3.1 - Exchange surfaces and breathing

Question 1

why are exchange surfaces needed? (Molecules)

Answer 1

• To take in and remove molecules (Take in O2 or glucose and get rid of waste products like CO2)

Question 2

If the surface area of an object is 12 and the volume is 4 what is the SA:Vol?

Answer 2

3:1

Question 3

How is the SA:Vol affected by the size of the object?

Answer 3

• As the object gets larger (normally) the SA:Vol decreases

- Smaller organisms often have a large SA:Vol but larger objects have a smaller SA:Vol

Question 4

How does the SA:Vol affect the need for an exchange surface in organisms?

Answer 4

Smaller organisms have a large SA:Vol meaning that diffusion is sufficient for gas exchange rather larger organisms have a smaller SA:Vol so they require exchange surfaces

Question 5

What is an example of an organism that does not require a specialised exchange surface?

Answer 5

An amoeba is less than 1mm in size meaning it has a high SA:Vol meaning diffusion is sufficient by itself
or a flatworm is similar however a flatworm is larger but has a much larger SA still

Question 6

How do levels of activity affect the need for an exchange surface?

Answer 6

Organisms that are more active have a higher metabolic rate meaning they are more in need of an exchange surface than organisms that are not as active and have a lower metabolic rate

Question 7

What are the characteristics of a good exchange system?

Answer 7

• A large surface area = More space across in which diffusion can take place
• A short diffusion distance = Increases the speed of diffusion from one place to another
• A good blood supply = Maintains the concentration gradient

Question 8

What are some examples of exchange surfaces?

Answer 8

• Intestines (Have microvilli)
• Lungs (Alveoli)
• Gills (Counter-current flow)
• The tracheal system in insects (Using tracheal fluid)
• Leaves (Have the stomata and spongy mesophyll)
• Root hair cells (Large SA)

Question 9

How would the lungs be labelled from top down?

Answer 9

• Trachea
• Ribcage and intercostal muscles lying between the ribs, surround the:
• x2 Bronchus
• Many bronchioles
• Many alveoli
• Pleural space outside of lungs but within the ribcage

Question 10

How is the trachea fit for function?

Answer 10

-Contains “C shaped” rings of cartilage to support it = keep the trachea open and stops the collapsing (the “C shape allows for flexibility when swallowing large quantities of food)

Question 11

Where does gas exchange occur in humans?

Answer 11

In respiratory bronchioles and the alveoli

Question 12

How are the bronchi fit for function?

Answer 12

• Contains goblet cells that secrete mucus
• Contains ciliated epithelial cells that wafts the mucus with particles up the trachea to be swallowed and neutralised by the stomach acid or expelled
• Contains smooth muscle that constricts the airways
• Contains connective tissue (with elastic fibres)
• Contains small blood vessels
• Contains “C shaped” cartilage

Question 13

How are the bronchioles fit for function?

Answer 13

• Contains smooth muscle that constricts to narrow the airways to stop harmful air from entering the alveoli
• Contains connective tissue (With elastic fibres)
• Contains ciliated epithelial cells that wafts the mucus with particles up the trachea to be swallowed and neutralised by the stomach acid or expelled

Question 14

How are the alveoli (air-sacs) fit for function?

Answer 14

• Have a dense network of capillaries that provides a good blood supply to maintain the concentration gradient
• Contains very large surface area due to lots of alveoli
• Contains squamous epithelial cells that are very thin meaning it provides a short diffusion distance
• Contains elastic fibres that work to re-inflate the airways in the alveoli

Question 15

What are the two movements of the diaphragm used to inflate/deflate the lungs?

Answer 15

• The diaphragm moves up when it is relaxed, this increases the pressure in the thorax so that air is forced out
• The diaphragm moves down when it is contracted, this decreases the pressure in the thorax so that air is forced in

Question 16

What occurs in the gas exchange in the alveoli?

Answer 16

• The oxygen from the air that is breathed in diffuses into the blood stream in the alveoli
• The Co2 is diffused out to be expelled during exhalation

Question 17

What is used to measure movement lung volume?

Answer 17

A spirometer

Question 18

What does the spirometer produce?

Answer 18

A spirometer trace, this shows a graph of volume of air

Question 19

What conditions must be set in place before using the spirometer?

Answer 19

• The user must be healthy (The user shouldn’t be someone with asthma)
• The mouth piece must be sterile (To prevent transmission of infections)
• The water must not be over-filled
• The oxygen must be fresh
• The soda lime must be fresh to absorb the CO2

Question 20

In what direction is the trace produced?

