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OCR Biology A Level > 3.1.1 Exchange Surfaces > Flashcards

3.1.1 Exchange Surfaces Flashcards

1
Q

Why do larger more active organisms require specialised gas exchange surfaces?

A
  • higher demand for oxygen
  • greater need to remove carbon dioxide
  • have a smaller SA:VOL ratio
  • diffusion distance too great to just use SA
  • diffusion alone wouldn’t meet needs of organism
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2
Q

Why don’t smaller more active organisms require specialised gas exchange surfaces?

A
  • lower demand for oxygen
  • lesser need to remove carbon dioxide
  • have a larger SA:VOL ratio
  • diffusion distance small enough to just use SA
  • diffusion alone meets needs of organism
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3
Q

What factors affect rate of diffusion?

A
  • temperature
  • concentration gradient
  • stirring movement
  • surface area
  • diffusion distance
  • size of molecule
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4
Q

Explain the structure of trachea

A
  • supported by cartilage c-ring - prevents collapse during low air pressure
  • elastic fibers allow stretch, preventing bursting
  • smooth muscle fibres can contract to reduce the diameter of the trachea
  • goblet cells release mucus - trapping pollen/bacteria
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5
Q

Explain the structure of bronchi

A
  • similar structure to trachea - smaller diameter + thinner walls
  • complete rings of cartilage - doesn’t lie against the oesophagus
  • larger bronchioles have muscle cells
  • smaller bronchioles have no muscle cells
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6
Q

Explain the structure of alveoli

A
  • arranged in groups at end of small bronchioles
  • walls consist of squamous epithelium cells - short diffusion distance
  • elastic fibres allow for stretching - prevents bursting
  • water fluid lining - produces surface tension
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7
Q

Explain the structure of ciliated epithelial tissue

A
  • columnar
  • have cilia
  • line the trachea, bronchi and larger bronchioles
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8
Q

What is the rib cage?

A

Provides a semi-rigid case within which pressure can be lowered with respect to the air outside

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9
Q

Explain the different muscles used for ventilation

A

External Intercostal Muscle
- when these contract, the ribcage moves up + out - opposite when relaxed
Internal Intercostal Muscle
- when you exhale forcibly using energy these contract, pulling ribs down hard and fast
Diaphragm
- broad, doamed sheet of muscle which forms the floor of the thorax

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10
Q

Explain the mechanism of inspiration

A
  • external intercostal muscles contract
  • ribcage moves up + out
  • diaphragm contracts + moves down
  • thorax volume increases
  • pressure in thorax decreases below atmospheric pressure - air flows in
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11
Q

Explain the mechanism of expiration

A
  • external intercostal muscles relaxes
  • ribcage moves down + in
  • diaphragm relaxes + moves up
  • thorax volume decreases
  • pressure in thorax increases above atmospheric pressure - air flows out
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12
Q

What is pulmonary ventilation and how is it calculated?

A

The volume of air breathed in during 1 minute

Pulmonary ventilation = ventilation rate x tidal volume

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13
Q

What is tidal volume?

A

The volume of air inhaled or exhaled in one breath during steady/regular breathing

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14
Q

What is inspiratory + expiratory volume?

A

The additional volume of air that can be inhaled/exhaled after normal inspiration/expiration.

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15
Q

What is vital capacity?

A

The maximum volume of air inhaled or exhaled in one breath - reserve + tidal capacity = vital capacity

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16
Q

What is total lung capacity

A

The maximum volume of air that can fill the lungs

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17
Q

What is residual volume?

A

Air stuck in the lungs - thorax/ribcage cannot be completely flattened

18
Q

Explain key aspects of using a spirometer

A
  • person attached via tube to air chamber
  • chamber contains oxygen, sits on top of water
  • moves up during expiration, down during inspiration
  • traced on graph
  • contains soda lime - removes CO2
  • nose clip ensures all air goes through chamber - no invalid result due to breathing out through nose
19
Q

List safety precautions when using a spirometer

A
  • use medical grade oxygen
  • disinfect mouthpiece
  • person is healthy/ not asthmatic
  • ensure chamber can move
20
Q

List features of an efficient exchange system and how they are achieved

A
  • increased surface area (e.g. root hair cells)
  • thin layer (e.g. alveoli)
  • good blood supply to maintain steep concentration (e.g. gills/alveolus)
21
Q

How does air enter into insects?

A

Through spiracles in the thorax + abdomen

22
Q

How can spiracles be opened and closed?

