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OCR A level Biology > 3.1.1 - Exchange and Transport > Flashcards

3.1.1 - Exchange and Transport Flashcards

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1
Q

Factors affecting exchange system

A

Size
SA:V ratio
Metabolic activity

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2
Q

How does size affect the need for an exchange system

A

In single-celled organisms, the cytoplasm is very close to its environment. Diffusion will supply enough O2 and nutrients to keep the cells alive and active

In multicellular organisms have several layers of cells, so there’s a longer diffusion pathway. Diffusion is too slow to enable a sufficient supply to the innermost cells

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3
Q

How does SA:V affect the need for an exchange system

A

When organisms have a large SA:V their SA is large enough to supply all the cells with sufficient O2

V increases more quickly than SA so the SA:V is smaller in larger organisms so a specialised exchange surface is needed

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4
Q

How does metabolic activity affect the need for an exchange system

A

Metabolically active organisms need good supplies of O2 and nutrients to supply energy for movement and warmth so the exchange of substances need to be efficient

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5
Q

Features of a good exchange surface

A

Large surface area - achieved by folding walls and membranes
Thin, permeable barrier - shorter diffusion distance
Good blood supply - maintain steep concentration gradient (brings molecules to supply side and removes from demand side)

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6
Q

How are lungs adapted

A

Many alveoli - large SA:V
Thin barrier - short diffusion pathway
Good blood supply (capillaries) to carry dissolved gases to and from alveoli
Ventilation refreshes air in alveoli
Elastic tissue to stretch/ recoil to help expel air

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7
Q

Function of goblet cells

A

Produce mucus

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8
Q

Function of cartilage

A

Prevent collapse of airways

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9
Q

Why do the walls of alveoli contain elastic fibres

A

Expand (inhalation) to increase lung volume
Prevent alveoli bursting
Elastic fibres recoil

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10
Q

Inspiration

A

Diaphragm contracts to move down and become flat. Displaces digestive organs downwards
External intercostal muscles contract moving the ribs outward and upward
Volume of thorax increases
Pressure in thorax < atmospheric pressure
Air is drawn in through the nasal passages, trachea, bronchi and bronchioles into lungs

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11
Q

Thorax

A

Chest cavity
Lined with pleural membranes - space between these membranes is the pleural cavity - usually filled with lubricating fluid

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12
Q

Expiration

A

Diaphragm relaxes and is pushed up by displaced organs underneath
External intercostal muscles relax and ribs fall
Volume of thorax decreases
Pressure in thorax > atmospheric pressure
Air is moved out of the lungs

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13
Q

What does the alveoli consist of

A

Thin, flattened epithelial cells alone with some collagen and elastic fibres

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14
Q

Elastic recoil

A

When the elastic fibres in the alveoli return to their resting size, they help squeeze the air out

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15
Q

What is the inner surface of the alveoli covered in

A

A thin layer of solution of water, salts and lung surfactant

When O2 diffuses out of the alveoli, it first dissolves in the water before diffusing into the blood. Water can also evaporate into the air in the alveoli

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16
Q

Lung surfactant

A

Phospholipid that coats the surfaces of the lungs

Without it, watery lining of alveoli would have surface tension —> collapse

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17
Q

Collagen in alveoli

A

Ensures alveoli aren’t deformed as they stretch (support)

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18
Q

Distribution and function of capillaries

A

Over surface of alveoli

To provide a large surface area for exchange

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19
Q

Distribution and function of cartilage

A

In walls of bronchi and trachea

To hold the airways open and provide structural support

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20
Q

Distribution and function of goblet cells

A

In ciliated epithelium

To produce and release mucus

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21
Q

Distribution and function of smooth muscle

A

In walls of airways

Contracts to constrict or narrow the airways

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22
Q

Loose tissue

A

Contains elastic fibres, glands and blood vessels

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23
Q

Peak flow meter

A

Simple device that measures how much air can move out of (and therefore into) the lungs

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24
Q

Spirometer

A

Device that measures the movement of air in and out of the lungs as the person breathes

Also measures oxygen consumption as the chamber of soda lime absorbs carbon dioxide

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25
Q

Vital capacity

A

Maximum volume of air that can be moved by the lungs in one breath
Measured by taking a deep breath and expiring all the air possible from the lungs
Usually in the region or 2.5-5.0 dm^3

26
Q

What does vital capacity depend on

A

The size of the person (particularly their height)
Their age and gender
Their level of regular exercise

27
Q

Tidal volume

A

Volume of air moved in and out with each breath
Usually measured at rest (0.5 dm^3) - sufficient to supply all the oxygen
Increases when exercising

