Exchange Surfaces And Breathing ✅

Question 1

Why do multicellular organisms have evolved exchange surfaces

Answer 1

Metabolic activity is greater, more oxygen needs to be supplied and CO2 removed at higher rates

SA:V is smaller, diffusion alone would not achieve an adequate rate of gas exchange

Question 2

What are 4 features of exchange surfaces

Answer 2

Increases SA
Thin layers
Good blood supply
Good ventilation

Question 3

What are the benefits for each feature of exchange surfaces

Answer 3

Increased SA: overcome the reduced SA:V in larger organisms eg root hair cells

Thin layers: reduces the diffusion distance eg alveoli

Good blood supply and good ventilation: maintains steep concentration gradients through the quick supply and removal of gases eg gills/ alveolus

Question 4

In what order does the structures of mammalian gas exchange go in

Answer 4

Nasal cavity
Trachea
Bronchus
Bronchioles
Alveoli

Question 5

Key feature and function of nasal cavity

Answer 5

Good blood supply= warm air entering the body

Lined with hairs and mucus secreting cells= traps dust and bacteria

Moist surface= increases humidity, reducing evaporation from lungs

Question 6

Key features and function of trachea

Answer 6

Supported by flexible cartilage= prevents collapse

Lined with goblet cells which secretes mucus= traps dust and bacteria

Ciliated epithelium cells= cilia waft mucus away from the lungs

Question 7

Key features and function of bronchus

Answer 7

Cartilage, like the trachea= prevents collapse

Question 8

Key feature and function of bronchioles

Answer 8

Smooth muscle (no cartilage)= bronchioles can constrict and dilate to vary the amount of air reaching the lungs

Flattened epithelium cells= some gaseous exchange is possible

Question 9

Key features and function of alveoli

Answer 9

Single layer of flattened squamous epithelium cells= short diffusion pathway, which increases diffusion rate

Elastic Fibres and collagen= enable stretching and elastic recoil during ventilation

Large SA= increased rate of diffusion

Good blood supple (capillary network) and good ventilation= O2 supplied to alveoli and move into circulatory system quickly, CO2 supplied from circulatory system and removed form lungs quickly which maintains steep concentration gradient

Covered with a layer of surfactant= alveoli remain inflated

Question 10

What are goblet cells

Answer 10

line the airways and secrete mucus in order to trap any microorganisms and dust particles which have been inhaled

Question 11

What is cartilage

Answer 11

a type of smooth, elastic tissue that provides structural support to the body

Question 12

What is ciliated epithelium cells

Answer 12

column shaped cells, that cover many surfaces, contain cilia which beat in synchronized pattern to waft mucus away

Question 13

What is smooth muscle

Answer 13

Type of muscle tissue which allows constriction and can dilate

Question 14

What is elastic fibres in the trachea

Answer 14

The lungs inflate and the elastic fibres stretch in order to breathe out. The fibres recoil to push the air out when exhaling.

Question 15

What happens during inhalation

Answer 15

External intercostal muscles contract
Ribs move up and out
Diaphragm contracts and flattens
Thorax volume increases
Air pressure in lungs drops below atmospheric
Air moves into lungs

Question 16

What happens during exhalation

Answer 16

External intercostal muscles relax
Ribs move down and inwards
Diaphragm relaxes and reverts to it’s domed shape
Thorax volume decreases
Air pressure in lungs above atmospheric
Air moves out of lungs

Question 17

During forced exhalation what muscles contract

Answer 17

Internal intercostal muscles, abdominal muscles

Question 18

What’s a peak flow meter and spirometer

Answer 18

Peak flow: measures rate at which patients expel air into hand held tube used to monitor conditions eg asthma

Spirometer: can measure several aspects of lung volume

Question 19

What is total lung capacity, residual volume and vital capacity

Answer 19

Total lung capacity= Vital capacity+ residual volume

Residual volume= volume remaining in lungs after a person has exhaled with maximum force

Vital capacity= max volume that can be breathed out following strongest inhalation

