3.1.1 - Exchange surfaces

Question 1

Why are specialised exchange surfaces mainly required by multicellular organisms ?

Answer 1

• Small surface area : volume ratio
• Large size
• High metabolic demands

Question 2

Why do multicellular organisms require specialised exchange surfaces due to size and surface area: volume ratio ?

Answer 2

• As the size increases, the surface area : volume ratio decreases
• There is less surface area for the absorption of nutrients and gases and secretion of waste products
• This menas the diffusion distance is too large for solely the rate of diffusion to be sufficient and provide all cells with required nutrients and molecules

Question 3

Why do multicellular organisms require specialised exchange surfaces due to high metabolic demands ?

Answer 3

• As the size/mass of an organism increases, the higher their metabolic demands
• Ov2 is required by all cells for aerobic respiration
• Carbon dioxide is a toxic waste product of aerobic respiration that needs to be removed

Question 4

Why do single-called organisms not require specialised exchanges surfaces ?

Answer 4

• They have a small size, meaning they have a large surface area : volume ratio
• There is a large surface area for absorption of nutrients and gases/ secretion of waste products
• The diffusion distance is not too large and solely the rate of diffusion is sufficient to provide cells with all required nutrients and molecules
• Due to small size/ mass they have low metabolic demands

Question 5

What is the relationship between size and surface area : volume ratio ?

Answer 5

As the size of an object increases, the surface area : volume ratio decreases

Question 6

Do you know how to calculate surface area : volume ratio ?

Answer 6

Yes

Question 7

What are features of exchange surfaces ?

Answer 7

• Large surface area
• Short diffusion distance
• Good blood supply
• Ventilation mechanism

Question 8

Explain how increased surface area is a feature of efficient exchange surfaces ?

Answer 8

• This provides a large surface area over which diffusion can occur
• This results in a greater overall net movement of particles per time period, increasing rate of diffusion

Question 9

Explain how root hair cells having an increased surface area makes them more efficient exchange surfaces ?

Answer 9

• Root hair cells are responsible for the absorption of water and mineral ions from the soil
• They have a root hair that increases their surface area, this results in a greater rate of diffusion/ water uptake via osmosis

Question 10

Explain how thin layers is a feature of efficient exchange surfaces ?

Answer 10

• This results in a shorter diffusion distance
• Particles move across a short diffusion distance at a faster rate resulting in a Greste rate movement of particles per time period, causing the rate of diffusion to increase

Question 11

Explain how the alveoli having a short diffusion distance makes them more efficient exchange surfaces ?

Answer 11

• Alveoli are responsible for the exchange of Ov2 and COv2 between the alveoli and the capillaires in the lungs
• They are one cell thick, resulting in a short diffusion distance
• This results in a a greater rate of diffusion of Ov2/ COv2, maximising gas exchange

Question 12

Explain how a good blood supply is a feature of efficient exchange surfaces ?

Answer 12

• This means a steep concentration gradient is maintained
• This results in a greater overall net movement of particle per time period, causing the rate of diffuse to increase

Question 13

Explain how the alveoli having a good blood supply makes them more efficient exchange surfaces ?

Answer 13

• Oxygenated blood is continually brought away from the alveoli/ deoxygenated blood is continually brought towards them
• This maintains a steep concentration gradient, increasing the rate of diffusion and efficiency of gas exchange

Question 14

Explain how gills having a good blood supply makes them more efficient exchange surfaces ?

Answer 14

• Blood flows in the opposite direction to the flow of water, creating a counter-current system
• This maintains a steep concentration gradient along the whole length of the capillary
• This causes the rate of diffusion to increase, maximising gas exchange

Question 15

Explain how ventilation mechanisms are features of efficient exchange surfaces ?

Answer 15

• This maintains a steep concentration gradient
• This results in an overall grater net movement of particles per time period, increasing the rate of diffusion

Question 16

Explain how alveoli having a ventilation mechanism makes them more efficient exchange surfaces ?

Answer 16

• This ensures a steep concentration gradient of Ov2 / COv2 is maintained between air in alveoli and blood in capillaries
• This results in a greater net movement of particles per time period, causing the rate of diffusion to increase maximising gas exchange

Question 17

What are the components of the respiratory system ?

Answer 17

• Nasal cavity/ passage way
• Trachea
• Bronchus
• Lungs
• Bronchioles
• Alveoli

Question 18

What are the adaptations of the nasal cavity ?

Answer 18

• Large surface area with good blood supply : Increases temperature of incoming air
• Hairy lining : Lining of epithelial cells and goblet cells that secrete mucus to trap dust and bacteria
• Moist surfaces : Increases humidity of incoming air

Question 19

What is the role of the nasal cavity ?

Answer 19

Ensures incoming air is a similar temperate and humidity than air already in the body/ lungs

Question 20

What are features of the trachea ?

Answer 20

• Trachea are supported by incomplete rings of cartilage
• It is lined with ciliated epithelium and goblet cells
• The wall of the trachea contains smooth muscle and elastic fibres

Question 21

What is the function of the incomplete rings of cartilage in the trachea ?

Answer 21

They offer support and prevent the trachea from collapsing

Question 22

What is the role of goblet cells in the trachea ?

Answer 22

• Goblet cells secrete mucus which traps dust, bacteria and other microorganisms
• This prevents them from reaching the lungs

Question 23

What is the role of the ciliated epithelium in the trachea ?

