A

SImple diffusion so they have lots of adaptations suited to it

69
Q

Describe and explain how terrestrial mammals are adapted for gaseous exchange in air

A
  • large number of alveoli to increase SA where gas exchange takes place
  • internal lungs to reduce water and heat loss
  • layer of moisture on alveoli for gases to dissolve in
  • thin walls reduce diffusion distance
  • blood supply maintains conc. between alveolar air and blood
  • haemoglobin transport oxygen
  • ventilation by diaphragm and rib cage enable stale air to be replaced by fresh air (ventilation mechanism)
70
Q

Describe 3 properties that all respiratory surfaces must posses and explain why they must have them

A
  1. thin - small diffusion distance
  2. large surface area - large contact with air for gas exchange
  3. moist - allows gases to dissolve/go into solution
71
Q

Give 2 reasons why gills don’t function effectively on land?

A
  1. unable to remain moist

2. they clump together because of surface tension and collapse

72
Q

What to say instead of ‘good blood supply’?

A 
rich/dense network of capillaries
concentration gradient (mechanism)
73
Q

State 2 advantages of using a tracheal system for gas exchange?

A
  1. No respiratory pigment (no haemoglobin required)

2. Oxygen supplied directly to tissues (no transport system needed)

74
Q

State 2 important structural features of alveoli

A
  1. large surface area
  2. One cell thick (thin)
    (3. large numbers of capillaries)
75
Q

Why have large, multicellular organisms evolved special surfaces for gaseous exchange?

A
  • Larger organisms need more O2 to meet metabolic needs
  • external surface becomes insufficient for gas exchange
  • diffusion distances are too large for O2 to reach cells furthest from surface
  • SA:V is too small
76
Q

Give 2 reasons why gills do not functionally effectively on land

A
  1. they are unable to remain moist

2. Gill filaments clump together due to surface tension

77
Q

How are plants adapted for harvesting light energy?

A
  • Palisade cells are elongated cells
  • are arranged in densely-packed layers/layer
  • contain many chloroplast cells and can arrange themselves according to light intensity (or to avoid bleaching)
  • light can pass through spongy mesophyll
  • large leaf surface area
78
Q

How are plants adapted for the inward diffusion of CO2?

A
  • Spaces between spongy mesophyll cells allows CO2 to diffuse to cells
  • Cells are moist so gases can dissolve
  • leaves are thin, short diffusion distance
  • thick waxy cuticle can reduce gaseous exchange
  • guard cells can change shape and reduce gaseous exchange
79
Q

How are plants adapted for the provision of water?

A
  • guard cells and stomata control water loss from plant (open and close with photosynthetic activity)
  • guard cells change shape
  • leaves covered by a thick waxy cuticle prevents water loss
80
Q

How are plants adapted for the removal of products of photosynthesis?

A
  • spaces between spongy mesophyll cells allows O2 to diffuse away

A-Level EDUQUAS Biology (24 decks)

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