Question 20

What is tidal volume and reserve volume

Answer 20

Tidal= volume inhaled with each resting breath/ exhaled with resting breath

Reserve= additional volumes of air that can be breathed in and out during forced inhalation and exhalation

Question 21

Why did insects gas exchange evolve differently to humans, so what do they do

Answer 21

Exoskeletons prevented diffusion of gas across insects body, lack blood pigments capable of transporting oxygen

They evolved a system of tubes (tracheae) that deliver oxygen directly to cells

Question 22

How does air enter an insect

Answer 22

Through small openings called spiracles

Spiracles are closed when possible to minimize water loss

Question 23

How does water enter and leave gills in a bony fish

Answer 23

Enters through mouth

Continuous flow of water across gills achieve by the floor of buccaneers cavity (mouth) being lowered (takes water in) and raised (forces water out)

Water leaves a fish when the operculum (flap covering the gills) opens

Question 24

How is oxygen taken up in an insect

Answer 24

Air travels through tracheae, branches into tracheoles

Oxygen diffuses into cells from tracheoles

Some active insects have high energy demand; they have evolved a muscular pumping system to increase O2 supply

Question 25

How is oxygen taken up in gills in bony fish

Answer 25

O2 diffuses into gill lamellae packed with blood capillaries. Lamellae are attached to gill filaments

Water and blood (in lamellae) flow in opposite directions (countercurrent flow). This ensures an O2 concentration gradient is maintained along the gill

Question 26

How’s does CO2 leave in an insect

Answer 26

CO2 diffuses from tissues into the tracheae down a concentration gradient

Question 27

Explain why multicellular organisms require specialized gas exchange surfaces (4 marks)

Answer 27

Relatively high metabolic rate (1)
Required greater oxygen supply and co2 removal (1)
Low SA:V ratio (1)
Means diffusion pathway is too long for diffusion alone to be effective (1)

Question 28

Describe how specialized gas exchange surfaces maintain concentration gradients to enable a high rate of diffusion (4marks)

Answer 28

Good blood supply ie dense capillary networks (1)
Removes oxygen and supply co2 at a high rate (1)
Good ventilation (1)
Supplies oxygen and removes co2 at a high rate (1)

Question 29

What happens to position of RBC during alveolar gas exchange

Answer 29

Compressed against capillary wall so closer to alveoli

Question 30

Where are the epithelial cells of alveolar

Answer 30

Outlines the alveoli

Question 31

State 3 features of alveoli that enable a high rate of gas exchange (3 marks, more then 3 available)

Answer 31

Short diffusion pathway due to flattened epithelia in alveoli (1)
And close proximity of alveoli and capillaries (1)
Large SA:V ratio (1)
Steep concentration gradient of O2 and CO2 (1)
Due to good blood supply, dense capillary network, (1)

Question 32

Table*
Explain why blood in pulmonary vein has the same partial pressure as the air in alveoli (2 marks)

Answer 32

Gases in the alveoli and alveolar capillaries/ pulmonary vein are at equilibrium (1)
Because gas exchange occurs until the concentrations on either side of the alveolar walls are equal (1)

Question 33

Table *
Suggest an explanation for the differences in partial pressure of O2 and CO2 in the pulmonary artery and alveolar air (2 marks)

Answer 33

The pulmonary artery carrie’s blood to the lung from tissues via the heart (1)
O2 concentration is lower and CO2 concentration is higher than in alveolar air because respiratory has happened in tissues (1)

Question 34

How does CO2 leave gills in bony fish

Answer 34

CO2 diffuses from capillaries across lamellae and into water which leaves through the operculum

Question 35

Explain why the evolution of a specialized gas exchange system was necessary for insects (2 marks)

Answer 35

Exoskeleton limits diffusion across body surfaces (1)
And some insects have relatively high energy requirements and therefore high O2 demand (1)

Question 36

Explain how structure of gills enables concentration gradients to be maintained dying gas exchange (3 marks)

Answer 36

Countercurrent flow (1)
Blood in capillaries and water flow in opposite directions (1)
O2 concentration is higher in the water than the capillaries along the length of the gills (1)