A

Sphincters

23
Q

Where does air flow after entering spiracles, and give key aspects

A
  • leads into tracheae (1mm diameter)
  • run into and along the insect body
  • supported by circular bands of chitin (NOT C-shaped)
  • impermeable to gases
24
Q

Where does air flow after entering trachea, and give key aspects

A
  • leads into tracheoles (0.6-0.8 μm diameter)
  • single, greatly elongated cells
  • no chitin lining
  • freely permeable to gases
  • run between individual cells
25
Q

How does air move along the tracheal system?

A
  • mostly diffusion alone
  • due to vast number of tracheoles giving a large SA for gaseous exchange
26
Q

How does oxygen get into surrouding cells from the system?

A
  • dissolves into the moisture of the walls
  • then diffuses into cells
27
Q

What prevents pentration of air at the end of tracheoles

A

Tracheal fluid

28
Q

How do insects decrease ther amount of fluid limiting diffusion of air?

A
  • lactic acid builds in tissue during movement (e.g. flying)
  • water moves from high ψ in tracheoles to low ψ in tissues (osmosis)
  • more surface area exposed for gaseous exchange
29
Q

Explain how insects move more air into + around the tracheal system

A
  • mechanical ventilation
  • muscular pumping of thorax + abdomen
  • changes volume of body, subsequently changing pressure of tracheae + tracheoles
  • breathing in = volume increases - lower pressre inside than out - air drawn in
  • breathing out = volume decreases - higher pressre inside than out - air forced out
30
Q

How else can insects store air?

A
  • air sacs
  • inflated + deflated by ventilating movements
31
Q

What is fluttering and why could insects do it?

A
  • pattern of opening + closing spiracles
  • may reduice water loss by evaporation
32
Q

Why do bony fish require specialised exhange surfaces?

A
  • large organisms so have a small SA:VOL ratio
  • concentration of oxygen in water much lower than air
  • water much more viscous than air so lungs not appropriate
33
Q

Describe the movement of water through the gills of a fish

A
  • water moves from outside of fish through open mouth
  • into buccal cavity
  • into opercular cavity
  • over gills
  • out of fish through open opercular valve
34
Q

Explain the alternative system fish uses to ventilate

A
  • mouth and operculum open alternativley
35
Q

Explain what happens when the mouth is open

A

Mouth Open
- buccal cavity lowered
- volume of buccal cavity increases
- pressure of buccal cavity decreases
- water moves into cavity
- opercular valve shut
- opercular cavity containg gills expands - lowers pressure
- floor of bucal cavity moves up, increasing pressure
- water moves over gills due to pressure difference

36
Q

Explain what happens when the mouth is closed

A

Mouth Closed
- sides of opercular cavity move inwards - decreasing pressure
- increase pressure in opercular cavity forces water over gills + out operculum
- floor of buccal cavity moved up, maintaining flow over gills
- when buccal cavity is lowered, operculum sucked shut

37
Q

List features of bony fish that allow for efficient gaseous exchange

A
  • gills have larger SA - large area for diffusion to occur
  • gills have rich blood supply - steep concentration gradient
  • gills have thin layers - short diffusion distance
38
Q

Explain the structure of gills

A
  • each gill made of 4 bony arches
  • arches lined with gill filaments (thin + flat)
  • gill filaments occur in stacks called gill plates
  • filaments have lamellae - increased SA
39
Q

How do neighbouring gill filaments interact to increase gaseous exhange?

A
  • overlap at their tips
  • provides resistance to water flow
  • water slowed down
  • more time for gaseous exchange
40
Q

What is counter current and how does it work?

A
  • water moves over gills + blolod flows in gill filaments in opposite directions
41
Q

Compare concurrent and counter-current systems

A

Concurrent/ Parrallel Flow
- water + blood flow together
- equilibirum quickly reached
- no further diffusion

Counter-Current
- blood flowing past water of higher oxygen concentration
- diffusion occurs all along gill
- equilibrium never reached

42
Q

Compare bony fish and cartilaginous fish

A

Bony Fish
- e.g. trout/cod
- skeleton made from bone
- counter-current exchange system
- remove ~80% of oxyegn from water flowing over gills

Cartilaginous Fish
- e.g. sharks/rays
- skeleton made from cartilage
- parrallel exhange system
- remove ~50% of oxygen from water flowing over gills

OCR Biology A Level (13 decks)

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