28
Q

Residual volume

A

Volume of air that remains in the lungs even after forced expiration
Air remains in airways and alveoli
Approx. 1.5 dm^3

29
Q

Total lung capacity

A

Sum of vital capacity and residual volume

30
Q

Precautions to take when using a spirometer

A

Subject should be healthy and free from asthma
Wear a nose clip
Sterilise mouthpiece
No air leaks in apparatus - invalid/ inaccurate results
Don’t overfill water chamber - water may enter air tubes

31
Q

How do we know the volume of oxygen absorbed by the blood

A

We can assume that the volume of carbon dioxide released and absorbed by the soda lime is equal to the volume of O2

32
Q

How is breathing rate calculated

A

Counting the number of peaks in one minute

33
Q

Calculating oxygen uptake

A

Divide the difference between the first peak and last peak by the time (s)

34
Q

What will increases oxygen uptake result from

A

Exercise (more O2 and less CO2)

Deeper breaths

35
Q

Why do insects require a gas exchange system

A

Very active in life cycle

Tough exoskeleton through which little/ no gas exchange takes place

36
Q

Spiracles

A

Air opening in each segment of the insect

Allows air to enter inside the insect

37
Q

Why do insects frequently close their spiracles

A

To minimise water loss

38
Q

Insect tracheae

A

Leads away from the spiracles
Run both along and into the body of the insect
Carry air into the body

39
Q

What are insect tracheae lined with

A

Spirals of chitin which keeps them open if they are bent or pressed

40
Q

Why does little gas exchange take place in insect tracheae

A

Chitin is mostly impermeable to gases

41
Q

Tracheoles

A

Further branches of the tracheae
Vast number gives a large surface area
Some oxygen dissolves in moisture in the walls of the tube and diffuses into the surrounding cells

42
Q

Where is tracheole fluid found

A

In the ends of tracheoles

43
Q

Why do insects frequently close spiracles

A

To reduce water loss

44
Q

How do larger insects ventilate their tracheal system

A

Sections of the tracheal system can be expanded and contacted by flight muscles
Movement of wings can alter volume of the thorax
Abdomen volume can also be expanded then reduced

45
Q

Oxygen conc. in water is

A

Typically lower than that in air

46
Q

Operculum

A

Covers and protects the gills and is active in maintaining a flow of water over the gills

47
Q

Gill arch

A

Bony structure with two rows of gill filaments (primary lamellae) coming off it

48
Q

Gill filaments

A

Very thin and their surface is folded into many secondary lamellae

49
Q

Where does gas exchange take place in bony fish

A

Secondary lamellae - blood capillaries carry deoxygenated blood close to the surface

50
Q

Advantages of counter current flow

A

Absorbs maximum amount of oxygen from the water
Ensures steeper conc. gradients are maintained vs a parallel system
Bony fish can remove approx. 80% of O2 from the water

51
Q

Ram-ventilation

A

Only occurs when fish are moving

Fish open their mouths and operculums to keep a current of water flowing over their gills

52
Q

Buccal - opercular pump

A

Used when fish aren’t moving

53
Q

How does the buccal-opercular pump work

A

Base of mouth moves downward, lowering pressure in buccal cavity - water is drawn in
Mouth then closes, pressure of buccal cavity increases - pushing water through gills
At the same time, operculum opens, reducing pressure in opercular cavity helping water flow over gills

54
Q

Inspiratory capacity

A

The maximum volume of air that can be breathed in

55
Q

Function of ciliated epithelial

A

Move mucus

56
Q

Function of squamous epthelial

A

Provide a short dffusion distance

57
Q

Features of nasal cavity

A

Large SA w/ good blood supply - warms air to body temp
Hairy lining - secretes mucus to protect lung tissue from infection
Moist surfaces - Increase humidity of incoming air, reducing evaporation

58
Q

Bronchus

A

Division of trachea
Also has supporting rings of cartilage but much smaller
Ciliated cells but v. little goblet cells

59
Q

Bronchiole

A

No cartilage
Walls contain smooth muscle, contracts to constrict bronchioles, changes amount of air reaching lungs
Lined w/ thin layer of flattened epithelium

60
Q

Adaptations of gills

A

Large SA for diffusion
Rich blood supply to maintain conc gradient
Thin layers - short diffusion distance
Tips of adjacent gill filaments overlap - increases resistance to flow of water over gill surfaces and slows down movement of water - more time for gas exchange

61
Q

How is the steep conc gradient maintained in the lungs

A

Blood is constantly flowing through and out of lungs, bringing a fresh supply of RBC
Blood arrives in the lungs w/ a lower [O2] and a higher [CO2] than air in alveoli

OCR A level Biology (25 decks)

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