Answer 23

• Cilia beat rhythmically and sweep mucus, dust and bacteria upwards and away from the lungs
• This is then swallowed and digested int he stomach

Question 24

What are the features of bronchi ?

Answer 24

• Similar structure to trachea but have thinner walls and smaller diameter
• Contain cartilage
• Walls of bronchi contain smooth muscle and elastic fibres
• They are lined with ciliated epithelium with goblet cells

Question 25

What are the features of bronchioles ?

Answer 25

- They typically don’t have cartilage - They are lined with ciliated epithelium BUT NOT GOBLET CELLS - Walls of bronchioles contain smooth muscle and elastic fibres

Question 26

What is the role of smooth muscle and elastic fibres in bronchioles ?

Answer 26

- Allow bronchioles to adjust the size of their lumen/ airway by smooth muscle contracting/ relaxing - This increases/ decreases airflow to the lungs

Question 27

What are the features of alveoli ?

Answer 27

- Alveoli wall consists of one layer of epithelium ( one cell thick ) - Contain elastic fibres - They have an extensive capillary network

Question 28

What is the role of elastic fibres in the alveoli ?

Answer 28

- ELASTIC RECOIL OF ALVEOLI - Allow alveoli to stretch and return to resting size as air is drawn in and out of the lungs

Question 29

What are the main adaptations of the alveoli ?

Answer 29

- Large surface area - Short diffusion distance - Good blood supply - Ventilation system

Question 30

Explain the effect of a large surface area on alveoli ?

Answer 30

- Due to the large number of alveoli in the lungs, they have a large surface are - This means there is a large surface area over which gas exchange / diffusion of Ov2/ COv2 can occur - This results in a n increased rate of diffusion/ maximising gas exchange

Question 31

Explain the effect of a ventilation system on alveoli ?

Answer 31

- The constant movement of air in and out of the lungs maintains a steep concentration gradient between the air in the lungs and blood - This increases the rate of diffusion, maximising efficiency of gas exchange

Question 32

Label the diagram ?

Answer 32

Question 33

Label the diagram ?

Answer 33

Question 34

What type of process is inspiration ?

Answer 34

Inspiration is an active process that requires/ used energy

Question 35

Explain what happens during inspiration/ inhalation ?

Answer 35

- External intercostal muscles contract, moving ribs out and up - Diaphragm contracts and flattens - This causes the volume of the thorax to increase which causes the pressure of the thorax to decrease - Pressure in thorax is lower than pressure of atmospheric air so air moves into the lungs/ air is drawn in until pressure equalises outside and inside the chest

Question 36

What type of process in expiration ?

Answer 36

Expiration is a passive process that does not require/ use energy

Question 37

Explain what happens during expiration/ exhalation ?

Answer 37

- External intercostal muscles relax, ribs move down and in due to gravity - Diaphragm relaxes, moves up and becomes dome-shaped - This causes the volume of the thorax to decrease which causes pressure in the thorax to increase - Pressure in the thorax is greater than pressure of atmospheric air so air moves out/ is forced out of the lungs until pressure inside and outside the chest equalises

Question 38

When does expiration require energy ?

Answer 38

You can exhale forcibly which uses energy

Question 39

Explain what happens during active expiration / exhalation ?

Answer 39

- Internal intercostal muscles contract, pulling ribs down and back - Abdominal muscle contract, pushing organs up against digraph increasing internal pressure - This causes forced exhalation

Question 40

What can be used to measure the capacity of the lungs ?

Answer 40

Spirometer

Question 41

Explain how a spirometer is used to make breathing measurements ?

Answer 41

- The patient breathes in and out through the spirometer - COv2 from exhaled breath is absorbed by soda lime to prevent concentration of COv2 in rebreathed air from being too high, causes respiratory distress - As the subject breathes through the spirometer, a graph is formed digitally, which can be viewed on a computer

Question 42

Label the different parts of the graph produce by the spirometer ?

Answer 42

Question 43

Define the term 'Tidal volume' ?

Answer 43

Tidal volume : The volume of air that moves in/ out of lungs with each resting breath

Question 44

Define the term 'Vital capacity' ?

Answer 44

Vital capacity : The maximum volume of air that can be breathed in when the strongest possible exhalation is followed by the strongest possible inhalation

Question 45

Define the term 'Inspiratory reserve volume' ?

Answer 45

Inspiratory reserve volume : Maximum volume of air you can breath in over and above normal inhalation

Question 46

Define the term 'Expiratory reserve volume' ?

Answer 46

Expiratory reserve volume : Maximum volume of air you can breath out over and above normal exhalation

Question 47

Define the term 'Residual volume' ?

Answer 47

Residual volume : Volume of air that reminds in the lungs following the strongest possible exhalation

Question 48

Define the term 'Total lung capacity' ?

Answer 48

Total lung capacity : Sum of the vital capacity and residual volume

Question 49

What is the breathing rate ?

Answer 49

The number of breaths taken per minute

Question 50

What is the ventilation rate ?

Answer 50

The total volume of air inhaled per minute

Question 51

What is the equation to calculate the ventilation rate ?

Answer 51

ventilation rate = tidal volume ( cm^3 ) x breathing rate ( /min )

Question 52

Explain the relationship between oxygen demands and tidal volume ?

Answer 52

- The tidal volume of air is moved in and out of lungs with each breath that increases ( eg. from 15 ---> 50 % of vital capacity ) - Breathing rate increases - Therefore ventilation rate increases, meaning Ov2 uptake increases to meet metabolic demands of tissue/ cells and provide Ov2 for aerobic respiration