Answer 20

• The pen goes down when the participant inhales
• The pen goes up when the participant exhales
• The paper is then flipped upside down so that the trace displays the opposite (Down=exhale, Up=inhale)

Question 21

What is the tidal volume?

Answer 21

Everyday breathing rate (0.5dm3)

Question 22

What is the residual volume?

Answer 22

The volume left over after fully forcing expiration (1.5dm3)

Question 23

What is vital capacity?

Answer 23

The total volume in lungs between maximum inhale and maximum exhale (2.5 to 5dm3)

Question 24

What is vital capacity affected by?

Answer 24

• Fitness/exercise
• Age
• Size
• Gender
• Height

Question 25

How is oxygen uptake measured?

Answer 25

Using a spirometer trace to measure the tidal volume of a person over a longer amount of time (1 minute) - This is done by first filling the chamber with 100% oxygen - The person breathes in the oxygen and exhaling CO2 - CO2 is absorbed meaning the volume of gas in the chamber is decreasing as the O2 is being inhaled - This shows the decreasing rate of oxygen as oxygen uptake from the trace

Question 26

How is oxygen uptake calculated from the spirometer trace?

Answer 26

Pick two points at the same point of exhalation/inhalation but at different times: Point A- 4dm3 at 30 seconds Point B- 3dm3 at 60 seconds Work out the change in volume divided by the time Therefore 1dm3 in 30 seconds so 1dm3/0.5 =2dm3min-1

Question 27

Why does fish's gas exchange system have to be more efficient than humans?

Answer 27

Because there is a lower percentage of O2 in sea water (few mg of O2 per litre) than in the air (20% O2)

Question 28

How could you describe the gas exchange system in fish?

Answer 28

- Water enters the buccal cavity (mouth) - Water flows over the gill arch which contain blood vessels containing: - Oxygenated blood (goes back to the fish) - Deoxygenated blood (goes to gills to pick up O2)

Question 29

What are primary and secondary lamellae?

Answer 29

- Gill filaments (primary lamellae) are hair like structures attached to the gill arch - On the gill filaments are gill plates (secondary lamellae)

Question 30

What is the counter-current system in fish? | Describe it

Answer 30

- As deoxygenated blood enters and goes through the filaments water travels across the other way perpendicular to the deoxygenated blood - Blood then flows parallel to the water flow - This causes the oxygen to travel down the concentration gradient to the deoxygenated blood which becomes oxygenated - As the blood flows in the opposite direction to the water, it maintains the oxygen concentration as higher in the water meaning that the oxygen can still diffuse into the blood

Question 31

What is the graph that shows the counter-current flow

Answer 31

``` ^ | \ \ | \ \ Water | Blood \ \ | So blood is up and water is down \ \ | \ \ | v | ```

Question 32

What does the counter-current system in fish accomplish?

Answer 32

- Blood exits the gill filaments having extracted most of the O2 available - The counter-current flow maintains a concentration gradient all along the gill plate allowing more oxygen to be extracted

Question 33

How does a fish ventilate?

Answer 33

- Fish can move causing the water to go into the buccal cavity and through the gills e. g: Great white sharks are "obligate ram ventilators" meaning they rely on movement to ventilate and have water move through the gills - Some other fish's can open and close their buccal cavities which causes the gills to open and close making the water rush across them allowing oxygen to be extracted

Question 34

What is the insects equivalent of blood called?

Answer 34

Haemolymph, this fluid circulates around the body cavity without blood vessels

Question 35

What system supplies oxygen to the haemolymph in the body?

Answer 35

The tracheal system

Question 36

What is the tracheal system?

Answer 36

- Spiracle, external opening or pore - Trachea, supported by chitin - Tracheoles - Site of gas exchange, with tracheal fluid

Question 37

How is tracheal fluid used when the insect is inactive?

Answer 37

- When the insect is inactive there is a low demand for oxygen - This causes the tracheal fluid to leak into the tracheole meaning there is less surface area available for gas exchange - This means less water is lost out of the tracheoles

Question 38

How is tracheal fluid used when the insect is more active?

Answer 38

- When the insect is more active there is a higher demand for oxygen - This causes the tracheal fluid to be drawn out of the tracheole and into the tissues meaning there is a larger surface area for gas exchange - This means the insects may dry up more quickly

Question 39

How does a insects ventilate?

Answer 39

- Extremely active insects can flex their abdomen to increase ventilation - Movement of the flight muscles can increase the ventilation into and out the trachea - This is helpful as when flying, the insects are in need of more ventilation as they are more active - Locusts are able to actively ventilate to increase the movement of gases in the trachea. This is through the opening and closing of specific combinations of spiracles